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Background: The rat has served usefully as a model for fecal incontinence and exploration of the mechanism of action of sacral neuromodulation. However, there is a gap in knowledge concerning representation(s) on the primary sensory cortex of this anatomical region., Methods: Multi-electrode array (32 channels) and intrinsic optical signal (IOS) processing were used to map cortical activation sites following anorectal electrical stimulation in the rat. A simple method for expanding a 32-electrode array to a virtual 2700 array was refined., Key Results: The IOS method identified activation of parietal cortex following anorectal or first sacral nerve root (S1) stimulation; however, the signal was poorly localized and large spontaneous vasomotion was observed in pial vessels. In contrast, the resulting high-density maps showed two anatomically distinct cortical activation sites to anorectal stimulation., Conclusions & Inferences: There are two distinct sites of activation on the parietal cortex following anorectal stimulation in the rat. The implications for sacral neuromodulation as a therapy for fecal incontinence are discussed., (© 2019 John Wiley & Sons Ltd.)

Zinc release in the lateral nucleus of the amygdala was examined using rat brain slices. The lateral and basolateral nuclei in the amygdala were evidently stained by Timm's sulfide-silver staining method. When the amygdala including both the nuclei was stimulated with 100 mM KCl by means of in vivo microdialysis, extracellular zinc concentration was increased significantly. Zinc release in the lateral nucleus of the amygdala innervated by the entorhinal cortex was next examined in brain slices double-stained with zinc and calcium indicators. Extracellular zinc signal (ZnAF-2) in the lateral nucleus was increased with intracellular calcium signal (calcium orange) during delivery of tetanic stimuli to the entorhinal cortex. Both the increases were completely inhibited by addition of 1 micro M tetrodotoxin, a sodium channel blocker. Furthermore, calcium signal in the lateral nucleus during delivery of tetanic stimuli to the entorhinal cortex was increased in the presence of 10 micro M CNQX, an AMPA/KA receptor antagonist, and this increase was facilitated by addition of 1 mM CaEDTA, a membrane-impermeable zinc chelator. The present study suggested that zinc is released in the lateral nucleus of the amygdala by depolarization of the entorhinal neurons. In the lateral nucleus, zinc released may suppress the increase in presynaptic calcium signal.

Despite being one of the more extensively investigated descending pathways of the rat spinal cord, the termination pattern and postsynaptic targets of the rubrospinal tract (RST) still present some unresolved issues. In addition to locomotor functions, the RST is implicated in the control of limb movements such as reaching and grasping. Although a strong RST projection onto interneurons of intermediate Rexed's laminae V and VI have been described through the entire length of the rat spinal cord, the existence of direct rubro-motoneuronal connections have not been demonstrated. In the present study, anterograde tracing of the rat RST with biotinylated dextran amine (BDA) was combined with injections of cholera toxin beta-subunit (CTbeta) into selected groups of forelimb muscles to analyze in detail the rubral projections to the forelimb areas of the cervical spinal cord. The double-staining procedure suggested a direct projection from the RST to specific populations of motoneurons. Three populations of forelimb muscles were distinguished, i.e., paw, "distal" muscles; forearm, "intermediate" muscles; and upper arm, "proximal" muscles. A somatotopic distribution of the corresponding motor neuron pools was present in the spinal cord segments C4-Th1. Rubrospinal axons were seen in close apposition to the distal and intermediate muscle motoneurons, but were consistently absent in the most ventrally situated motor column projecting to proximal muscles. Microstimulation of the red nucleus resulted in electromyographic responses with shorter latency in the distal forelimb muscles than in proximal muscles. These experiments support a specific, preferential role of the RST in distal forelimb muscle control., (Copyright 2002 Wiley-Liss, Inc.)

The object of this study was to analyze the synaptic interactions of identified muscle spindle afferent axon terminals in the spinal cord of the rat. Group 1a muscle afferents supplying the gastrocnemius muscle were impaled with microelectrodes in the dorsal white matter of the spinal cord and stained by intracellular injection with Neurobiotin. Postembedding immunogold techniques were used to reveal GABA- and glycine-like immunoreactivity in boutons presynaptic to afferent terminals in the ventral horn and the deep layers of the dorsal horn. Serial-section reconstruction was used to reveal the distribution of synaptic contacts of different types on the afferent terminals. The majority of afferent boutons received axoaxonic and made axodendritic or axosomatic synaptic contacts. In the ventral horn, 91% of boutons presynaptic to the afferent terminals were immunoreactive for GABA alone and 9% were immunoreactive for both GABA and glycine. The mean number of axo-axonic contacts received per terminal was 2.7, and the mean number of synaptic contacts at which the terminal was the presynaptic element was 1.4. In the deep layers of the dorsal horn, 58% of boutons presynaptic to afferent terminals were immunoreactive for GABA alone, 31% were immunoreactive for GABA and glycine, and 11% for glycine alone. The mean number of axoaxonic contacts received per afferent terminal in this region was 1.6 and the mean number of synaptic contacts at which the terminal was the presynaptic element was 0.86. This clearly establishes the principle that activity in 1a afferents is modulated by several neurochemically distinct populations of presynaptic neuron., (Copyright 2001 Wiley-Liss, Inc.)

Protein extravasation and vasodilatation can be induced by neuropeptides released from nociceptive afferents (neurogenic inflammation). We measured electrically evoked neuropeptide release and concomitant protein extravasation in human and rat skin using intradermal microdialysis. Plasmapheresis capillaries were inserted intradermally at a length of 1.5 cm in the volar forearm of human subjects or abdominal skin of rats. Capillaries were perfused with Ringer solution at a flow rate of 2.5 or 1.6 microl min(-1). After a baseline period of 60 min capillaries were stimulated electrically (1 Hz, 80 mA, 0.5 ms or 4 Hz, 30 mA, 0.5 ms) for 30 min using a surface electrode directly above the capillaries and a stainless-steel wire inserted in the capillaries. Total protein concentration was assessed photometrically and calcitonin gene-related peptide (CGRP) and substance P (SP) concentrations were measured by enzyme-linked immunosorbent assay (ELISA). In rat skin, electrical stimulation increased CGRP and total protein concentration in the dialysate. SP measurements showed a larger variance but only for the 1 Hz stimulation was the increased release significant. In human skin, electrical stimulation provoked a large flare reaction and at a frequency of 4 Hz both CGRP and SP concentrations increased significantly. In spite of the large flare reactions no protein extravasation was induced, which suggests major species differences. It will be of interest to investigate whether the lack of neurogenic protein extravasation is also valid under pathophysiological conditions.

A specific colony of Wistar rats was found in which the common carotid artery bifurcates at an unusually caudal position, thereby the carotid sinus nerve that originates from the bifurcation is elongated. The present study was done to determine whether this elongated nerve carries baro- and chemosensations in the same manner as the carotid sinus nerve of conventional rats or of other species. In chloralose-urethane anesthetized rats of this specific colony, the afferent discharges were recorded from the elongated carotid sinus nerve in response to a phenylephrine-induced rise in blood pressure and a fall in oxygen tension, as well as an increase in carbon dioxide tension in the respiratory gas. Reflex effects of electrical stimulation of the nerve were also examined. In nerve recording, the afferent discharges of the elongated carotid sinus nerve were increased by any of the perturbations, hypertensive, hypoxic or hypercapnic. Electrical stimulation of the elongated carotid sinus nerve caused an initial rise and a subsequent fall in blood pressure, bradycardia, and an increase of respiratory volume and rate. These results confirmed that the elongated carotid sinus nerve of rats in this colony contains both baroreceptor and chemoreceptor afferent fibers. It seems that this colony of rats proffers a beneficial material which will facilitate the studies to analyze the features and reflex functions of carotid body chemoreceptors and/or carotid sinus baroreceptors.

During the brain maturation a critical period is detectable when the sensitivity of the neocortex is high. Enhanced excitatory activity is characteristic at that time while the inhibitory processes are underdeveloped. The goal of this study was to determine the effectiveness of different types of excitatory amino acid antagonists reducing the electrically evoked excitatory synaptic responses of the somatosensory cortex. Effects of the specific competitive N-methyl-D-aspartate (NMDA) antagonist 4-amino-phosphono-valerate (APV), and the specific non-competitive, non-NMDA antagonist 1-(4-aminophenyl)-3-methylcarbamoyl-7,8-methylenedioxy-5H-2,3-benz odiazepine (GYKI 53655) were analysed on neocortex slices prepared from 2-week-old and adult rats. APV caused a partial inhibition of the electrically evoked response more effectively in young animals than in adults, while the effective IC50 values were similar. In contrast, the non-NMDA antagonist had a similar effect on the slices of both age-groups.

Since the 10-Hz rhythmic activity in the sympathetic nerves was reported only in cats, we examined whether the activity of the same frequency could be observed in rats and rabbits as well as in the cats. Histograms of inter-burst-peak intervals of discharges of the renal nerves revealed that the 100 ms interval activity, the reverse of the 10-Hz, was observed in all the three mammals, of which the baroreceptor afferents were intact or inactivated. Further, the same frequency activity could be evoked by intermittent electrical stimulation of the dorsolateral funiculus of the cervical cord in spinal animals. It was suggested that the 10-Hz rhythmic activity in the sympathetic nerves was a common phenomenon throughout mammals and this activity was produced in the spinal cord. The physiological significance of the 10-Hz activity in the sympathetic nerves was discussed.

Many peripherally administered substances which modulate memory do not freely enter the brain. Such compounds may act through peripheral receptors that send messages centrally through vagal afferents. To explore this hypothesis, rats were chronically implanted with cuff electrodes on the left cervical vagus nerve. Each animal was trained 48 h after surgery on a one-trial inhibitory-avoidance task with a 0.75-mA, 1.0-s footshock. Immediately following training, each animal received either no stimulation or vagal stimulation (0.5-ms biphasic pulses; 20 Hz, 30 s) at one of three intensities (0.2, 0.4, 0.8 mA; eight animals per group). Retention was tested 24 h later. Neither the 0.2-in or 0.8-mA groups (22.1-s; 53.7-s median latency) showed altered retention performances, whereas the 0.4-mA group showed significantly improved retention (881.0 s) compared to unstimulated controls (21.1 s; U = 6, p < .01). This inverted-U shaped function indicates that vagal activation during memory consolidation modulates retention for memory tasks.

Rats learned serial patterns composed of either "run" chunks (e.g., 123 234 ...) or "trill" chunks (e.g., 121 232 ...). For each type of pattern, 1 group of rats encountered an element at the end of the pattern that violated the run or trill structure. In both run and trill patterns, violations were unusually difficult for rats to learn, whereas corresponding elements in "perfect" patterns that did not violate pattern structure were easy. Additionally, rats' errors on violation elements conformed to the structure of the patterns in which they were embedded. Thus, rats were sensitive to the run or trill organization of their patterns and mastered the rules governing the pattern before learning "exceptions to the rule."

A complete understanding of the neural mechanisms responsible for the chemoreceptor and baroreceptor reflexes requires precise knowledge of the locations and chemical phenotypes of higher-order neurons within these reflex pathways. In the present study, the protein product (Fos) of the c-fos protooncogene was used as a metabolic marker to trace central neural pathways following activation of carotid sinus nerve afferent fibers. In addition, immunohistochemical double-labeling techniques were used to define the chemical phenotypes of activated neurons. Both electrical stimulation of the carotid sinus nerve and physiological stimulation of the carotid bodies by hypoxia induced Fos-like immunoreactivity in catecholaminergic neurons containing tyrosine hydroxylase or phenylethanolamine-N-methyltransferase in the ventrolateral medulla oblongata and, to a lesser degree, in the dorsal vagal complex. Tyrosine hydroxylase/Fos colocalization was also observed in the locus coeruleus and the A5 noradrenergic cell group in pons. Many serotoninergic neurons in nucleus raphe pallidus, nucleus raphe magnus, and along the ventral medullary surface contained Fos-like immunoreactivity. In pons and midbrain, Fos-like immunoreactivity was observed in the lateral parabrachial and Kölliker-Fuse nuclei, the inferior colliculus, the cuneiform nucleus, and in the vicinity of the Edinger-Westphal nucleus, but no catecholaminergic or serotoninergic colocalization was observed in these regions. Although Fos-labeled cells were observed within and lateral to the dorsal raphe nucleus, few were catecholaminergic or serotoninergic. This study further defines a potential central neuroanatomical substrate for the chemoreceptor and/or baroreceptor reflexes.

The efferent connections of the hypothalamic area of the rat, where attack behaviour can be elicited by electrical stimulation, were studied using iontophoretic injections of Phaseolus vulgaris-leucoagglutinin. Specificity for the hypothalamic "attack area" was investigated by comparison with efferents of hypothalamic sites outside the attack area. The hypothalamic attack area consists of the intermediate hypothalamic area and the ventrolateral pole of the ventromedial hypothalamic nucleus. Fibres from the hypothalamic attack area, as well as fibres from several other hypothalamic sites, form diffuse fibre "streams" running rostrally or caudally. Many varicosities that are found on the fibres suggest, that these fibres are capable of influencing many brain sites along their way. Projection sites were found throughout the brain. In the comparison between attack area efferents and controls, many overlapping brain sites were found. Hypothalamic efferents preferentially originating in the largest part of the attack area, i.e. the intermediate hypothalamic area, were found in the mediodorsal and parataenial thalamic nuclei. Within the septum, a spatial organization of hypothalamic innervation was found. Fibres from the attack area formed specialized "pericellular baskets" in the dorsolateral aspect of the intermediate part of the lateral septal nucleus. Fibres from other hypothalamic sites were found in other septal areas and did not form these septal baskets. Within the mesencephalic central gray, fibres from the attack area were found specifically in the dorsal part and dorsal aspect of the lateral part of the central gray. Physiological and pharmacological studies have shown that several brain sites are involved in different aspects of aggressive behaviour. Some of these areas, as for instance the dorsomedial thalamic nucleus, septum and central gray, are innervated by efferents from the hypothalamic attack area, whereas other sites, like ventral premammillary nucleus and ventral tegmental area, are not. It is concluded from the present findings, that a number of brain sites, that are known to be involved in agonistic behaviour, receive hypothalamic information preferentially from the hypothalamic attack area through diffusely arranged varicose fibres. The function of each connection in the regulation of specific behaviours remains to be further investigated.

Physiological evidence is presented for the existence of commissural fibres that cross the midsagittal plane in the medulla of the rat at the level of the trigeminal motor nucleus (Mo5). These fibres, which have their origin in the Mo5, terminated in the contralateral Mo5. Small inhibitory postsynaptic potentials were recorded in jaw-closing motoneurones by electrical activation of the commissural fibres; jaw-opening and fusimotor neurones as well as the jaw-closing and jaw-opening reflex were not affected. Electromyographic recordings from jaw-closing and jaw-opening muscles in the unrestrained rat showed that masseter activity was inhibited by the commissural fibres. These trigeminal commissural connections might play a part in the co-ordination of bilateral activity of the jaw-closing musculature during unilateral chewing.

In this study, twenty four albino rats, weighing between 180 and 200 g were tested. One half was fed with a diet containing 1% cholesterol for 12 weeks and the other half was fed with a normal lab diet for the same period. After the experimental period, the plasma cholesterol level in the diet group was 134.04 +/- 21.11 mg/dl compared with the control group 72.72 +/- 10.5 mg/dl. In the two groups, SEPs were recorded from central (Cz) referenced to frontal (Fz) following left posterior tibial nerve (PTN) stimulation. Amplitude spectra of SEPs were computed by Fast Fourier Transform (FFT) algorithm. Their amplitude maxima were found to occupy the frequency bands of 1-3.5, 4-5, 6-7, 8-10, 11-12, 13-20, 20.5-36 and 36 Hz and above. The decibel (dB) values of the maxima were statistically lower for hypercholesterolemia than for the normals in the all the frequency bands.

The cerebral response evoked by stimulation of the bulbar pyramidal tract in wood rats, like that of laboratory rats, consisted of a small alpha wave, almost obscured by a very large, superimposed r wave. The alpha wave behaved like a purely antidromic response, whereas the r wave behaved like a postsynaptic response, including a marked variability in amplitude on repeated trials. The contralateral forepaw and hindpaw motor sites mapped onto the somatic sensory foci for these two paws; further examination showed that the somatic sensory and motor representations were largely superimposed. An incipient sagittal fissure 1.5 mm lateral to the midline marked the boundary between limbic and neocortex. Because of their structural similarities and their differences in somatic sensory and motor organization, wood rats and laboratory rats are prime subjects for comparative study of the role of amalgamated and separate sensory and motor cortices in regulating movement and behavior.

Supravital excitability to electrical stimuli (for convenience, supravital electrocontractility (S.Ec) of the gastrocnemius muscle of rats and bullfrogs was examined after "somatic death" and the time during which S.Ec could be detected (S.Ec duration) was measured. S.Ec of the gastrocnemius muscle of rats and bullfrogs depended on temperature. The maximum S.Ec duration of the muscle of rats and bullfrogs were 110 min and 96 hr, respectively, at a low temperature (5 degrees), and 60 min and 9 hr, respectively, at a high temperature (30 degrees). The time course of rigor mortis at 5 degrees was slow and it was rapid at 30 degrees. In rats, the S.Ec disappeared completely before the onset of rigor mortis, and in bullfrogs, S.Ec existed at progressive stages of rigor mortis and it disappeared completely when rigor mortis reached about the maximum.

Fourteen rats with bilaterally implanted lateral hypothalamic electrodes were allowed to self-stimulate each side of the brain during daily test sessions. Rotation (circling behavior) during self-stimulation sessions was also recorded. All rats rotated in preferential direction regardless of the side of the brain stimulated, and, in each case, the direction was the same as that subsequently determined in response to d-amphetamine. All rats had asymmetries in self-stimulation thresholds related to the direction of rotation. Thresholds were lower on the side contralateral to the direction of rotation, and entire rate-intensity functions were displaced to the left on that side. The results, discussed in terms of lateralization of affect, suggest a model in which quantitative differences in neuronal firing can be translated into apparent qualitative specialization, with the two sides of the brain appearing to be specialized for high and low mood, respectively.

The receptive field (RF) of 67 taste and 85 mechanoreceptive neurons in the solitary tract nucleus (NTS) were located in the oral cavity in albino rats. All of the taste and most (62.4%) of the mechanoreceptive neurons examined had an RF on the ipsilateral side of the tongue and/or the palate. Regardless of whether they were solitario-parabrachial relay (SP) neurons or non-SP neurons, RFs of taste neurons were found on the anterior as well as the posterior tongue. But there were some differences in the RF distribution between the SP and non-SP mechanoreceptive neurons. Most of the mechanoreceptive SP neurons (9 of 11) had an RF on the tongue, while ca. half of the mechanoreceptive non-SP neurons (43 of 79) had an RF on the tongue and palate, but the rest had an RF on other tissue. Most of the neurons studied had a small restricted RF, but complex RFs, e.g. two separate RFs on the tongue, were found in a relatively small number of neurons (four taste and five mechanoreceptive neurons). An inhibitory RF, usually in a remote place from the excitatory RFs, was found in four mechanoreceptive neurons but no inhibitory RFs for taste neurons. Electrical stimulation of the epithelium in the RF with a low current of short duration evoked a few spikes in most units. Two of the three units, giving rise to a vigorous response to taste stimulation, but having single restricted RFs on the anterior tongue, produced a train of spikes lasting more than 20 ms in response to electrical stimulation of the RF.(ABSTRACT TRUNCATED AT 250 WORDS)

1 The cat anococcygeus muscle is shown to possess a dual innervation similar to the rat anococcygeus, with a motor adrenergic innervation and an inhibitory innervation whose transmitter is unknown. The pharmacological properties of the cat muscle were investigated and compared with those of the rat muscle.2 The cat muscle contracts to noradrenaline, 5-hydroxytryptamine, tyramine, amphetamine, guanethidine, cocaine and lysergic acid diethylamide (LSD). The effects of noradrenaline and 5-hydroxytryptamine are blocked by phentolamine and methysergide respectively.3 The cat anococcygeus is relaxed by acetylcholine, carbachol, isoprenaline, ATP, prostaglandins E(1), E(2) and F(2alpha) and vasopressin, all of which contract the rat muscle. The effects of acetylcholine and carbachol are blocked by atropine and those of isoprenaline by propranolol.4 Field stimulation produces contraction of the cat anococcygeus, which is blocked by phentolamine and guanethidine but unaffected by hexamethonium, atropine or neostigmine.5 In the presence of guanethidine (10(-5)M), the tone of the muscle is raised and field stimulation produces relaxation of the muscle. These inhibitory responses are unaffected by phentolamine, hexamethonium, atropine or neostigmine.6 Neostigmine potentiates the effects of acetylcholine, but not of carbachol in relaxing the cat anococcygeus and in contracting the rat anococcygeus, but has no effect on either motor or inhibitory responses to field stimulation.7 Cold storage for up to eight days had little effect on either the motor response to noradrenaline or the motor or inhibitory response to field stimulation of the cat anococcygeus. Beyond eight days, the response to field stimulation diminishes more rapidly than the response to noradrenaline.

We have recently identified two functional subdivisions of the nucleus tractus solitarii (NTS) in the cat: the pressor and apneustic (inspiratory) response zone, and the depressor and apneic (hypopneic) response zone. The presence of such functional subdivisions in the NTS of the rat was explored. The circulatory and respiratory responses to electrical stimulation of a small part of the NTS were surveyed in all regions of the NTS in rats anesthetized with urethane (500 mg/kg, i.p.). A set of depressor, bradycardiac and apneic responses was elicited in the dorsomedial portions, whereas a pressor response with or without an apneic (hypopneic) response was elicited in the ventral and lateral portions. The presence of a difference in the functional subdivisions between spontaneously hypertensive rats (SHR) and normotensive rats (WKY) was also explored. The SHR group showed significantly larger pressor responses than the WKY group (P less than 0.001), despite its higher basal level of arterial blood pressure, but significantly fewer bradycardiac responses (P less than 0.001). This suggests the SHR group is more sensitive in terms of sympathetic vasomotor activity but less sensitive in parasympathetic cardioinhibitory activity. There was no significant difference in the distribution of the pressor and depressor response zones between the two strains.

The response patterns of cells in the dorsal lateral geniculate nucleus of the albino rat were studied in order to examine the functional organization of the lateral geniculate nucleus. Both photic stimulation and electrical stimulation of the optic tract were used to activate single units in the lateral geniculate nuclei. Three different types of response patterns were found for principal cells, while interneurons all had similar response patterns. The first class of principal cells, E-S cells, responded to stimulation with a period of excitation, followed by a period when activity was suppressed. A second class of cells, S cells, responded to photic stimulation with an initial period when activity was suppressed. The final class of cells, E cells, responded with a period of excitation followed by a return to spontaneous rates of firing. The response patterns of E cells suggest that this type of principal neuron does not receive feedback inhibition of the type proposed in previous models of the lateral geniculate nuclei. Based on these and other observations, a new model of the functional organization of the lateral geniculate nuclei is proposed.

Lesions in the anterior part of the corticomedial amygdaloid nucleus decreased the frequency of lordotic reponses in ovariectomized rats treated with estradiol benzoate and progesterone. Electrochemical stimulation (iron deposition) of the same area had the opposite effect. When lesions were made in the posterior part of the lateral amygdaloid nucleus a highly significant increase in receptivity was observed; on the other hand stimulation in this region depressed the lordosis quotient in receptive animals. Appropriate controls showed that the effects observed after lesioning cannot be attributed to the different estrogen doses used, nor to nonspecific effects of tissue destruction. Similarly, the changes observed after electrochemical stimulation do not depend on the lesion produced by this procedure or the repeated-tests paradigm employed. Electrocorticograms and electroencephalograms of the amygdala showed no apparent alterations after electrochemical stimulations. It is proposed that amygdaloid structures play a modulatory and integrative role on the control of sexual behavior in the female rat: activation of cells in the anterior part of the corticomedial nucleus increases the probability of lordotic responses while excitation of the neurons in the posterior part of the lateral nucleus has the opposite effect.

The dorsal and ventral vertebral muscles of the back and the tail of the albino Norway rat are described and discussed. These muscles were analyzed because they are undoubtably used during the sexual posturing, lordosis, of the female rat, as well as participating in a variety of other behaviors. The muscles are described by region (thoracic-lumbar or sacrocaudal), and the classifications of Vallois are followed where possible. Of the epaxial (dorsal) muscles, the three longitudinal systems of muscles, the transversospinalis, the longissimus, and the iliocostalis systems, can be identified in the albino rat. Muscles of the transversospinalis system are fused in the lumbar region, distinct and specialized in the thoracic region, and form the tail muscle extensor caudae medialis caudally. The iliocostalis system of the lumbar region is fused with one component of the lumbar longissimus system to form lateral longissimus. Anteriorly, iliocostalis thoracis and cervicis represent the iliocostalis system. The lumbar longissimus system is represented by the longissimus component of lateral longissimus, medial longissimus, and a short-fiber component. Longissimus dorsi is the anterior continuation of the longissimus portion of the lateral longissimus. The short-fiber component also continues into the thoracic region, where it becomes difficult to separate out from longissimus dorsi. Medial longissimus represents the excursion into the lumbar region of the long, tendinous, tailbase-tail muscle, longissimus caudae; the caudal portion of this muscle is extensor caudae lateralis. The remaining dorsal muscle described is the tail muscle, abductor caudae dorsalis. The hyposomal (ventral) muscles described are quadratus lumborum and the intertransversarii, present in the lumbar region; the muslces iliococcygeus, pubococcygeus and coccygeus which arise from the medial face of the pelvis and insert onto the proximal tail; the long, tendinous, tail muscles, flexor caudae brevis and longus; and the ventral and lateral set of segmental tail muscles. The innervation of the lumbar transversospinalis muscles by the medial branches and of lateral longissimus by the lateral branches of the dorsal rami of the spinal nerves was traced and confirmed by electrical stimulation of the nerve branches. The innervation of medial longissimus is also described. Additionally, movements of the vertebral column produced by direct unilateral or bilateral muscle stimulation were observed for a number of the muscles.

The potentiation effect of short tetani (5 sec, 50 Hz) of commissural fibers having dendritic synapses on CA1 pyramidal cells of the hippocampus was studied in freely behaving rats. High frequency stimulation produced a large increase in amplitude of the population spike and, to a lesser extent, of the extracellular synaptic responses. This increase was maintained for 4 days after a single train. The results imply that the efficiency of the synaptic transmission in the commissural path--CA1 pyramidal synapse can be modified.

The innervation of the bone marrow of the albino rat was investigated by electrostimulation and morphological methods. Stimulation of the lumbar sympathetic trunks resulted in the release of reticulocytes and neutrophils into the circulating blood. The effects of stimulation on other cell types in the bone marrow could not be definitely established. It was concluded that the nerve fibers to the bone marrow were distributed to the arteries. It is postulated that the transmitter substance released at the autonomic nerve endings may have an effect upon the permeability of the venous sinusiods and the mobility of the blood cells in the marrow parenchyma resulting in their release into the circulating blood.

1. The effects of various brain lesions on the responses of vestibular nuclear neurons (Vn) of the horizontal semicircular canal system to optokinetic stimulations were studied to elucidate the optokinetic path from the retina to the vestibular nuclei. A previous study performed in intact rats served as a control [2]. 2. It was shown that the pretectal region including the n. of the optic tract is the first central relay in the optokinetic path; it receives its functionally effective input from the contralateral eye. Unilateral lesions of this area rendered all Vn responses unidirectional when tested with binocular stimulation. Lesions of other visual centers such as the superior colliculi or visual cortices had no influence on the optokinetic response properties of Vn. 3. The area of the n. reticularis tegmenti pontis (NRTP) proved to be an important link between pretectum and vestibular nuclei: Unilateral lesions produced effects similar to those described for pretectal lesions. Pretectal axons to NRTP descend lateral to the MLF and tectospinal tract. 4. It was demonstrated that the vestibular commissure plays the crucial role in mediating the mirror image optokinetic effects to Vn on the opposite side and assures the bidirectionality of the responses to binocular stimulation. 5. Cerebellectomy did not significantly affect the Vn responses to the optokinetic stimuli presented in this study. 6. Electrical stimulation of the pretectum excited type II and inhibited type I Vn ipsilaterally and had the opposite effect on Vn located on the opposite side. NRTP stimulation excited type II and inhibited type I ipsilaterally; latency analysis of these effects suggested that the pretectal stimuli excited opsilateral NRTP neurons which, in turn, excited ipsilateral type II Vn. Ipsilateral type I inhibition as well as the concurrent contralateral type II inhibition and type I excitation are produced by the inhibitory action of type II on type I and the commisural system. 7. Systemic application of picrotoxin abolished all optokinetic responses of Vn except the type II activation. This finding further supports the hypothesis described above. 8. Unilateral pretectal or NRTP lesions abolished OKN to surround motion in the direction of the lesion.

Frequency-related isovolumetric contractions of the rat seminal vesicle elicited with transmural electrical stimulation were blocked by tetrodotoxin but unaffected by hexamethonium. The postganglionic motor innervation of the rat seminal vesicle is purely excitatory and contains both an adrenergic and a cholinergic component which are excited simultaneously during transmural stimulation. Contractions elicited by adrenergic nerve stimulation were mediated by norepinephrine acting via alpha adrenoceptors, i.e., 1) responses of untreated vesicles to transmural stimulation and to exogenous norepinephrine were antagonized by phentolamine and potentiated by cocaine, 2) pretreatment of animals with reserpine or 6-hydroxydopamine produced a marked depletion of tissue norepinephrine concentration and reduced the responses to transmural stimulation to a level which resembled that of untreated organs in the presence of phentolamine, 3) the residual responses of vesicles from pretreated rats were not modified by phentolamine or cocaine, and 4) responses to tyramine in untreated organs were antagonized by phentolamine but not by cocaine and were observed in organs from reserpine-pretreated rats only after repletion with exogenous norepinephrine. Responses elicited by cholinergic nerve stimulation were mediated by acetylcholine through muscarinic receptors, i.e., 1) responses of untreated vesicles to transmural stimulation and to exogenous acetylcholine were antagonized by atropine, 2) the residual responses to transmural stimulation of vesicles from animals pretreated with reserpine of 6-hydroxydopamine were nearly abolished by atropine and 3) physostigmine potentiated and prolonged the responses of organs from untreated and reserpine-pretreatd animals to transmural stimulation; these effects of physostigmine were abolished by atropine.

THE HEART OF THE ADULT RAT HAS LONG BEEN RECOGNIZED TO BE ANOMALOUS IN AT LEAST TWO RESPECTS: an absent or negative inotropic response to an increase in rate of electrical stimulation (negative staircase); resistance to digitalis glycosides. The heart of the neonatal rat (less than 2 weeks old), on the other hand, demonstrates a markedly positive staircase and a large increase in force upon application of glycoside. It is significant that the action potential of the neonate ventricle demonstrates a prolonged plateau component which progressively decreases with age. The shortening of the plateau correlates with the disappearance of the positive staircase and glycoside responses. Previous studies indicated that a major factor contributing to the prolonged plateau of the neonate was a high level of sodium (Na) conductance. Thus transmembranous Na movement associated with excitation is considerably greater in the neonatal heart as compared to the heart of the adult rat. The higher level of intracellular Na would produce increased activity of a proposed sodium-calcium (Na-Ca) carrier. This is believed to mediate the augmented influx of Ca which is responsible for positive staircase and glycoside responses. Ventricular muscle from the hearts of most mammalian species demonstrates a prolonged plateau with maintenance of a "slow" channel for Na. It appears that in the rat this channel closes with age. It follows that there would be a reduced tendency for the adult rat heart to accumulate intracellular Na, [Na](i), when excitation frequency is increased or the Na pump is inhibited by digitalis. Since elevation of [Na](i) is the stimulus for the proposed Na-Ca carrier, this system would not be activated, Ca influx would not increase and contractility would not be augmented.

Seventy-two hours after a 90 min period of electrical stimulation of the cervical sympathetic trunk, tyrosine hydroxylase activity was twice as high in homogenates of stimulated ganglia than in homogenates of contralateral control ganglia. When aliquots of the homogenates of the two groups of ganglia were mixed, the tyrosine hydroxylase activity was additive. Immunoprecipitation studies using an antibody prepared against purified tyrosine hydroxylase demonstrated that the doubling in enzyme activity is accompanied by a doubling in the amount of immunoprecipitable material. Thus the increase in tyrosine hydroxylase activity can be totally accounted for by an increase in the amount of tyrosine hydroxylase in the ganglion.

The right motor cortex was electrically stimulated in adult, awake rats for 45 min. Local cerebral glucose utilization (LCGU) was measured in white matter pathways with the (14C)-2-deoxyglucose method. Stimulation increased LCGU in focal regions of the right internal capsule to 51.3 mumol/100 g/min, compared to 39.8 on the control left side. Stimulation also increased LCGU in the right, medial pontine pyramidal tract to 36.2 mumol/100 g/min, compared with 27.3 on the control left side. The data demonstrate that electrical stimulation of motor cortex neurons increases LCGU 30 to 40% in the efferent myelinated axons of those neurons.

Central nervous system (CNS)-induced suppression on the muscle Na-pump activity was studied in soleus (SOL) muscles of hypokalemic rats. Peripheral nerve section, cervical soleus and brainstem transection, decerebration, and cortical spreading depression with 20% KCl activated the Na-pump in SOL muscles during hypokalemia. Blockage of the nerve conduction by tetrodotoxin (TTX) also activated the Na-pump in SOL muscles. The activation of Na-pump after the denervation was completely abolished by the pre-treatment of ouabain. However, the muscle cation contents were not affected by the injection of curare and atropine. The activation of Na-pump in the muscles after denervation in the curarized hypokalemic rats was completely removed by electrical stimulus of the distal nerve stump of cut sciatic nerve. alpha-Adrenoreceptor antagonists (phenoxybenzamine, phentolamine and dibenamine, and prazosin) stimulated the Na+ and K+ transports in the SOL muscles during hypokalemia while beta-adrenoreceptor antagonist (propranolol) had no effect. The denervation effect on SOL muscle cation contents was not affected with or without the presence of propranolol. It is concluded that CNS acts to inhibit the Na-pump mechanism in SOL muscles of hypokalemic rats and the inhibition is achieved by the apparent release of catecholamines onto muscle following neural activity. Thus, the CNS-induced suppression on the muscle Na-pump is prevented by denervation and by treatment with drugs that block either nerve conduction or alpha-adrenoreceptor.

To determine whether baroreflex sensitivity changes with age, we compared drug-induced reflex responses in 2- and 9-mo-old female Sprague-Dawley rats anesthetized with urethan-chloralose. Baroreflexes were stimulated by elevating or lowering blood pressure with intravenous infusions of phenylephrine or sodium nitroprusside. Reflex responses in heart rate and sympathetic nerve activity during phenylephrine infusions were weaker in 9- than in 2-mo-old rats, as were reflex tachycardia during sodium nitroprusside infusion and decreases in heart rate and sympathetic nerve activity elicited by electrical stimulation of the left aortic depressor nerve. Afferent aortic nerve activity was also appreciably lower in 9-mo-old rats at pressures greater than 130 mmHg but did not differ between rat groups at normotensive pressures. These results suggest that baroreflex sensitivity in 9-mo-old rats can be characterized as follows: 1) impaired at pressures greater than 130 mmHg but still adequate at normotensive pressures, and 2) all reflex arc components may be impaired.

Acetylcholine release from cortical slices superfused with choline-enriched Krebs solution containing physostigmine was investigated at birth, at 7, 20 and 30 days, and at 3 and 24 months of age, in order to assess age influence on the functional efficiency of the cortical cholinergic network. The slices were electrically stimulated at frequencies from 1 to 10 Hz for 5 min periods, preceded and followed by rest periods. The superfusate was collected every 5 min and acetylcholine content quantified by bioassay. In the newborn and 7 day-old pups acetylcholine release was approximately 50% lower than that of the 3 month-old rats at all frequencies tested. The highest release was elicited in the 30 day-old rats. Beginning with this age the evoked ACh release underwent a decline which in the 24 month-old rats brought it back to the same level as in the newborn ones. The blockade of the muscarinic autoreceptors by atropine 1.5 X 10(-8) M caused an increase in acetylcholine release at 20 day, 3 and 24 months of age but not in the newborn and 7 day-old pups. Adenosine 3 X 10(-5) M decreased acetylcholine output in newborn and adult but had no effect in the senescent rats.

The foreleg proprioceptive and cutaneous representations, in the Sm cortex of urethane-anesthetized rats was studied. Natural or electrical stimulations and stretches of single forearm muscles were used. Multiunitary, unitary or intra-cellular recordings were performed in the contra-lateral Sm cortex. The aims of the study were: 1- to compare the proprioceptive and cutaneous maps 2- to analyse the characteristics of the unitary responses and 3- to study the laminar distribution of cutaneous and muscular inputs. It is shown that: 1- the proprioceptive and cutaneous representations overlapped, except in the anterior part where only proprioceptive (mainly articular) responses were obtained. The representation of each stretched muscle extended over the whole cutaneous area, showing a total overlap between inputs from these muscles. 2- 46% of the intracellularly recorded cells (n = 215) responded to peripheral stimulation, and 30.7% were influenced by (at least) muscle stretch. The majority of excited cells showed cross-modal convergence, and among neurons responding to muscle stretch, 60% received inputs from the two muscles stretched. Two categories of EPSPs were found, and four neurons responded to cutaneous or muscular stimulation with a burst. 19% of the responding cells were inhibited by peripheral--mainly cutaneous--stimulation. 3- Excited neurons were recorded in all layers, with just over half located in layer IV, whereas IPSPs were obtained mainly in layer V. The cells excited by cutaneous and muscular inputs (convergent neurons) were preponderant in layers IV to VI. This work shows that the cutaneous and muscular inputs reach the same area in Sm cortex, and that a majority of excited cells are "convergent". The results are not in favor of an area 3a (by analogy with cats and monkeys) in the rat.

The pathway for chemoreceptor input to hypothalamic supraoptic nuclei has been examined in anaesthetised lactating and non-lactating rats. In lactating rats, the increase in intramammary pressure following bilateral carotid occlusion, which is probably mainly due to vasopressin, was abolished by lesions in the septum, but not by lesions in more caudal regions of the hypothalamus. In non-lactating rats, electrophysiological experiments demonstrated that the input from carotid body chemoreceptors to phasically-discharging supraoptic neurones is ipsilateral only. The effects of chemoreceptor stimulation on the neurones can be mimicked by electrical stimulation within the medial preoptic area and anterior hypothalamus in a region medial and rostral to the supraoptic nuclei. Lesions within this region abolish the chemoreceptor input to the supraoptic nuclei, but leave the baroreceptor input intact. It is proposed that chemoreceptor afferents to the supraoptic nuclei pass in the lateral hypothalamus to the region of the septum where they turn medially and descent through the medial part of the rostral hypothalamus. The results are discussed in terms of the general role of the chemoreceptor reflex and, more specifically, with respect to the possible significance of vasopressin in the control of arterial blood pressure.

The apparent lack of a positive staircase effect in ray myocardium may reflect inadequate metabolic support. Isolated rat hearts (n equals 10) were perfused at 37 degrees C with Krebs buffer containing 5 mM glucose. In 10 preparations increases in heart rate from 240 to 480/min resulted in twofold increases in left ventricular pressure and dP/dt. Pacing at a rate of 480/min resulted in mechanical deterioration of the preparation and in 50% decreases of myocardial ATP concentration within a 10-min period. Hearts of open-chest rats driven at the same rate for the same period maintained normal ATP stores. In isolated papillary muscles contracting isometrically at a rate of 30/min, peak stress 15g/mm2 (mean plus or minus SE, n equals 8) and was not changed by increasing the concentration of glucose from 5 to 30 mM. When frequency was raised from 30 to 300/min, stress declined to 5.0 plus or minus .15 g/mm2 in the presence of 5mM glucose (P smaller than .001) but increased to 8.8 plus or minus .21 g/mm2 (P smaller than 0.001) in the presence of 30 mM glucose. Thus, rat ventricular myocardium exhibits a positive staircase effect at physiological heart rates when metabolic support is adequate.

Experiments were performed in which the typical procedure for obtaining discriminated avoidance behavior with rats in a lever-pressing apparatus was compared with a new procedure which allowed only avoidance but not escape from the shock. When either escape or avoidance is possible, the rats make a majority of escape responses, but where escape is impossible avoidance behavior is rapidly established.