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To understand the basis of the resistance of pigeons to Asian lineage highly pathogenic avian influenza virus (HPAIV) subtype H5N1, we examined the presence of influenza virus receptors, sialic acids linked to galactose by an alpha-2,3 linkage (SAalpha2,3Gal) or by an alpha-2,6 linkage (SAalpha2,6Gal), in respiratory and intestinal tracts of pigeons and compared the distributions of N-acetylneuraminic and N-glycolylneuraminic acids in the trachea and intestines of pigeons and chickens. Results suggested that the epithelial surfaces of the larynx, trachea, bronchus, and bronchiole of pigeons contained abundant SAalpha2,6Gal with little or no SAalpha2,3Gal. In contrast, the epithelial surfaces of the pharynx, trachea, bronchus, and bronchiole of chickens contained mainly SAalpha2,3Gal, a well-recognized receptor for avian influenza viruses including H5N1 HPAIV. A similar distribution pattern of N-acetylneuraminic and N-glycolylneuraminic acids in the trachea and intestines of pigeons and chickens was observed. Overall, the results suggest that SAalpha2,6Gal is the major receptor in the pigeon airway, which may partly contribute to the resistance of pigeons to Asian lineage HPAIV subtype H5N1.

Glutamate transporter 1 (GLT1) in glial cells removes glutamate that diffuses from the synaptic cleft into the extracellular space. Previously, we have shown the distribution of glutamatergic neurons in the central nervous system (CNS) of the pigeon. In the present study, we identified cDNA sequence of the pigeon GLT1, and mapped the distribution of the mRNA-expressing cells in CNS to examine whether GLT1 is associated with glutamatergic terminal areas. The cDNA sequence of the pigeon GLT1 consisted of 1889bp nucleotides and the amino acids showed 97% and 87% identity to the chicken and human GLT1, respectively. In situ hybridization autoradiograms revealed GLT1 mRNA expression in glial cells and produced regional differences of GLT1 mRNA distribution in CNS. GLT1 mRNA was expressed preferentially in the pallium than the subpallium. Moderate expression was seen in the hyperpallium, Field L, mesopallium, and hippocampal formation. In the thalamus, moderate expression was found in the ovoidal nucleus, rotundal nucleus, triangular nucleus, and lateral spiriform nucleus, while the dorsal thalamic nuclei were weak. In the brainstem, the isthmic nuclei, optic tectum, vestibular nuclei, and cochlear nuclei expressed moderately, but the cerebellar cortex showed strong expression. Bergmann glial cells expressed GLT1 mRNA very strongly. The results indicate that cDNA sequence of the pigeon GLT1 is comparable with that of the mammalian GLT1, and a large number of GLT1 mRNA-expressing areas correspond with areas where AMPA-type glutamate receptors are located. Avian GLT1 in glial cells probably maintain microenvironment of glutamate concentration around synapses as in mammalian GLT1.

Feed manufacturing exerts physical and chemical changes in ingredients, including the gelatinisation of starch. Studies on the effect of the degree of starch gelatinisation on nutrient digestibility, metabolism and subsequent performance show inconsistent results, and no data are available in pigeons. In a cross-over trial, fourteen adult pigeons were randomly divided into two groups, in which two extruded pellet diets were tested. Both the diets were similar in ingredient composition and nutrient content, but differed in extrusion conditions, resulting in a different degree of starch gelatinisation: pellets with high gelatinisation degree (HG; 73.6% gelatinisation) and low gelatinisation degree (LG; 53.1% gelatinisation). After a 14-day adaptation period, all excreta were gathered per bird during a 5-day collection period. Coefficients of apparent digestibility of dry matter (DM), crude protein (CP), ether extract (EE), crude fibre (CF), crude ash (CA) and nitrogen free extract (NFE) as well as apparent nitrogen retention were calculated from proximate analyses of feed and excreta. Further, excreta consistency was subjectively scored. Blood samples were taken at the end of each period and plasma samples were analysed for glucose, fructosamine and triglycerides. Feed intake and body weight changes were recorded weekly. The apparent digestibility coefficients (ADCs) of DM, OM, CP, EE, CA and NFE were significantly higher in the LG group (p < or = 0.05). The ADC of crude fibre was numerically higher in the LG group but not significant, and no significant differences were found in starch digestibility. Excreta consistency score tended to be higher in the LG diet group. Neither plasma glucose nor plasma fructosamine values were significantly different between the two test diets. The results of this study show that lower degree of starch gelatinisation in extruded diets can enhance digestibility in pigeons.

Pigeons were divided into two numerically equal groups (A and B) containing 30 specimens each. Birds from group A were intraperitoneally injected daily with 0.1 mL/100 g body wt of vehicle (0.1 M acetate buffer, pH 4.3 containing 0.1% gelatin). Specimens from group B were intraperitoneally injected daily with 1 microg/100 g body wt of salmon calcitonin. Six birds were sacrificed from each group 2 h after the last injection on 1st, 3rd, 5th, 10th, and 15th day of the experiment. After collection of blood samples, ultimobranchial and parathyroid glands were fixed for histological studies. In calcitonin-treated C. livia, the plasma calcium levels exhibit a progressive decline from day 1 till day 5. On day 15, the levels become more or less similar to the control value. No change has been noticed on day 1 in the plasma phosphate levels of calcitonin-treated C. livia. The levels decrease progressively from day 3 to day 5; thereafter, it exhibits an elevation so that on day 15, normal plasma phosphate levels is achieved. The ultimobranchial gland of C. livia exhibits no change up to day 5 following calcitonin treatment. The nuclear volume of ultimobranchial cells exhibits a decrease on day 10. This response progresses up to day 15. Few degenerating cells are also discerned following 15 days calcitonin treatment. The parathyroid gland of calcitonin-treated C. livia exhibits no histological alteration up to day 3. The nuclear volume of parathyroidal cells exhibits a progressive increase from day 3 till the close of the experiment (day 15). Moreover, the gland exhibits more compactness on day 10 and day 15. Few degenerating cells are encountered after day 15 following calcitonin treatment., ((c) 2008 Wiley-Liss, Inc.)

In the avian brain, the optokinetic response is controlled by two retinal-recipient nuclei: the nucleus of the basal optic root (nBOR) of the accessory optic system and the pretectal nucleus lentiformis mesencephali (LM). Although considered sister nuclei because of their similar response properties and function, there are both similarities and differences with respect to efferent projections and neurochemistry. Both nBOR and LM project to the cerebellum (Cb) directly as mossy fibers but also indirectly via the inferior olive (IO). In a previous report, we showed that the cerebellar- and inferior olivary-projecting neurons in nBOR of pigeons differentially express the calcium-binding proteins calretinin (CR) and parvalbumin (PV). Both CR and PV are expressed in the somata of LM neurons, although the latter is not as prevalent, and whether expression of CR and PV reflects cerebellar and IO projections is not known. In this report, by combining retrograde neuronal tracing from the Cb and IO with fluorescent immunohistochemistry, we examined the expression of these calcium-binding proteins in the pigeon LM. Half (52%) of the cerebellar-projecting neurons were CR+ve, but only 15% were PV+ve. Almost all (>95%) these PV+ve cells also expressed CR. In contrast, few of the IO-projecting neurons expressed CR or PV (

1. The pharmacokinetics of florfenicol were investigated in chickens (n = 20), pigeons (n = 30) and quails (n = 60) following intravenous (i.v.) and intramuscular (i.m.) administration of 30 mg/kg body weight. The concentration of florfenicol was measured using high performance liquid chromatography with ultraviolet detection. 2. The plasma concentrations following administration of the drug by both routes were lower in pigeons and quails than in chickens for the whole sampling period. 3. Following i.v. administration, plasma concentration over time was best described by a two-compartment open model. The elimination half-life (t(1/2)(beta)), mean residence time (MRT), total body clearance (Cl(B)), area under the plasma concentration curve (AUC(0-infinity)) were different in chickens, pigeons and quail. The distribution half-life (t((1/2))(alpha)) and volume of distribution (V(dss)) were similar in all species studied. 4. Plasma concentration time data after i.m. administration was adequately described by one-compartment open model. The elimination half-life (t((1/2)el)), mean residence time (MRT), maximum plasma concentration (C(max)) and area under the plasma concentration curve (AUC(0-infinity)) were significantly different in chickens, pigeons and quail. Mean absorption time (MAT), time to maximum concentration (T(max)), absorption half-life (t((1/2)ab)) and systemic bioavailability (F) were similar in the three species. 5. Species differences in florfenicol elimination exist. Doses and treatments should not be extrapolated from chickens to pigeons and quails without pharmacokinetic data.

Glutamate acts as the excitatory neurotransmitter in the central nervous system (CNS) and is mediated largely by the vesicular glutamate transporters (VGLUT1-3) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) types of glutamate receptors (GluR1-4) in mammals. In the present study, we determined the cDNA sequences of pigeon VGLUT2 and GluR1 and mapped the distribution of their mRNA in the pigeon CNS. The predicted amino acids of pigeon VGLUT2 and GluR1 showed a 93% identity to human VGLUT2 and GluR1 both. In situ hybridization autoradiograms showed VGLUT2 mRNA expression exclusively in the pallium of the telencephalon, and no expression in the subpallium. Within the diencephalon, VGLUT2 mRNA was more abundant in the thalamus than in the hypothalamus. Rich VGLUT2 mRNA expression was found in the optic tectum, nucleus mesencephalicus lateralis, pars dorsalis, nucleus isthmi, pars parvocellularis, isthmo-optic nucleus, pontine nuclei, and granular layer of the cerebellum. Moderate expression was noted in the cerebellar nuclei, vestibular nuclei, cochlear nuclei, inferior olivary nucleus, and gray matter of the spinal cord. GluR1 mRNA was expressed abundantly in the pallium and subpallium of the telencephalon, but it was poor in the diencephalon, midbrain, medulla, cerebellar cortex, and gray matter of the spinal cord. These results suggest that the cDNA sequences of VGLUT2 and GluR1 in the pigeon are comparable to those of VGLUT2 and GluR1 in mammals, respectively. The distribution of pigeon GluR1 mRNA resembles that of mammals, but the distribution of VGLUT2 mRNA resembles that of both VGLUT1 and VGLUT2 in mammals., (Copyright 2008 Wiley-Liss, Inc.)

Many birds and mammals show changes in the hypothalamo-pituitary-gonadal (HPG) axis in response to social or sexual interactions between breeding partners. While alterations in GnRH neuronal activity play an important role in stimulating these changes, it remains unclear if acute behaviorally-induced alterations in GnRH release are accompanied by parallel changes in GnRH synthesis. To investigate this relationship, we examined changes in the activity of GnRH neurons in the brains of male ring doves following brief periods of courtship interactions with females. Such interactions have been previously shown to increase plasma LH in courting male doves at 24 h, but not at 1 h, after pairing with females. In the first study, males allowed to court females for 2 h had 60% more cells that showed immunocytochemical labeling for GnRH-I in the preoptic area (POA) of the hypothalamus than did control males that remained isolated from females. To determine whether an increase in GnRH gene expression preceded this increase in GnRH immunoreactivity in the POA, changes in the number of cells with detectable GnRH-I mRNA in the POA were measured by in situ hybridization following a 1 h period of courtship interactions with females. In this second study, courting males exhibited 40% more cells with GnRH-I in this region than did isolated control males. GnRH-immunoreactive neurons in two other diencephalic regions failed to show these courtship-induced changes. Plasma LH was not elevated after 1 or 2 h of courtship. These results demonstrate that the release of GnRH-I in the POA that is presumably responsible for courtship-induced pituitary and gonadal activation is accompanied by a rapid increase in GnRH synthesis that occurs before plasma LH levels increase. We suggest that this increase in GnRH synthesis is necessary to support the extended period of HPG axis activation that is seen in this species during the 5-10 day period of courtship and nest building activity.

Pigeons are used frequently as subjects in behavioral pharmacology research. An advantage of the pigeon is an exceedingly vascular breast muscle, which is easily accessible for injections. The purpose of these studies was to provide a profile of the pharmacokinetics of (+)-methamphetamine (METH) and (+)-amphetamine (AMP), a pharmacologically active metabolite, in pigeons (n=6) after intramuscular (i.m.) and intravenous (i.v.) dosing (0.8 mg/kg). LC-MS/MS analysis was used to determine serum concentrations of METH and AMP. A modified crossover design was used to determine the bioavailability, time to maximum concentration, total clearance, the volume of distribution, the maximal concentration, the area under the concentration-time curve (AUC), and terminal elimination half-life for METH. The route of administration did not significantly affect these pharmacokinetic parameters. The time to maximum concentration for METH and AMP following i.m. administration was 0.3 h. Maximum AMP serum concentrations were achieved in 2 h, irrespective of the route of administration, and these concentrations remained essentially constant for an additional 6 h. The metabolism of METH to AMP was not affected by the route of administration, and the molar ratio AMP to METH AUC values were the same (i.v.=0.57; i.m.=0.41). These results show that METH pharmacokinetics after i.m. administration in the pigeon are similar to i.v. administration. Thus i.m. is a reasonable route of administration for METH behavioral assays in the pigeon if sufficient time for absorption is given following the dose, and the behavioral endpoint is not dependent on the rapid input of METH following an i.v. dose.

Oxidative stress, an imbalance between endogenous levels of oxygen radicals and antioxidative defense, increases with aging. However, it is not clear which of these two factors is the more critical. To clarify the production of oxygen radicals increases with age, we examined oxygen radical-dependent chemiluminescent signals in ex vivo brain slices using a novel photonic imaging method. The chemiluminescent intensity was significantly decreased by the membrane permeable superoxide dismutase (SOD)/catalase mimic, but not by Cu,Zn-SOD. Inhibitors for complex I, III, and IV of the mitochondrial electron transport chain transiently enhanced the chemiluminescent signal. The superoxide-dependent chemiluminescent intensity in senescence accelerated mouse (SAM) brain tissues increases with age. Moreover, the slope of the age-dependent increase was steeper in SAMP10, a strain characterized by a short lifespan and atrophy in the frontal cerebral cortex, than the senescence-resistant strain SAMR1, which has a longer lifespan. An increase in chemiluminescence with age was also observed in C57/BL6 mice, Wistar rats, and pigeons, although levels of chemiluminescence were lower in the pigeons than murines. The rate of age-related increases of superoxide-dependent chemiluminescence was inversely related to the maximum lifespan of the animals. The activity of superoxide dismutase was unchanged during the aging process in the brain. This suggested that superoxide production itself may increase with age. We speculated that reactive oxygen may be a signal to determine the aging process.

In the present study, the acute behavioral and ingestive effects of ICV injections of mammalian orexin-A (ORXA; vehicle, 0.2, 0.6 or 2 nmol) and of orexin-B (ORXB; vehicle, 0.2, 0.6 or 2 nmol), as well as possible long-term effects (through 24 h of continuous intake monitoring after 0.6 nmol of ORXA or ORXB) of these treatments in food/water intake and in blood levels of metabolic fuels (free fatty acids and glucose, after 0.2 or 0.6 nmol of ORXA) were examined in adult male pigeons. Both ORXA and ORXB treatments failed to produce acute (1-3 h) or long-term effects on feeding and drinking behaviors, and did not change blood free fatty acids and glucose 15 and 30 min after treatments, as compared to vehicle-treated animals. However, ORXA (but not ORXB) treatments evoked a dose-related, intense increase in exploratory behaviors, associated to reduced time spent in alert immobility and sleep-typical postures. These data substantiate the lack of orexigenic effects of ORXs in avian species, and suggest that an important role in vigilance control may represent a conserved functional attribute of orexinergic circuits in vertebrates.

A sensitive ELISA was developed for the detection of amoxicillin (AMX) in serum, urine, and milk. The ELISA used an indirect competitive method produced by coating the plate with ovalbumin conjugated with AMX hapten. Antibodies against AMX-BSA were detected by a goat-antirabbit antibody conjugated with peroxidase. Calibration standard curves ranged from 1.28 ng/mL to 20 microg/mL [IC(50) (inhibition concentration 50%) = 100 ng/mL], and the limits of detection were 1.3, 2.7, and 4.8 ng/mL for urine, milk, and serum, respectively. The intra- and interassay variations were less than 4 and 9.6%. The antibody produced against AMX cross-reacted highly with penicillin G (77%); cross-reacted moderately with ampicillin, oxacillin, and cloxacillin (56.9, 51.4, and 48.8%, respectively); but was considered non-cross-reactive with dicloxacillin (7.4%), cefadroxil (<1%), and cefazolin (<1%). Concentrations of AMX were measured simultaneously in venous blood and muscles by using the developed AMX ELISA in an in vivo microdialysis model designed for pigeons. Following i.m. injection (25 mg/kg), AMX attained a peak blood level of 4.74 +/-0.30 mu g/mL and decreased with a half-life of 2.38 +/-0.16 h. In contrast, measurements in pectoral and femoral muscles exhibited delayed appearances, reduced peak concentrations, and prolonged half-lives of 4.07 +/-0.48 (pectoral) and 3.01 +/-0.26 (femoral) that were significantly different from each other and those in the blood (P < 0.05). Blood protein binding was calculated to be 27.9 +/-5.7%. This study demonstrated the semiquantitative application of a selective AMX ELISA in the first microdialysis procedure for continuous monitoring of drug levels in specific tissues of pigeons and maybe useful for related studies in other poultry species.

The Pin-tailed Manakin (Ilicura militaris) is a small, sexually dimorphic, frugivorous suboscine songbird (Pipridae; Passeriformes; Aves) endemic to the Atlantic Forest of Brazil. A variant individual of this species was recently described in which the red patches that characterise the male's Definitive plumage were replaced by orange-yellow ones. We show here that the pigments in the feathers of the colour variant are common dietary carotenoids (zeaxanthin, beta-cryptoxanthin), not carotenoids synthesised by birds, lending support to the suggestion that the individual is a colour mutant lacking the capability to transform yellow dietary pigments into the red pigments normally present in these feathers. By comparison, the yellow crown feathers of a close relative, the Golden-winged Manakin (Masius chrysopterus), contained predominantly endogenously produced epsilon-caroten-3'-ones. Surprisingly, the normal-coloured feathers of the male Pin-tailed Manakin owe their red hue to rhodoxanthin, an unusual carotenoid more commonly found in plants, rather than 4-keto-carotenoids typically found in red plumages and found lacking in previously characterised bird colour variants. The implication is that birds, like the tilapia fish, may be able to synthesise this unusual pigment endogenously from dietary precursors. A newly described carotenoid, 6-hydroxy-epsilon,epsilon-carotene-3,3'-dione, here named piprixanthin, present in the red feathers of the Pin-tailed Manakin, provides a plausible intermediate between epsilon,epsilon-carotene-3,3'-dione (canary-xanthophyll B), a bright yellow pigment found in this and other songbirds, and rhodoxanthin. It is apparent that pigeons (Columbidae, Columbiformes) also have the capability to produce rhodoxanthin, and a structurally related pigment, endogenously. The ability to synthesise rhodoxanthin might have arisen at least twice in birds.

To determine if blood administered to pigeons by gavage tube would simulate gastrointestinal hemorrhage in a noncarnivorous avian model, be digested in the gastrointestinal tract, and subsequently alter concentrations of plasma urea nitrogen, creatinine, or uric acid, blood from common peacocks (Pavo cristatus) was administered by gavage tube to 5 healthy domestic pigeons (Columba livia) at doses of 0.5, 1.0, 2.0, 4.0, and 8.0 ml/kg. No significant difference in plasma concentrations of urea nitrogen, creatinine, or uric acid was seen 4-6 hours after gavage. The findings did not support or rule out the presence of gastrointestinal blood in pigeons as a model for hemorrhage in noncarnivorous avian species.

The heart, red skeletal muscles and the nitrogen-fixing legume root nodule function in steady states of high oxygen influx, partial oxygenation of cytoplasmic myoglobin or leghemoglobin and correspondingly low oxygen partial pressure. Here, we ask: what conditions are required at the surface of actively respiring, state III, tightly coupled mitochondria to enhance oxygen flow to cytochrome oxidase? Pigeon heart mitochondria were isolated with minimal damage to the outer mitochondrial membrane and were incubated at low oxygen pressures, where respiration is oxygen limited, with solutions of each of six monomeric hemoglobins with widely divergent kinetics and equilibria in their reactions with oxygen: Busycon myoglobin, horse myoglobin, Lucina hemoglobins I and II, soybean leghemoglobin c and Gasterophilus hemoglobin. Each augments oxygen uptake. The declining fractional saturation of each hemoglobin with oxygen was monitored spectrophotometrically as mitochondrial respiration depleted the oxygen; the oxygen partial pressure at half-maximal rate of oxygen uptake was similar for each hemoglobin, supporting the conclusion that the hemoglobins did not interact with the mitochondrial surface in oxygen delivery. The oxygen pressure required to support state III mitochondrial oxygen uptake, 0.005 kPa (0.04 torr), is small compared with that obtained in the sarcoplasm and at the mitochondrial surface of the working heart, 0.32 kPa (2.4 torr). We conclude that, in normal steady states of contraction of the myoglobin-containing heart, oxygen utilization by mitochondrial cytochrome oxidase is not limited by oxygen availability.

The sleep promoting functions of melatonin have gained wide scientific attention due to the ability of this indole to provide relief from sleep inefficiency and the temporal relationship between its nocturnal rise in the blood and the "opening of the sleep gate" at night. However, little is known about the effects exerted by its precursor, the amino acid tryptophan. We studied the effect of a 7-day administration of two concentrations of tryptophan (125 and 300 kg b.w.) on the activity/rest rhythms of ringdove, aged 2-3 (young) and 10-12 (old) years, and on the serum levels of serotonin and melatonin. Activity pulses were logged before, during, and up to 5 days after the treatments. The animals received 125 or 300 mg/kg b.w. per animal/day at 09:00 h or at 19:00 h. Subsequently we chose the treatment which gave the best results in terms of nocturnal rest without affecting diurnal activity, i.e., 300 mg/kg b.w. administered to old animals at 09:00 h, 1 h after lights on, for the serotonin and melatonin measurements. During this treatment, the nocturnal and diurnal levels and amplitudes of serotonin and melatonin were all significantly higher than the corresponding levels before and after the treatment. In sum, our results point to an improvement of nocturnal rest in this animal model of old ringdove when administering 300 mg/kg tryptophan 1 h after lights on.

Like lactating mammals, male and female ring dove parents increase their food consumption to meet the energetic challenges of provisioning their young. To clarify the neurochemical mechanisms involved, the present study investigated the relationship between parental hyperphagia and changes in activity of the potent orexigen neuropeptide Y (NPY) in the hypothalamus of breeding doves. Changes in NPY-immunoreactive (NPY-ir) cell numbers in the tuberal hypothalamus of male and female doves were examined by immunocytochemistry at six stages of the breeding cycle. Parallel NPY mRNA measurements were recorded in mediobasal hypothalamus (which includes the tuberal hypothalamus) by semiquantitative reverse transcription-polymerase chain reaction using 18S rRNA as the internal standard. NPY mRNA changes were also measured in the mediobasal hypothalamus of nonbreeding doves following intracranial administration of prolactin, an orexigenic hormone that is elevated in the plasma of parent doves, and in response to food deprivation, which mimics the negative energy state that develops in parents as they provision their growing young. NPY-ir cell numbers in the tuberal hypothalamus and NPY mRNA levels in the mediobasal hypothalamus were significantly higher in breeding males and females during the period of parental hyperphagia after hatching than during the late incubation period when food intake remains unchanged. In nonbreeding doves, food deprivation and prolactin treatment increased NPY mRNA in this region by two- to three-fold, which suggests that NPY expression is sensitive to hormonal and metabolic signals associated with parenting. We conclude that NPY synthesis is increased in the mediobasal hypothalamus during the posthatching period, which presumably supports increased NPY release and resulting parental hyperphagia. NPY-ir and mRNA were also high in the mediobasal hypothalamus prior to egg laying when food intake remained unchanged. Several lines of evidence suggest that this elevation in NPY supports the increased gonadal activity that accompanies intense courtship and nest building interactions in breeding doves.

The essential amino acid tryptophan is the precursor in the anabolic pathway of melatonin, a hormone with immunomodulatory properties. The present study shows the in vivo effect of tryptophan on the phagocytic function and oxidative metabolism of heterophils from Streptopelia roseogrisea of < 1 year of age, with a parallel evaluation of the plasma levels of melatonin. The L-tryptophan was administered orally (125 and 300 mg/kg b.w.) at 19:00, before the beginning of the period of darkness, for 7 days. At the end of the tryptophan treatment, determinations were made at 21:00 and 02:00 of the Phagocytosis Index, the Phagocytosis Percentage, the Phagocytic Efficiency and the superoxide anion levels in heterophils isolated from blood and of the plasma levels of melatonin. The results showed, for the determinations at 21:00 in the animals that had received 125 mg L-tryptophan/kg b.w., enhanced heterophil phagocytic function and raised levels of plasma melatonin, with no affect on the oxidative metabolism of the phagocytes. For the administration of the greater concentration of tryptophan (300 mg/kg b.w.), there were raised plasma melatonin levels together with increases in heterophil phagocytic capacity and phagocyte oxidative metabolism at 02:00. The results indicate that tryptophan administered orally at night to diurnal animals of less than 1 year in age affects the circulating levels of melatonin at the same time as inducing stimulation of the innate immune function.

This study examined the ingestive and behavioral effects of NMDA- and AMPA/kainate glutamatergic receptor blockade in the lateral hypothalamic area (LHy) of free-feeding pigeons (Columba livia). Injections of MK-801 (NMDA receptor antagonist; 6 nmol) or CNQX (AMPA/kainate receptor antagonist; 25.8 nmol) into the LHy of free-feeding pigeons induced significant increases in food intake and in feeding duration, as well as reductions in the latency to start feeding. Duration, latency and volume of water intake, as well as duration of sleep-like behavior, alert immobility, locomotion and preening were not changed by these treatments in the LHy. These results indicate that glutamatergic inputs to cells containing NMDA and/or AMPA receptors located in the LHy could modify both the beginning of a feeding bout (or the end of a period of satiety) and its duration (satiation). Our data also suggest that these inhibitory glutamatergic influences on feeding behavior are tonically active in the LHy.

This study examined possible routes for lead (Pb) accumulation in resident pigeons collected from rural, urban, and four industrial sites in Korea. The accumulation pattern of Pb was comparable to the study sites. The highest Pb concentration was found in the bone, followed by kidney, liver, and lung of pigeons. Highest Pb residues in bones were found in urban (Seoul), and two industrial complex areas (Busan and Ulsan), which were about 15 times higher than rural area (Duckjuk island), and followed by Ansan and Yochon industrial areas. Regional Pb variations in liver, kidney, and lung tissues were also similar pattern with the bone Pb difference. These findings indicate that Pb accumulation in tissues of pigeons may be affected by the Pb exposure in their respective habitats. Crop contents and gizzard materials were investigated as representing the ingested items. No difference of Pb concentration was observed in major foods (maize and/or wheat) of crop contents in the study sites except Busan, whereas variations of Pb levels in gizzard materials were indicative of a similar pattern with tissue Pb differences. The Pb concentration in tissues of pigeons did not correspond well to the atmospheric Pb levels. With regard to possible Pb sources, ingested items especially materials present in the gizzard are important sources for Pb contamination to pigeons because Pb-containing sources may be expected to present in roadside particles, dusts, paint chips and building flakes. However, air Pb value being low may not affect significant as the regional variations in tissues of pigeons.

Artery smooth muscle cell proliferation is of key importance in the development of atherosclerosis and restenosis following PTCA. In order to understand gene regulation involved in these processes, vascular smooth muscle cells (VSMCs) from atherosclerosis-susceptible White Carneau (WC) and atherosclerosis-resistant Show Racer (SR) pigeons were used to identify transcription factors involved in the enhanced proliferation of WC VSMCs. With protein/DNA array, signal transducer and activator of transcription 4 (STAT4) was found to have over a 10-fold increase in expression in WC compared to SR VSMCs. The difference was confirmed with electrophoretic-mobility shift assay (EMSA) and Western blot. Cells cultured under low serum had 5-fold higher levels of STAT4 in WC compared to SR. By Western analysis, aortic tissue from newly hatched WC pigeons had 1.7-2.0 times greater STAT4 expression than in SR pigeons. A pathway whereby enhanced STAT4 may be associated with enhanced proliferation was identified following IL-12 stimulation of WC VSMCs where 3-fold increases in proliferation and 2-fold higher expression of STAT4 were measured. The findings suggest STAT4 may play a role in VSMC proliferation and describe a unique pigeon model system in which to study STAT4 as a gene target for atherosclerosis therapy.

Birds have much higher plasma glucose and fatty acid levels compared to mammals. In addition, they are resistant to insulin-induced decreases in blood glucose. Recent studies have demonstrated that decreasing fatty acid utilization alleviates insulin resistance in mammals, thereby decreasing plasma glucose levels. This has yet to be examined in birds. In the present study, the levels of glucose and beta-hydroxybutyrate (BOHB), a major ketone body and indicator of fatty acid utilization, were measured after the administration of chicken insulin, acipimox (an anti-lipolytic agent), or insulin and acipimox in mourning doves (Zenaidura macroura). Insulin significantly decreased whole blood glucose levels (19%), but had no effect on BOHB concentrations. In contrast, acipimox decreased blood BOHB levels by 41%, but had no effect on whole blood glucose. In addition to changes in blood composition, levels of glucose uptake by various tissues were measured after the individual and combined administration of insulin and acipimox. Under basal conditions, the uptake of glucose appeared to be greatest in the kidney followed by the brain and skeletal muscle with negligible uptake by heart, liver and adipose tissues. Acipimox significantly decreased glucose uptake by brain (58% in cortex and 55% in cerebellum). No significant effect of acipimox was observed in other tissues. In summary, the acute inhibition of lipolysis had no effect on glucose uptake in the presence or absence of insulin. This suggests that free fatty acids alone may not be contributing to insulin resistance in birds.

Alterations in the function of the hypothalamic suprachiasmatic nucleus (SCN) with age have been reported. As serotonin is an important regulator of the circadian clock located in SCN, this work studied the changes produced in the synthesis of serotonin with age using the accumulation of 5-HTP after decarboxylase inhibition as a measure of serotonin synthesis in the brain in vivo, in young and old ring doves at the onset of lights-on and lights-off. A diurnal cycle in tryptophan hydroxylation was observed in young animals, with an increased daylight synthesis and metabolism of 5-HT in hippocampus, neostriatum and hypothalamus. A single dose of melatonin (1 mg/kg, i.p., 1 h) at lighttime produced an inhibitory effect on the synthesis of 5-HT. In contrast, differences in 5-HT synthesis and metabolism between day and night disappeared in old animals indicating an absence of a circadian rhythm in 5-HT synthesis and metabolism. The administration of L-tryptophan (240 mg/kg, i.p.) strongly increased the 5-HT synthesis in young animals only during lights-off time while it increased in old ones irrespective of the administration time. These results suggest that the supplemental administration of tryptophan might aid to improve the descent in 5-HT that normally occurs, as animals get old.

The population of peregrine falcon (Falco peregrinus sbs. brookei) inhabiting the Regional Park of southeastern Madrid (RPSM), Spain, has experienced an increase of unsuccessful pairs (from 15% among a total of 20 pairs in 1995 to 55% among a total of 18 pairs in 2001). Traditionally, this area has been known to be contaminated with organochlorine compounds and toxic metals, which are known to be deleterious to the reproductive system of birds. During the breeding seasons of 2000 and 2001, contaminant residues were measured in unhatched eggs of peregrine falcons and liver of their main prey, to determine if they could be affecting the survival of the population. The most abundant contaminants were ortho-polychlorinated biphenyls (ortho-PCBs), ranging from 202.56 to 3,335.16 ng/g (wet wt) in falcon eggs and from 10.25 to 53.51 ng/g (wet wt) in pigeon livers. In all samples, the 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were detected, although these levels never exceeded 20 pg/g (wet wt). The major contributor to total toxic equivalent quantities (TEQs) were non-ortho-PCBs. Organochlorine levels found in this study may contribute to the entire suite of stressors that are negatively affecting the peregrine population.

Numerous recent studies have shown the ability of physiological as well as all pharmacological concentrations of melatonin to prevent oxidative stress. We have found that incubating avian heterophils from young birds with a pharmacological concentration of 100 microM (23x10(6) pg/ml) melatonin reduced superoxide anion levels by modulating the activity of superoxide dismutase while also enhancing phagocytosis. There was also a decline in lipid peroxidation levels with both physiological and pharmacological concentrations of this indolamine. In the present work, we evaluated malonaldehyde (MDA) levels as an indicator of lipid peroxidation (both basal and antigen-induced) in young and old animals (ring doves) at different times of day (16:00 and 00:00) and with two incubation times (15 and 60 min). The lipid peroxidation was also measured in heterophils from old animals, incubated with the physiological concentrations of melatonin measured in young animals (50 and 300 pg/ml, diurnal and nocturnal, respectively). The results, expressed as nmol MDA/mg protein, show that MDA levels were higher in heterophils of old animals than in the young birds in all the experimental groups studied at both 16:00 and 00:00 (00:00 is the time at which the lowest peroxidation levels were obtained). Incubation with melatonin was found to reduce MDA levels, with the maximum reduction being after the 60?min incubation time and the nocturnal melatonin concentration. At both concentrations (diurnal and nocturnal), melatonin also counteracted the enhancement of MDA levels caused by latex beads, with the effect being greater at the longer incubation time. In conclusion, the results are further evidence of the antioxidant effect of melatonin even at physiological concentrations, and suggest its utility as a therapeutic agent in some pathological processes associated with age.

Potassium ions are a prerequisite for the development and regulation of sensory cell stimulation in the inner ear. From the potassium-rich endolymph the ions flow into the sensory cells apically and are released basolaterally. After transport pathways of various lengths potassium is released again into the endolymph - in the cochlea by marginal cells of the stria vascularis, in the vestibular labyrinth by dark cells. While this long recycling pathway is relatively well-known in the cochlea, few studies have been conducted on the semicircular canal ampullae (SCCA) where its morphological basis is largely unknown. According to the present electron microscopic findings, potassium ions are initially released into the extracellular space during stimulation of the sensory cells and then absorbed by supporting and light cells. Finally they are transported transcellularly over numerous very long gap junctions into the region of the dark cells. From here they move to an extracellular compartment, which is more or less completely sealed off basally by basal plates of the light cells. Apically the intercellular space between light and dark cells is sealed by junctional complexes. This newly identified space in the SCCA corresponds to the extracellular compartment between the marginal and intermediate cells in the stria vascularis. At both sites, the cochlea and the SCCA, this probably serves as a regulatory valve, reservoir or storage space, particularly for potassium ions. It is likely that the different morphology of the ion transport pathways is related to the different flow levels of potassium ions expressed by the different levels of the so-called endocochlear potential and concomitant movement of other ions in the cochlea and SCCA.

The uropygial gland is a holocrine secretory gland of birds. The lipid and the waxy sebum that the gland secretes is coated on the beak and transferred to the plumage in preening. The composition of the gland secretions from birds of different species has been determined, but little is known about the lipids of the secretion of the gland of the rock dove Columba livia. The amount of secretion, the total lipid content and the fatty acids composition of the secretion of C. livia captured in the nonbreeding season was reported. The mean amount of the secretion within the gland was 30 mg; the mean lipid content of the secretion was 0.385 mg/mg of secretion, which was equivalent to approximately 38% of the secretion. The weight of the secretion relative to gland weight was 32%. If we assume that the amount of the gland secretion constitutes a valid parameter to determine the degree of the gland development, our results indicate that the physiological role of the gland does not depend upon gland mass (GW); the rock dove in particular has a small gland, but its secretion represented 32% of the gland's mass. The composition of the lipids extracted from the gland secretion consisted of C14 to C20 fatty acids, most of them were unsaturated. The secretion of the gland contained approximately 59% of unsaturated fatty acids with a prevalence of oleic acid (37%) and a low content of linoleic (6%) and arachidonic acids (7%). The saturated long chain fatty acids were mainly 14:0, 16:0 and 18:0 in a percentage of approximately 34%. No sexual differences were found in any of the evaluated parameters.

The presence and cell localization of TrkB, the main receptor for the neurotrophins (NTs), was investigated immunohistochemically in the small intestine of adult pigeons, with special reference to the enteric nervous system (ENS). Several neuronal (neurofilament proteins and PGP 9.5) and glial cell (S100 protein) markers were studied in parallel. TrkB immunoreactivity (TrkB-IR) was found to be restricted to immunohistochemically-identified glial cells present in the enteric plexuses, and to Schwann cells forming the perivascular plexus. Also, TrkB-IR was detected in enterochromaffin cells and in unidentified dendritic cells within the gut-associated lymphoid tissue. The present results demonstrate that as for mammals, TrkB in the ENS is restricted to the glial cells. The possible function of the TrkB ligands, however, remains to be established.

The protective effects of various divalent cations against the irreversible damage of myocardium, a phenomenon termed "the Ca2+-paradox", were examined in the isolated perfused pigeon heart. All cations examined were added at a concentration of 200 micromol l(-1) in the "calcium-free" medium. In hearts perfused with low calcium, upon normal calcium repletion, the maximal recovery of the contractile tension (in the 2nd minute) was approximately 115% and the recovery obtained at the end of reperfusion was 81.5% (compared to the equilibration period value). From the other divalent cations examined, the presence of cobalt, nickel, manganese or barium during calcium depletion powerfully protected the pigeon heart. Upon calcium repletion, the maximal recovery of contractile tension was approximately 60%, 76.5%, 100% and 85%, the recovery estimated at the end of reperfusion was 40%, 12%, 70% and 53%, and the resting tension estimated at the end of reperfusion was 2.69+/-0.18 g, 6.40+/-0.50 g, 1.20+/-0.10 g and 1.90+/-0.10 g for cobalt, nickel, manganese and barium, respectively. On the contrary, strontium exerted no protective effects. The protective effects were also indicated by reduced total protein and lactate dehydrogenase activity release into the effluent perfusate and maintenance of electrical activity. The effectiveness of the added divalent cations (with the exception of strontium) showed a strong dependence upon their ionic radius. The most potent inhibitors of this phenomenon in the pigeon heart were the divalent cations having an ionic radius closer to the ionic radius of calcium. These results are discussed in terms of the possible mechanisms involved in the protective effects of these cations.

We studied the blood flow over dorsal and abdominal, non-brooding patch skin of two groups of pigeons: one group was thermally acclimated to cold (winter-acclimatized, WAC) while the other group was acclimated to a mesic environment (thermally non-challenged, NOC). Two bilateral patches at the measurement sites were treated simultaneously with a gel containing sodium nitrate and ascorbic acid, to generate nitric oxide (NO), and a vehicle gel. Blood flow was measured by laser Doppler velocimetry. Changes induced by these treatments were calculated against basic blood flow values for the corresponding patch. The results showed that the basic blood flow over the abdominal skin patches at room temperature was higher than over the dorsal skin in both acclimation states, but comparison revealed a sustainably higher level of basic skin blood flow in the WAC pigeons. The local response to exogenous NO was non-uniform over the two skin areas measured, and a specific vasodilatory action on the abdominal microvessels was recorded in the NOC pigeons. Abdominal vasodilatation in the WAC pigeons seemed to involve other mechanisms as well as local NO-dependent ones, among which the role of cold-induced vasodilatation (CIVD) is discussed here. Interestingly, the dorsal skin seemed to be less responsive to the action of NO, irrespective of the acclimation state. Our results show that acclimation state and skin site affect the action of exogenous NO on local skin blood flow, and we suggest that the differences reflect acclimation-induced changes in the vascularity of the skin and in its sensitivity to thermal stimuli and that the roles of the abdominal and dorsal skin are different with respect to environmental changes.

In the spinal cord of birds a considerable number of neuronal somata is located outside the gray matter. Some of these neurons form segmental marginal nuclei, which lie at the border of the spinal cord near the dentate ligament. In lumbosacral segments these marginal nuclei form accessory lobes which bulge into the vertebral canal. These lobes consist in neurons which are embedded into glia-derived glycogen cells. Furthermore, there are neurons in the white matter near the accessory lobes and numerous paragriseal cells lying in the lateral and ventral funiculus. Glycogen cells are present both in the lobes and in the glycogen body which fills the lumbosacral spinal rhomboid sinus. Immunoreactivity of glial fibrillary acidic protein, a marker of astrocytes, was used to characterize the surrounding of marginal neurons. Astrocytes were numerous in cervical marginal nuclei but rare in accessory lobes. There is cytological (distribution of Nissl substance) and immunocytochemical evidence (immunoreactivity of medium-sized neurofilament, glutamic acid decorboxylase and glutamatergic AMPA receptor subtype GluR2/3) that neurons of the accessory lobes and the nearby white matter are similar, whereas paragriseal cells are different.

Although gamma-aminobutyric acid (GABA) and glutamate are known to be present in the vestibular sensory epithelia of a variety of species, the functional relationship between these two transmitters is not clear. The present study addresses the three-dimensional spatial distribution of GABA and glutamate immunoreactivity in the vestibular labyrinth of the oyster toadfish by using whole end organs labeled by immunofluorescence with monoclonal anti-GABA and/or antiglutamate antibodies and visualized as whole mounts by multiphoton confocal microscopy. We find glutamate-immunoreactive hair cells present throughout the sensory epithelium. In contrast, prominent GABA immunoreactivity is restricted to a small population of hair cells located in the central region of the crista. Double immunofluorescence reveals two distinct staining patterns in GABA-labeled hair cells. Most ( approximately 80%) GABA-labeled cells show trace levels of glutamate, appropriate for the metabolic/synthetic role of cytoplasmic glutamate. The remainder of the GABA-stained cells contain substantial levels of both GABA and glutamate, suggesting transmitter colocalization. In the toadfish utricle, glutamatergic hair cells are present throughout the macula. GABA-immunoreactive hair cells follow the arc of the striola, and most GABA-labeled receptor cells coexpress glutamate. The localization of GABA was explored in other species as well. In the pigeon, GABAergic hair cells are present throughout the crista ampullaris. Our findings demonstrate that multiple, neurochemically distinct types of hair cells are present in vestibular sensory epithelia. These observations, together with the excitatory activity generally associated with 8th nerve afferent fibers, strongly suggest that GABA serves an important, specific, and complex role in determining primary afferent response dynamics., (Copyright 2004 Wiley-Liss, Inc.)

While brain development during embryogenesis has been extensively studied in precocial birds, there is no information available on altricial birds. Thus, the concentrations of the catecholamines norepinephrine (NE), epinephrine (E), and dopamine (DA), and the dopaminergic metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and 4-hydroxy-3-methoxyphenylacetic acid (HVA) were determined at several stages during the late embryonic period (E13, E14, E15, E16, E17 and E18) and the day-of-hatch (P0) in the pigeon telencephalon, cerebellum, optic lobe, and brainstem. The concentrations of all catecholamines were higher than those reported in chicken embryos. During embryogenesis, NE, E, DOPAC and HVA concentrations in the various brain parts increased throughout embryonic development until shortly before hatching at which time they decreased. DA, however, continued to increase through hatching in the brainstem, and the changes in DA concentrations varied in several brain parts. In conclusion, catecholamine concentrations in the various brain parts tended to increase with embryonic age, and the concentrations were higher than those in chickens. Furthermore, brain catcholamine metabolism changed at hatch in pigeons.

The metabolic physiology of the Crested Pigeon (Ocyphaps lophotes) and the Brush Bronzewing (Phaps elegans) is generally similar to that expected for birds of their size, but the Crested Pigeon has a number of characteristics which would aid survival in hot and dry regions. Body temperature increased similarly for the Crested Pigeon (from 38.8 degrees C to 41.5 degrees C) and the Brush Bronzewing (39.3 degrees C to 41.4 degrees C) over ambient temperatures (T(a)s) from 10 degrees C to 35 degrees C. Both species became hyperthermic (body temperature, T(b)>42 degrees C) at T(a)=45 degrees C. Basal metabolic rate of the Crested Pigeon (0.65 ml O(2) g(-1) h(-1) at 40 degrees C) was approximately 71% of that predicted for a columbid bird, while BMR of the Brush Bronzewing (0.87 ml O(2) g(-1) h(-1) at 20 degrees C to 40 degrees C) was approximately 102% of predicted. Total evaporative water loss increased exponentially with T(a) for both species, from <1 mg H(2)O g(-1) h(-1) at 10 degrees C to >12 mg H(2)O g(-1) h(-1) at 45 degrees C. It was similar and low for both species at T(a)<30 degrees C, but was higher for the Brush Bronzewing than the Crested Pigeon at T(a)>30 degrees C. Ventilatory minute volume matched oxygen consumption, such that oxygen extraction efficiency did not change with T(a) and was similar for both species (approximately 20%). Expired air temperature was considerably lower than T(b) for both species at T(a)<35 degrees C, potentially reducing respiratory water loss by approximately 65% at T(a)=10 degrees C to approximately 30% at T(a)=35 degrees C. Cutaneous evaporative cooling was significant for both species, with skin resistance decreasing as T(a) increased. The Crested Pigeon had a lower skin resistance than the Brush Bronzewing at T(a)=45 degrees C. The Brush Bronzewing had apparently reached its maximum cutaneous water loss at 30 degrees C and relied on panting to cool at higher T(a).

Pigeons were allowed to feed for 1 h either 2 h after lights on (morning pulse) or 3 h before lights off (evening pulse). Body temperature was measured radiotelemetrically. Faecal excretion, as an index of rate of digestion, was measured using load cells. At 22 degrees C, faecal excretion peaked just after lights-on in morning-pulse condition, but not in evening-pulse condition. In the cold (+5 degrees C), the peak was absent. We conclude that at thermoneutrality, pigeons are able to postpone a major part of digestion until late in the dark phase when their body temperature is increasing to the diurnal level. Thus, the extra heat from digestion-related thermogenesis that otherwise would be dissipated into the environment can be used for rewarming. In the cold, such a delay is not necessarily advantageous as the extra heat can always be used to substitute for thermoregulatory thermogenesis. The occurrence of concentrated period of digestion only in the morning-pulse condition was correlated to a lower food intake and lower body temperature as compared with the evening-pulse condition. Restricted feeding may thus be needed to induce adaptive timing of digestion as a mechanism of energy sparing. In addition to storage of food, timing of digestion may be a significant factor in the evolution of the crop in birds.

To study the uricolytic properties of urate oxidase in granivorous and carnivorous birds, experiments were conducted in pigeons (Columba livia domestica) and Red-tailed Hawks (Buteo jamaicensis). Plasma concentrations of allantoin and uric acid were determined at various times in experimental groups before and after receiving 100, 200, and 600 U/kg urate oxidase once daily and were compared with controls. All regimens caused a significant decrease in plasma uric acid concentrations within 2 days after the first administration, when compared with controls. Furthermore, both doses used in Red-tailed Hawks (200 and 100 U/kg) caused a significant postprandial suppression of plasma uric acid concentrations. Plasma allantoin concentrations were significantly higher when compared with controls. The ability of urate oxidase to prevent the physiological postprandial hyperuricaemia in Red-tailed Hawks and to reduce plasma uric acid concentrations to undetectable levels, shows the great potential of this drug for treating avian hyperuricaemia.

The distribution of AMPA-type glutamate receptor (GluR) subunits was studied in the Edinger-Westphal nucleus (EW) of chicks and pigeons. GluR1, GluR2, GluR3 and GluR4 subunits appeared to be present in EW neurons of both species, but interspecific differences were observed in the abundance of the different types of subunits found in EW neurons. Of particular note, GluR2 immunoreactivity was present in the vast majority (ca. 80%) of neurons of pigeon EW but was found in only a small fraction (ca. 15%) of chick EW neurons. Scarcity of the GluR2 subunit in chick EW was confirmed by in situ hybridization. Because of the tendency for parvalbumin to be localized to neurons that are selectively deficient in GluR2, we also studied the localization of parvalbumin, as well as other calcium-binding proteins, in EW of chick and pigeon. Parvalbumin was found in more than 50% of chick EW neurons but was not detected in pigeon EW neurons. Our results suggest that there are major glutamatergic inputs to EW neurons in both pigeons and chicks. Furthermore, there are likely to be more AMPA-type calcium-permeable glutamate receptors in EW neurons of chick than in pigeon, since it is known that the subtype containing the edited GluR2 subunit is not calcium permeable.

The effects of local injections of adrenaline into the paraventricular nucleus (PVN) and into other anterior hypothalamic areas on blood glucose levels were investigated in conscious pigeons (Columba livia). Adrenaline evoked a reliable and potent increase in blood glucose levels when injected into the PVN; no glycemic change was observed after vehicle injections into the PVN or after adrenaline injections into the 3rd ventricle or hypothalamic structures adjacent to the PVN. Local pretreatment with propranolol, but not with phentolamine, abolished the adrenaline-induced hyperglycemia. The present results indicate that adrenergically mediated circuits into the avian PVN play an important role in central mechanisms of energy balance that may be equivalent to those observed in mammalian species.

Dopamine (DA) in mammalian associative structures, such as the prefrontal cortex (PFC), plays a prominent role in learning and memory processes, and its homeostasis differs from that of DA in the striatum, a sensorimotor region. The neostriatum caudolaterale (NCL) of birds resembles the mammalian PFC according to connectional, electrophysiological, and behavioral data. In the present study, DA regulation in the associative NCL and the striatal lobus parolfactorius (LPO) of pigeons was compared to uncover possible differences corresponding to those between mammalian PFC and striatum. Extracellular levels of DA and its metabolites (homovanillic acid [HVA], dihydroxyphenylacetic acid [DOPAC]) and the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) were investigated by in vivo microdialysis of urethane-anesthetized pigeons under basal conditions and after systemic administration of D-amphetamine. DA was reliably determined only in LPO dialysates, and DA metabolite levels were significantly higher in LPO than in NCL. The HVA/DOPAC ratio, indicating extracellular lifetime of DA, was more than twice as high in NCL than in LPO dialysates. After amphetamine, DA increased in LPO while still being undetectable in NCL, and DA metabolites decreased in both regions. 5-HIAA slightly decreased in NCL dialysates. Amphetamine effects were delayed in NCL compared with the striatum. In conclusion, effects of amphetamine on the pigeon's ascending monoamine systems resemble those found in mammals, suggesting similar regulatory properties. The neurochemical differences between NCL and LPO parallel those between associative regions, such as PFC and dorsal striatum in mammals. They may reflect weaker regulation of extracellular DA, favoring DAergic volume transmission, in associative than striatal forebrain regions., (Copyright 2002 Wiley-Liss, Inc.)

The effects of intracerebroventricular pretreatment with muscarinic (scopolamine or methylscopolamine; 2.7 nmol or 5.4 nmol) or nicotinic (mecamylamine, 2.7 nmol or 5.4 nmol) cholinergic receptor antagonists on plasma free fatty acid increases induced by intracerebroventricular injections of carbachol in conscious resting pigeons (Columba livia) were examined. Plasma glucose levels were also measured throughout the experiments. Pretreatment with methylscopolamine suppressed the lipolytic effect of carbachol injections, while mecamylamine left this response unchanged. Neither carbachol treatment alone, nor the pretreatments with cholinergic agents affected glucose levels. Subsequently, the effects of intracerebroventricular injections of methylscopolamine were investigated in 24-h food-deprived pigeons. The increase in free fatty acid levels after fasting was of a magnitude similar to that observed after carbachol treatment; intracerebroventricular injections of methylscopolamine (5.4 nmol) transiently but powerfully decreased plasma free fatty acids in 24-h food-deprived pigeons to levels comparable to those of free-feeding animals. The fasting-induced decrease in glucose levels was not affected by this treatment. These data indicate that the lipolytic response induced by carbachol may be mediated by central muscarinic cholinergic receptors and that this central cholinergic mechanism partially contributes to plasma free fatty acid increases observed during fasting. Furthermore, the absence of effects on glucose levels suggests that these cholinergic mechanisms participate selectively in the lipolytic component of the metabolic response to fasting.

The ultrastructural features of serotonergic fibers, terminals and synaptic contacts were studied with the pre-embedding immunocytochemical method in the isthmo-optic nucleus of the pigeon centrifugal visual system. The 5-HT immunoreactive (-ir) profiles were diffusely distributed and their density was low. The labeled axons were thin and unmyelinated (mean diameter=0.21+/-0.03 microm) though a few larger myelinated axons were observed (mean diameter=0.51+/-0.07 microm). The 5-HT-ir terminals or varicosities were small (diameter=0.71+/-0.54 microm) and contained small agranular synaptic vesicles (diameter=28.5+/-6.9 nm) and large granular vesicles (diameter=102.2+/-19.5 nm). The latter only constituted approximately 1% of the total profiles containing synaptic vesicles in the isthmo-optic nucleus. In single thin sections, only 5% of the 5-HT-ir varicosities exhibited an active asymmetrical zone synapsing upon dendritic profiles of centrifugal visual neurons. Calculations indicated that 17% of these 5-HT-ir varicosities were actually engaged in junctional synaptic relationships, whereas the remaining (83%) were nonjunctional. The data suggest that, within the isthmo-optic nucleus, 5-HT acts both at synaptic junctions (wiring transmission) and at a distance via the extracellular space (volume transmission). These 5-HT afferents could thus modulate the activity of the retinopetal neurons and visual information processing.

Earlier morphological studies of the epithelial structure in the semicircular canals of mammals have focused on the sensory cells of the crista ampullaris. This report draws attention to the fact that there exist at least seven further cell types in the horizontal ampulla walls of pigeon with various functions; the role of ion- and H2O-transporting epithelial cells is dealt with here in detail. While the dark cells appear to play a decisive role in the regulation of ionic composition, the cells in the planum semilunatum may transport H2O and assist in the regulation of endolymph volume. In addition, protein-secreting structures are located in the apical region of the cells of the planum semilunatum. The question whether the proteins are dispersed in the endolymph or contribute to cupula formation remains unclear. The morphology and possible functions of these two cell types are discussed on the basis of electron microscopic results.

In birds there are segmentally organized marginal nuclei at the lateral or ventrolateral border of the spinal cord. In most regions of the spinal cord these nuclei are within the outline of the cord. However, in the lumbosacral region they form accessory lobes protruding into the vertebral canal. Histochemical and immunocytochemical investigations were performed to study the neurochemical features of the marginal nuclei of the pigeon. Despite histological differences (only accessory lobe neurons are embedded in glia-derived glycogen cells), there was no difference in the chemical neuroanatomy of the two types of marginal nuclei. These nuclei contained cholinergic neurons and there was also evidence for a cholinergic innervation. NADPH-diaphorase activity, which is considered to indicate nitric oxide synthesis, was faint in marginal neurons. No serotonin immunoreactivity was found. However, all neurons showed immunoreactivity to glutamate and glycine, and some were immunoreactive to gamma-aminobutyric acid (GABA). A GABAergic innervation of non-GABAergic neurons could also be demonstrated. The lack of difference in the chemical neuroanatomical features between cervical marginal nuclei and lumbosacral accessory lobes suggests a similar origin of all marginal neurons. A comparison with the chemical neuroanatomy of marginal neurons in other vertebrates shows both similarities and differences.

Whether the endolymph of the semicircular canal passes the cupular partition or not was examined using the lateral semicircular canal system of adult pigeons (Columba livia). By applying various pressures by means of injection of a dye solution through the membranous canal, it was found that the dye solution, was seen to pass the cupula even under very low pressures when the pressure was increased gradually. When pulled by a magnet, the ultrafine particles of the dextran magnetite contained in the injected fluid were found to pass through the subcupular space without evident increase of the ampullary pressure., (c 2001. Elsevier Science Ltd. All rights reserved.)

The avian isthmic nuclei are constituted by a group of structures reciprocally connected with the tectum opticum and considered to play a role in the modulation of intratectal processes. Although the two larger isthmic nuclei, the n. isthmi pars parvocellularis (Ipc) and the n. isthmi pars magnocellularis (Imc), have been studied in detail previously, the third and smallest of this group, the n. isthmi pars semilunaris (SLu), has been largely neglected. The present study demonstrates this isthmic component to be characterized by a unique connectivity and immunohistochemical pattern: 1) SLu receives tectal afferents and projects back onto the outer retinorecipient tectal layers; 2) it projects bilaterally onto the nucleus rotundus and thus modulates the ascending tectofugal system; 3) in addition, previous studies have demonstrated SLu projections onto the lateral spiriform nucleus (SpL), which mediates basal ganglia output onto the tectum. In that SpL projects onto the deep layers of the tectum, SLu indirectly modulates descending tectal output patterns. Taken together, the role of SLu goes far beyond a local modulation of intratectal processes. Instead, this isthmic structure is likely to play a key role in the topographically organized modulation of the ascending and, at least indirectly, also the descending projections of the optic tectum., (Copyright 2001 Wiley-Liss, Inc.)

The distribution of the neurotrophins BDNF and NT-3 as well as their corresponding high-affinity receptors trkB and trkC was characterized by immunohistochemistry in the developing retino-tectal system of the pigeon. These neurotrophins are known to be important for survival and development of neuronal tissues, but also for activity-dependent neuronal plasticity. In pigeons visual asymmetry is established at the morphological and behavioral level due to a natural asymmetrical light input before hatch, which is followed by a posthatch period of consolidation with unbiased light stimulation. Since the retino-tectal system is the crucial entity of these events, we studied the retinal and the tectal distribution of these neurotrophins and their receptors during retino-tectal formation, to analyze the developmental sequences to which these neurotrophins are tuned. Here we demonstrate that in altricial pigeons no retinal immunolabeling of BDNF, NT-3 or their receptors could be detected before hatch, although a prominent tectal labeling pattern throughout most layers was evident. After hatch, both neurotrophins and their receptors showed a dramatic increase of retinal and tectal distribution. While the tectal and retinal protein synthesis of NT-3 vanished after 2 weeks, that of BDNF could still be revealed in adults. Therefore, the establishment of the retino-tectal system does not seem to depend on these neurotrophins before hatch, although they are probably utilized to shape the intratectal wiring pattern. In contrast, BDNF and NT-3 could play a prominent role in posthatch retino-tectal plasticity, as the consolidation of tectal asymmetries requires posthatch modifications of tectal circuits and proceeds within the first two posthatching weeks. These data are comparable with the distribution of neurotrophins in the retino-tectal system of chicks, although the onset of neurotrophin synthesis seems to be earlier in precocial chicks.

Although neuropeptide-Y (NPY) has been widely reported to be a potent stimulator of feeding activity and regulator of energy homeostasis, most of the supportive evidence for such effects has been gathered in mammalian species. This study characterized the orexigenic potency of NPY in an avian species, the ring dove, and measured changes in hypothalamic NPY-immunoreactive (NPY-ir) cell numbers in response to energy state fluctuations or intracranial administration of the potent orexigenic hormone prolactin. Food intake was significantly elevated in male doves at 1 h after intracerebroventricular (i.c.v.) injection of 0.25 and 0.5 microg NPY but not after injection of a higher dose (1.0 microg). In time course studies, food intake was increased at 1 h after i.c.v. injection of 0.5 microg NPY but was not elevated at 2, 3, or 4 h. The number of NPY-ir cell bodies in the infundibular region of the dove hypothalamus increased two to four-fold following acute food deprivation, chronic food restriction, or repeated i.c.v. injections of prolactin. No additive effects were observed when food restriction and prolactin treatment were combined. These findings suggest that NPY is involved in energy homeostasis in doves and are consistent with the hypothesis that prolactin-induced hyperphagia is mediated in part by NPY.

The influence of maternal versus dietary sources of polychlorinated biphenyls (PCBs) deposited to eggs of ring doves (Streptopelia risoria) was investigated. Mature birds that lay a clutch of two eggs every 12 to 15 d were fed a diet of pellets spiked with 2,2',4,4',5,5'-hexacholorobiphenyl (unlabelled isotope designated as [12C]PCB153) for 25 d. The birds were subsequently switched to a diet containing isotopically labeled [U-13C12]PCB153 at similar concentrations for an additional 63 d. The toxicokinetics of [12C]PCB153 and [13C]PCB153 were followed in egg and carcass samples with time. Isotopic ratios of PCB153 in yolk lipids were identical to those in carcass lipids after introduction of diet 2, and they did not resemble those of the food at the time of egg formation. The data indicate that the PCB composition of eggs directly reflects the composition of maternal tissues, not the diet, at the time of yolk formation. Egg yolk:carcass lipid concentration ratios for the two isotopes were significantly less than one, averaging 0.33+/-0.02 (mean +/- standard error). Lipid normalized egg:maternal tissue contaminant concentration ratios for persistent organochlorine chemicals in the literature were reviewed for other avian species. The results provide a preliminary data set that suggests egg:maternal tissue contaminant concentration ratios vary among species, particularly among species that invest different quantities of lipids to a clutch of eggs. The results support the hypothesis that dilution of contaminants in egg lipids relative to maternal lipids is related to the reproductive strategy employed by the species.