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In the present study, the relations between acidic and basic fibroblast growth factors (aFGF and bFGF, respectively), platelet-derived growth factor (PDGF), and food intake were studied. When aFGF-, bFGF-, and PDGF-like activity in cerebrospinal fluid (CSF) was examined by bioassay, the activity of those factors significantly increased in postfeeding CSF, compared to prefeeding CSF. Injections of aFGF, bFGF, aFGF 1–15 (synthetic amino-terminal peptide of aFGF), and PDGF into the third cerebral ventricle decreased food intake, and injections of anti-aFGF, anti-bFGF, and anti-aFGF 1–15 antibodies into the lateral hypothalamus (LHA) increased food intake. The activity of LHA glucose-sensitive neurons was inhibited by electrophoretic application of aFGF. These results suggest that aFGF, bFGF and PDGF have in vivo physiological roles in the central nervous system, distinct from those as mitogens.

Single neuron activity in the monkey lateral hypothalamus (LHA) was recorded by multibarreled electrode during a bar press feeding task. Activity of glucose-sensitive (GS) neurons decreased during bar press (BP) and reward (RW) periods. The inhibition was caused by activation of beta-adrenoceptors and opioid receptors respectively. Glucose-insensitive (GIS) neurons were excited during BP and RW, and at cue light (CL). Excitation at CL and BP was caused by activation of dopaminergic receptors. Among GS neurons, 66% responded to taste and 88% to odor. These responses were 39% and 52% in GIS neurons. GS neurons responded predominantly to two or more taste and odor stimuli while GIS neurons responded to only one stimulant. GS neurons have dense mutual connections with the prefrontal area, and GIS neurons are connected with the motor area. Gustatory and olfactory stimulation elicited responses in 67% of GS neurons and in only 21% of GIS neurons. Data suggest that GS and GIS neurons may have different functions in feeding: GS neurons process endogenous chemical information and integrated chemical sensations, and GIS neurons process external information processing, motor control and discriminative chemical sensations.

Brain microdialysis was used to determine if lateral hypothalamic serotonin (5-HT) is involved in the mazindol-induced anorexia in rats. Direct application of mazindol through a microdialysis membrane both significantly increased the 5-HT levels in the lateral hypothalamus and suppressed food intake by fasted rats. The increase in 5-HT concentration was dose related and the concentration of mazindol for half-maximal response was 4.6 microM. Pretreatment with methysergide, a potent 5-HT receptor-blocking agent, significantly antagonized the mazindol-induced anorexia. These results suggest that the anorectic action of mazindol might be mediated, at least in part, through serotonergic mechanisms in the hypothalamus.

Antisera against acidic fibroblast growth factor purified from bovine brain were produced in rabbits and used for immunohistochemical study of the rat brain. When examined in an immunospot assay using a nitrocellulose membrane, the best antibody was capable of detecting 80 fmol of acidic fibroblast growth factor but failed to react even with up to 5 pmol of basic fibroblast growth factor. Using this antiserum, the immunohistochemical distribution of acidic fibroblast growth factor was examined in rat brain. Acidic fibroblast growth factor-like immunoreactivity was localized mainly in a subpopulation of ependymal cells and tanycytes, as well as in some glial cells. Positive ependymal cells were observed throughout the walls of ventricles, including the third ventricle and cerebral aqueduct. Immunoreactive processes of tanycytes were found extending from the ventral wall of the third ventricle to the brain parenchyma and surface. The most intense immunostaining was observed in circumventricular organs such as the organum vasculosum laminalis terminalis and the subfornical organ. Particularly in the latter organ, there was an extremely dense plexus of immunoreactive fibers and processes around the wall of capillaries. The present results suggest that the effects of acidic fibroblast growth factor on brain functions may be exerted through the circumventricular organs and/or ependymal cells.

Orexin-A (ORX-A) and orexin-B (ORX-B) play critical roles in the regulation of sleep-wakefulness and feeding. ORX neurons project to the pedunculopontine tegmental nucleus (PPT), which regulates waking and rapid eye movement (REM) sleep. Thus, we examined electrophysiological effects of ORXs on rat PPT neurons with a soma size of more than 30 microm. Whole cell patch clamp recording in vitro revealed that ORX-A and ORX-B depolarized PPT neurons dose-dependently in normal and/or tetrodotoxin containing artificial cerebrospinal fluids (ACSFs), and the EC(50) values for ORX-A and ORX-B were 66 nM and 536 nM, respectively. SB-334867, a selective inhibitor for ORX 1 (OX(1)) receptors, significantly suppressed the ORX-A-induced depolarization. The ORX-A-induced depolarization was reduced in high K(+) ACSF with extracellular K(+) concentration of 13.25 mM or N-methyl-d-glucamine (NMDG(+))-containing ACSF in which NaCl was replaced with NMDG-Cl, and abolished in high K(+)-NMDG(+) ACSF or in a combination of NMDG(+) ACSF and recordings with Cs(+)-containing pipettes. An inhibitor of Na(+)/Ca(2+) exchanger and chelating intracellular Ca(2+) had no effect on the depolarization. Most of PPT neurons studied were characterized by an A-current or both A-current and a low threshold Ca(2+) spike, and predominantly cholinergic. These results suggest that ORXs directly depolarize PPT neurons via OX(1) receptors and via a dual ionic mechanism including a decrease of K(+) conductances and an increase of non-selective cationic conductances, and support the notion that ORX neurons affect the activity of PPT neurons directly and/or indirectly to control sleep-wakefulness, especially REM sleep.

The concentration of acidic fibroblast growth factor (aFGF), which is found in cerebrospinal fluid (CSF), markedly increases after the start of feeding. Food intake was dose-dependently suppressed by picomole amounts of aFGF introduced into the third cerebral ventricle and facilitated by addition of anti-FGF antibody. The ependymal cells, where aFGF is produced, release aFGF by responding to glucose increase in CSF after feeding. Released aFGF diffused into the brain parenchyma and was taken up by neurons in the hypothalamus and hippocampus. Emotional and spatial learning and memory were significantly more reliable after introducing aFGF into the hippocampus. Marked dose-dependent increases in plasma ACTH and corticosterone were detected from 20 min to 2 h after intracerebroventricular or intravenous administration of aFGF. Plasma epinephrine and norepinephrine also increased markedly for up to 120 min. Concomitant increases occurred in the activity of efferent sympathetic nerves. These findings suggest that aFGF activates the hypothalamic–pituitary–adrenal axis and sympathetic outflow. The effects of aFGF on phagocytosis in peritoneal macrophages from thioglycollate-treated mice were examined using flow cytometry. Phagocytosis of fluorescein isothiocyanate-labeled latex particles was enhanced by aFGF in a dose-dependent manner. When viewed together these results indicate that aFGF is not only one of the most potent substance yet found for the suppression of feeding, but it is also extremely effective in memory facilitation and sympathetic activation as well as biodefence.

A novel taste stimulus delivery technique along with a simple electronic onset marking system, designed for complex, neurophysiological-behavioral experiments in awake monkeys, are described. Intraoral implantation of a polyethylene tubing fistula enabled us to perform repeated, well-standardized application of various taste solutions to broad areas of gustatory receptors on the tongue, palate, pharynx and epiglottis, while activity of single neurons was extracellularly recorded in behaving rhesus monkeys. By introducing an electronic marking system, onset and duration of the stimulation could be determined.

Brain microdialysis plus high performance liquid chromatography and electrochemical detection were employed to study whether glutamate exerts direct presynaptic facilitation of dopamine (DA) release in the rat striatum. The perfusion of the dialysis probe with high-K+ Ringer solution (70 mM) increased DA and glutamate release 380.6 +/- 69.2% and 323.0 +/- 46.6% of preperfusion levels, respectively. Perfusion of 1 mM glutamate stimulated DA release by 250.7 +/- 30.6%, and coadministration of 2 mM glutamic acid diethylester (glutamate receptor blocking agent) significantly antagonized the glutamate response. The present results indicate presynaptic facilitation of the release of DA in the striatum by glutamate.

To elucidate the anorectic action of the endogenous organic acid, 3-hydroxybutyric acid (3-HBA), its effects on neurons in both the rat ventromedial hypothalamic nucleus (VMH) and the lateral hypothalamic area (LHA) were examined. Iontophoretic application of 3-HBA significantly facilitated the firing rate of VMH neurons, whereas facilitation and inhibition were observed in the LHA. These responses were specific to the glucoreceptor neurons in the VMH and glucose-sensitive neurons in the LHA. Intracellular recordings from brain slice preparations revealed that 3-HBA depolarized the cell membrane of the VMH neuron with an associated increase of membrane input resistance. This was similar to the effect of glucose on glucoreceptor neurons in the VMH. These results suggest that 3-HBA may modulate hypothalamic chemosensitive neuron activity as well as function as an endogenous satiety factor.

Fetal ventromedial hypothalamic (VMH) tissue was transplanted into or around the third ventricle of adult Fischer 344 rats to determine if transplanted VMH tissue could reverse the hyperphagia and obesity produced by bilateral VMH electrolytic lesions. Host VMH-lesioned rats received stereotaxic implants of 13 to 19 postcoitus fetal VMH tissue from normal Fischer pups. The results show that: 1) Fetal VMH tissue survived in the brain (mainly in the third ventricle) of VMH-lesioned rats. The optimal survival and differentiation was at the gestational age of 13 days; 2) VMH-lesioned rats containing VMH grafts tended to consume less food than the controls, but this was not statistically significant. Neural grafts that could compensate the hyperphagia and obesity produced by the VMH lesions (in comparison to the controls) were those placed into the third ventricle; 3) Electrophysiological evidence demonstrated that VMH grafts contain glucoreceptor neurons in grafts not only located in the third ventricle, but also in the thalamus; 4) Immunohistochemical evidence showed the presence of serotonin, β-endorphin and substance P immunoreactive fibers in the grafts. These results indicated that transplants of fetal VMH tissue in the brain of bilateral VMH-lesioned adult rats may have some functional effects (depending on the location of the graft).

Ghrelin is an endogenous ligand for the growth hormone (GH) secretagogue (GHS) receptor (GHS-R) and a potent stimulant for GH secretion even in infantile rats before puberty. Although the ventromedial nucleus of the hypothalamus (VMH) might be a site of action for ghrelin to induce GH release, the electrophysiological effect of ghrelin on VMH neurons in infantile rats remains to be elucidated. Thus, the purpose of the present study was to investigate the effect of ghrelin on VMH neurons using hypothalamic slices of infantile rats. Ghrelin excited a majority of VMH neurons in a concentration-dependent manner. VMH neurons that were excited by GH releasing peptide-6 (GHRP-6), a synthetic GHS, were also excited by ghrelin and vice versa. Repeated application of ghrelin to the same VMH neuron decreased progressively the excitatory responses depending on the number of times it was administered. The excitatory effect of ghrelin on VMH neurons in normal artificial cerebrospinal fluid (ACSF) persisted in low Ca2+-high Mg2+ ACSF. The present results indicate that (1) ghrelin excites a majority of VMH neurons dose-dependently and postsynaptically and (2) the excitatory effects of ghrelin are mimicked by GHRP-6 and desensitized by repeated applications of ghrelin.

Experiments were performed on male Wistar rats at 8 weeks of age(Sankyo Lab., Shizuoka, Japan) and approved by the InstitutionalAnimal Care and Use Committee of the Faculty of Engineering ofToyama University. Rats were housed in a light-controlled room(light on, 06:00–18:00) at a temperature of 23 ± 1°C. Food and waterwere available

Leptin, a product of the ob gene, decreases food intake and body weight in both Wistar and Zucker obese rats when administered centrally or peripherally. To examine whether these leptin effects might be mediated through aneuropeptide Y (NPY) signaling pathway in the medial part of the arcuate nucleus of the hypothalamus (vmARC), the effects of leptin on vmARC neurons in Wistar and Zucker obese rats were examined electrophysiologically using brain slice preparations. Bath application of leptin inhibited about 60% of the vmARC neurons recorded in slices from Wistar rats. Similar inhibitory effects of leptin on vmARC neurons were also observed under low-Ca 2 + , high-Mg 2 + Ringer's solution. However, inhibitory effects were almost absent under Ringer's solution containing a protein kinase C inhibitor, chelerythrine chloride. In slices from Zucker obese rats, leptin inhibited only about 25% of the vmARC neurons recorded, and the proportion of neurons inhibited was significantly smaller for these rats than for Wistar rats. These results suggest that reductions in food intake and body weight induced by leptin in both Wistar and Zucker obese rats are partly mediated via inhibition of an NPY signaling pathway in the vmARC.

Glucose-sensitive neurons in the lateral hypothalamic area produce orexin-A (hypocretin-1) and orexin-B (hypocretin-2) and send their axons to the hippocampus, which predominantly expresses orexin receptor 1 showing a higher sensitivity to orexin-A. The purpose of the present study was to assess the effects of orexin-A on the performance of Wistar rats during the Morris water maze test and then to determine the effects of orexin-A on both the long-term potentiation and long-term depression in Schaffer collateral/commissural-CA1 synapses in hippocampal slices. The results of the Morris water maze test show that 1.0 and 10 nmol of orexin-A, when administered intracerebroventricularly, retarded spatial learning. A probe test examined after training of water maze task also showed an impairment in spatial memory. The results of an electrophysiological study using hippocampal slices demonstrated that 1.0 to 30 nM of orexin-A applied to the perfusate produces a dose-dependent and time dependent suppression of the long-term potentiation. In addition, the long-term depression was not affected by orexin-A. The results of a paired-pulse facilitation experiment indicated that the effects of orexin-A were post-synaptic and not due to presynaptic transmitter release. These results show that orexin-A impairs spatial performance and these impairments can be attributed to a suppression of long-term potentiation in the Schaffer collateral-CA1 hippocampal synapses.

Cholecystokinin (CCK) is deeply involved in the control of learning and emotional behaviors. The authors characterize the behavioral properties of Otsuka Long Evans Tokushima Fatty (OLETF) rats, which lack the CCK-A receptor because of a genetic abnormality. In the Morris water-maze task, the OLETF rats showed an impaired spatial memory. In the inhibitory avoidance test, they showed facilitating response 24 h after training. Hypoalgesia was observed in a hot-plate test. In the elevated plus-maze and food neophobia test, OLETF rats showed an anxiety-like response. In addition, OLETF rats were hypoactive in the Morris water-maze and the elevated plus-maze. The results suggest that the OLETF rats showed a spatial memory deficit, hypoactivity and anxiety due, at least in part, to the lack of CCK-A receptors.

Endogenous sugar acid 2-buten-4-olide, a satiety substance, has been shown to increase the blood glucose, norepinephrine, and glucocorticoid concentrations that are known to modulate learning and memory processes. The glucose-induced release of acidic fibroblast growth factor facilitated the hippocampus-dependent memory function. In the present study, we investigated the effect of 2-buten-4-olide on the spatial performance of male DDY mice undergoing the water maze task. The intraperitoneal injection of 2-buten-4-olide (5 mg/kg) facilitated the spatial performance, which was indicated by a reduction in the escape latency in which the mouse finds and climbs the goal platform in comparison to the vehicle-injected control mice. In the probe test after removing the platform, the 2-buten-4-olide-treated mice stayed a longer time in the quadrant where the platform was originally located and crossed more frequently at the platform location than did the control mice. The pretreatment of acidic fibroblast growth factor antibody injected into the lateral ventricle eliminated the effect of 2-buten-4-olide both during the training sessions and during the probe test. Therefore, 2-buten-4-olide was found to improve the spatial performance, and this effect is mediated, at least in part, by acidic fibroblast growth factor.

The lateral hypothalamic area (LHA) and the ventromedial hypothalamic nucleus (VMH) have historically been implicated in ingestive behavior, energy balance and body mass regulation. The LHA is more closely associated with the initiation of eating; whereas the VMH mediates the cessation of eating. The parvocellular part of the paraventricular nucleus (pPVN) is also included in the suppressing mechanism. Recently, two hypothalamic peptides, orexin-A and orexin-B, localized in the posterior and lateral hypothalamic perifornical region were discovered in the rat brain and they increase food intake. Leptin, a protein encoded by an obesity gene, expressed in adipose tissue and released into the blood also affects food intake. Orexin and leptin receptors have been localized in the LHA, pPVN, and VMH. The purpose of this study was to measure food intake in the rat in response to leptin and orexin-A; and to determine their electrophysiological effects on feeding related hypothalamic neurons. Results clearly show that leptin suppresses food intake whereas orexin-A increases food intake. These differences are associated with leptin and orexin-A modulatory effects on LHA, pPVN, and VMH glucose responding neurons. In the LHA, leptin inhibits a larger proportion of both glucose-sensitive neurons (GSNs) and non-GSNs. In the pPVN, leptin increases more GSNs in comparison to non-GSNs. Whereas in the VMH, leptin increases the activity of glucoreceptor neurons (GRNs) in comparison to non-GRNs. Orexin-A had opposite effects: increases activity of GSNs more than the non-GSNs in the LHA and significantly suppresses GRNs in the VMH. In the pPVN, orexin-A had no observable effects on neurons that have a low density of orexin 2 receptors. Results are discussed in terms of hypothalamic neural circuits that are sensitive to endogenous food intake inducing and reducing substances.

Clinical problems related to eating, reproduction, emotion, and immunity have been demonstrated to be influenced by environmental changes including temperature and meteorological phenomena. The hypothalamus is well known to be involved in homeostatic control of body temperature, ingestion, reproduction, and biodefense to allow survival for both individuals and species. The hypothalamus contains specific neurons responding to changes in temperature, glucose, and sex hormones. Warm-sensitive neurons and glucoreceptor neurons have been shown to be excited by pyrogen and estrogen. Bidirectional facilitative control of glucose utility and estrogen receptors is found in the hypothalamus and this modulates thermoregulation. These findings suggest that the different homeostatic mechanisms link together in the hypothalamus. Environmental problems, such as global warming and environmental endocrine disrupters, may disturb our adaptive function in which the hypothalamus plays an essential role.

The tissue concentration of lipid peroxides was determined in the brain, heart, liver, lung and kidney of accelerated senescence-prone (SAMP-8) and -resistant (SAMR-1) mice at 3, 6 and 9 months of age by a method involving chemical derivatization and high performance liquid chromatography. The level of lipid peroxides in the brain did not show an age-dependent change, but at each age the brain level of lipid peroxides was significantly higher in SAMP-8 than in SAMR-1. In contrast, the lipid peroxide levels in the peripheral organs showed increases with aging in both strains, and they were significantly higher in SAMP-8 than in SAMR-1 at both 3 and 6 months of age (except at 3 months of age in the kidney). These results suggest that increased oxidative stress in the brain and peripheral organs is a cause of the senescence-related degeneration and impairments seen in SAMP-8.

LI, A.-J., Y. OOMURA, K. SASAKI, K. SUZUKI AND T. HORI. Protective effect of acidic fibroblast growth factor against ischemia-induced learning and memory deficits in two tasks in gerbils. PHYSIOL BEHAV 66 (4) 577–583, 1999.—The influence of transient forebrain ischemia on behavioral performance, and the effect of intracerebroventricular (i.c.v.) injection of acidic fibroblast growth factor (aFGF) on such ischemia-induced deficits were examined in Mongolian gerbils by assessing learning and memory in two tasks: passive avoidance and Morris water maze. A 5-min period of forebrain ischemia led to learning and memory deficits in both tasks, and also to neuronal death in the hippocampal CA1 region. Continuous i.c.v. infusion of aFGF bilaterally into the lateral ventricules by osmotic minipumps over 2 days before, and 5 days after the ischemia (a total of 3.6 μg/gerbil) largely prevented both the ischemia-induced behavioral deficits and the neuronal death in the hippocampus. These observations suggest that the hippocampus is a critical site for the performance of the two tasks, and that aFGF has a protective effect against such ischemia-induced learning and memory deficits in gerbils.

To characterize the effects of acidic fibroblast growth factor (aFGF) in mouse peritoneal macrophages, the effects of aFGF fragments on phagocytosis were examined. Fragments that were tested included aFGF(1-15), aFGF(1-20), aFGF(1-29), Ala16-aFGF(1-29), aFGF(9-29) and aFGF(114-140). aFGF(1-29) induced an enhancement of phagocytosis in a dose-dependent manner and was more effective than any other fragments tested. Even in Ca2+-and Mg2+-free solutions, phagocytosis was enhanced by aFGF(1-29). However, the enhancement induced by aFGF(1-29) was completely inhibited in the presence of mannan (4 mg/ml). Furthermore, the enhancement of phagocytosis by aFGF(1-29) was suppressed by heparin (100 microg/ml). The results of the present study suggest that the active region of aFGF that is responsible for the enhancement of phagocytosis corresponds to residues 15-29 and that phagocytosis, which is modulated by aFGF, is independent of extracellular Ca2+ and is mediated by mannose receptors.

Effects of a pre-training intraperitoneal glucose injection on learning and memory were tested using two tasks: passive avoidance and Morris water maze. In the former task, mice that had received glucose 2 h prior (but not 1, 3, or 5 h prior) to a trial that combined acquisition with passive avoidance of foot shock showed a significantly increased retention latency when tested 24 h later. Thus, this effect was time-dependent, and it was also found to be dose-dependent by further experiment. In contrast, 2-deoxy- d -glucose and fructose had no such effect. In the Morris water maze task, glucose injection 2 or 3 h before a block of trials enhanced the spatial memory performance of mice. These glucose-induced memory-facilitation effects were abolished by an intracerebroventricular injection of anti-acidic fibroblast growth factor antibody 30 min before the glucose injection, suggesting a critical role for endogenous acidic fibroblast growth factor in this facilitatory effect. Furthermore, continuous intracerebroventricular infusion of acidic fibroblast growth factor in rats significantly increased retention latency (when tested repeatedly on successive days using a passive avoidance task). Our earlier studies demonstrated that brain acidic fibroblast growth factor is produced in the ependymal cells of the cerebroventricular system, and is released into the cerebrospinal fluid following either a meal or a (intraperitoneal or intracerebroventricular) glucose injection. This released acidic fibroblast growth factor also diffuses into the brain parenchyma, and is taken up by neurons in the hippocampus, hypothalamus, and elsewhere in the brain some 2 h after the meal or glucose injection. These and the present findings indicate (i) that pre-training glucose injection improves memory performance, and (ii) that acidic fibroblast growth factor, especially by its action within the hippocampus, is involved in this enhancement process.

The effects of acidic fibroblast growth factor (aFGF) on phagocytosis in peritoneal macrophages from thioglycollate-elicited mice were examined using flow cytometry. aFGF enhanced phagocytosis of fluorescein isothiocyanate-labeled latex particles in a dose-dependent manner. Basic fibroblast growth factor (bFGF) also enhanced phagocytosis. This study suggests that aFGF can modulate an important activity of macrophages.

Effects of acidic fibroblast growth factor (aFGF), an endogenous satiety substance, on the hypothalamic-pituitary-adrenocortical axis were examined under pentobarbital sodium anesthesia in rats. A guide cannula was inserted into the cerebral third ventricle and a vascular indwelling catheter was inserted into the right atrium from the jugular vein 2 wk and 3 days, respectively, before the experiment. A marked dose-dependent increase in plasma corticosterone was detected from 20 min to 2 h after intracerebroventricular administration of aFGF (1–10 ng). Significant increases in plasma adrenocorticotropic hormone (ACTH) were observed from 5 to 150 min after the intracerebroventricular administration of 10 ng aFGF. Significant dose-dependent increases in plasma corticosterone were also observed after intravenous injections of aFGF (1, 10, and 100 ng), together with increases in the plasma ACTH level. Pretreatment with antibody to corticotropin-releasing factor via the intracerebroventricular route abolished the increases in corticosterone induced by intracerebroventricularly administered aFGF, but not those induced by intravenous injection of aFGF. In adrenal glands perfused in situ with artificial medium, the corticosterone secretion rate increased slightly in response to 10−9M aFGF. These findings suggest that intracerebroventricular administration of aFGF activates the hypothalamic-pituitary-adrenal axis via corticotropin-releasing factor release in the brain, whereas peripheral administration of aFGF activates adrenocortical secretion mainly via a direct action on ACTH release.

The effects of recombinant human interleukin-6 (rhIL-6) on long-term potentiation (LTP) induced in the Schaffer collateral/commissural-CA1 pathway were examined using rat hippocampal slices. Field excitatory postsynaptic potential was recorded in the stratum radiatum of the CA1 region. Ten-min applications of rhIL-6 (50-2000 U/ml), started 5 min before the tetanus, significantly inhibited the induction of LTP, and in high doses of rhIL-6 also inhibited short-term potentiation (over 200 U/ml) and post-tetanic potentiation (over 500 U/ml). The effects of rhIL-6 (500 U/ml) were completely abolished by the preincubation of the slices with monoclonal anti-IL-6 receptor antibody (16 microg/ml) for 2 h. Heat-inactivated rhIL-6 had no effect on the synaptic potentiation. RhIL-6 affected neither the previously established LTP nor the basal synaptic transmission. These findings indicated that rhIL-6 modulated synaptic potentiation through the IL-6 receptor-mediated process in the hippocampus, probably by affecting post- and presynaptic sites in the CA1 region. The possible mechanisms of the IL-6-induced suppression of the synaptic potentiation were discussed.

Senescence-accelerated mouse (SAMP8) is known as a murine model of accelerated aging and memory dysfunction. The binding activity of [3H] 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxam ide (PK-11195) as a neurochemical marker of gliosis markedly increased with aging in the cerebral cortex and hippocampus of SAMP8. Immunoreactivity for glial fibrillary acidic protein (GFAP) was also enhanced. A beta-amyloid precursor protein (APP)-like immunoreactivity and 27-kDa-carboxyl terminal fragments of APP increased in SAMP8 brain. In addition, anti-APP antibody stained reactive astrocytes surrounding spongy degeneration in brain stern of SAMP8. These results suggest that astrocytosis and production of APP-derived fragments occur markedly in SAMP8 brains.

The effects of acidic fibroblast growth factor (aFGF), basic FGF (bFGF), and related peptides, such as aFGF fragments, on food and water intake were investigated. Infusion of aFGF and bFGF into the third cerebral ventricle significantly suppressed food intake. The potency of aFGF was 1.5 that of bFGF in food intake inhibition. Both FGFs also suppressed water intake. Infusion of a carboxyl-terminal fragment of aFGF, aFGF-(114-140), did not affect food intake, whereas an amino-terminal fragment of aFGF, aFGF-(1-15), was significantly inhibitory. Other amino-terminal fragments, aFGF-(1-20) and aFGF-(1-29), did not affect food intake. However, [Ala16]aFGF-(1-29), in which the cysteine residue at position 16 was replaced with alanine, significantly suppressed food intake. Infusions of functional antagonists for FGFs, anti-aFGF, anti-bFGF, and anti-aFGF-(1-15) IgGs, into the lateral hypothalamus significantly increased food intake. The results suggest that: aFGF, bFGF, and some amino-terminal peptides of aFGF participate in the central regulation of food intake; the lateral hypothalamus is involved in their feeding suppression actions; and these peptides may function as physiologically relevant substances in the adult central nervous system, other than as neurotrophic factors.

The localization of fibroblast growth factor receptor-1 was investigated in rat brain by immunohistochemistry using a polyclonal antibody against an acidic peptide sequence of chicken fibroblast growth factor receptor-1. For raising the antisera in rabbits, we synthesized the oligopeptide EDDDDEDDSSSEEKEAD which is a highly acidic region of chicken fibroblast growth factor receptor-1. The oligopeptide was used as a haptenic antigen by conjugating with poly- l -glutamate as a carrier protein. On immunospot assay, the best antiserum was capable of detecting 15.7 pmols of both the chicken and its analogous human oligopeptides but failed to react even with up to 1 nmol of poly- l -glutamate. When rat brain homogenate was examined by Western blots, the antiserum revealed two bands with molecular weights of 145,000 and 75,000 corresponding to known sizes of the membrane-bound and secreted forms of the rat receptor, respectively. Immunohistochemistry in rat brain demonstrated that putative fibroblast growth factor receptor-1 immunoreactivity sites were present mainly in neurons but also in tanycytes and ependymal cells. Positive neurons were distributed widely in various brain regions, but were particularly abundant in such regions as the lateral hypothalamus, substantia nigra, locus coeruleus and raphe nuclei. The present study suggests that fibroblast growth factor receptor-1 is expressed preferentially in certain neuronal systems that appear to be under the influence of fibroblast growth factors in the normal brain. The result should facilitate study of the functional significance of fibroblast growth factors in these brain neurons.

“Umami” is the term proposed by Ikeda in 1909 to represent the taste of glutamate, the salt of the amino acid he had isolated from flavor-enhancing sea tangle. It has since been shown to be transduced by specific protein receptor molecules in a variety of animals [1]. Peripheral and central taste neurons are responsive to monosodium glutamate (MSG), and some show exclusive sensitivity to it. In multidimensional taste spaces generated from either human psychophysical or rat electrophysiologic data, MSG lies beyond the tetrahedron created by connecting the positions of the four traditional basic taste stimuli [2,3]. This fact implies that the taste of MSG cannot be accounted for by any combination of these basic stimuli. MSG is typically situated closer to NaCI than it is to sucrose, HCI, or quinine, suggesting a salty component to its taste. Yet when sodium transduction was disrupted in the rat by lingual application of amiloride, the impact on MSG’s response was minimal, and its neural code remained unaltered [4]. Therefore MSG presumably elicits a taste quality that transcends saltiness—one whose identity is sustained even as saltiness is largely blocked.

Acidic fibroblast growth factor (aFGF) in rat CSF increased 1000 times in the 2-h period after food intake, or IP, or ICV glucose infusion. The ICV application of aFGF dose dependently depresses and anti-aFGF antibody facilitates food intake. aFGF is produced in the ependymal cells and released into the CSF in response to increased glucose in the CSF caused by food intake. Released aFGF diffused into the brain parenchyma and was taken up into neurons in the hypothalamus, hippocampus, amygdala, etc. IP injection of glucose 2 h before a task that combined acquisition with passive avoidance significantly increased retention of avoidance by mice tested 24 h later. In a Morris water maze task, IP glucose injection 2 h before a first trial block reduced time to find and climb onto a platform hidden just below the water surface. The glucose facilitation of these affective and spatial memory were abolished by pretreatment with anti-aFGF antibody applied ICV. Continuous ICV infusion of aFGF into rats also significantly increased the reliability of passive avoidance for several days. After food intake, centrally released aFGF reaches the hippocampus and facilitates memory; peripherally released cholecystokinin reaches the endings of the afferent vagal nerves in the portal vein and changes their activity, which modulates hippocampal activity, to lead to memory facilitation. This, however, is blocked by vagotomy below the diaphragm. The results indicate the importance of food intake, not only to maintain homeostasis, but also to prepare a readiness state for memory facilitation.

To investigate the direct actions of neurotropin (NSP, a nonproteinaceous extract from inflamed skin of rabbits which is in therapeutic use), intracellular recordings were made from neurons of the ventromedial hypothalamic nucleus (VMH) and lateral hypothalamic area (LHA) in slices of guinea pig brain. In the VMH, NSP, applied by perfusion (0.1-3.0 NU/ml), caused dose-dependent depolarization in 29 of 48 neurons (60%) tested. No change in membrane resistance was observed during the depolarization, which hypothesized that the NSP-induced depolarization might be mediated through the inactivation of the Na-K pump. The NSP-induced depolarization persisted even after the elimination of synaptic activity by perfusion with Ca(2+)-free and high Mg2+ Ringer solution. NSP hyperpolarized the cell membrane of three neurons (6%) while two neurons (4%) showed biphasic responses; transient depolarization followed by long-lasting hyperpolarization. Membrane potential of the remaining 14 neurons was not changed by application of NSP. Of 14 LHA neurons tested for NSP effects, eight (57%) were depolarized, three (21%) were hyperpolarized, and one showed a biphasic response. The present results suggest that NSP significantly modulates hypothalamic neuron activity, and the central modulation of autonomic functions by NSP might be mediated through hypothalamic neurons.

Trophic actions of alpha-sialyl cholesterol (SC) and its sialidase-tolerant derivative, alpha-(3 beta-hydroxysialyl) cholesterol (SCt), were carried out on the development of midbrain neurons both in vitro and in vivo transplantation studies. Low to moderate concentrations of SC (0.01 to 0.05 micrograms/ml) facilitated neurite extension but had no effects on cell survival of primary cultured midbrain neurons. However, high concentration of SC (0.1 micrograms/ml) disturbed both neurite genesis and cell survival. SCt had a similar effect on midbrain neurons. At higher concentrations, SC and SCt induced concentration-dependent morphological changes in astrocytes from flat to fibrous. The effect on astrocytes was stronger in SCt than SC. At highest concentration tested (20 micrograms/ml), the proliferation of astrocytes was completely blocked, cells became detached and finally died. This effect of SC and SCt was partially blocked by simultaneous application of aFGF. Following dopaminergic cell grafting in vivo, SC and SCt had biphasic effects: a low dose (0.2 mg/kg, SC) enhanced motor recovery at 4 and 6 weeks after transplantation, while the highest dose (20 mg/kg, SC) disturbed motor recovery at all periods tested. These effects on motor recovery were paralleled by an effect on neurite genesis as studied by tyrosine hydroxylase immunostaining. Thus, at low concentrations, SC and SCt are neurotrophic agents that stimulate the development and differentiation of dopaminergic neurons.

Using microfluorometry, effects of acidic fibroblast growth factor (aFGF) on the in vitro ischemia-induced intracellular calcium elevation were investigated in gerbil hippocampal slices at 35 degrees C. When slices were superfused with hypoxic and glucose-free medium, the mean latency of the in vitro ischemia-induced calcium elevation was 209 +/- 51 s. The addition of aFGF in medium (25 micrograms/l) delayed the calcium elevation throughout the experiments: the mean latency was 541 +/- 94 s. This retardation in calcium elevation may be indicative of neuroprotective nature of aFGF.

Ischemic insult induces neuronal death in the CA1 subfields of the hippocampus which are designated generally as the most vulnerable brain region. Recent studies have shown that acidic and basic fibroblast growth factors are potent trophic factors that support the survival of neurons in many brain regions including the hippocampus. Here we demonstrate that continuous infusion of acidic fibroblast growth factor into the lateral cerebral ventricles beginning 2 days before ischemia prevents the death of the CA1 pyramidal cells in the hippocampus of gerbils. Furthermore, delayed continuous administration of acidic fibroblast growth factor starting 5 min after ischemia is equally protective. The results suggest a possible physiological function for acidic fibroblast growth factor in the normal support of hippocampal CA1 pyramidal cells and neurons in some other brain regions in considering the broad spectrum of responsive neurons.

The effects of electrical (ES) and chemical stimulations of the hypothalamus were investigated in monkeys during bar-press feeding. ES elicited both prolonged and nonprolonged types of suppression of bar-press feeding in hungry animals. Prolonged type suppression persisted for greater than 1 min beyond one or more post-ES trials and was found after ES of the dorsomedial hypothalamus (DMH), the ventromedial hypothalamus (VMH), and the ventromedial part of the lateral hypothalamic area (LHA). Non-prolonged type suppression was observed only during ES at some sites of both in hypothalamic and extrahypothalamic areas. A microinjection of glutamate into the VMH and the DMH, but not into the LHA, was able to reproduce the ES-induced prolonged type suppression. In contrast, the ES of the LHA, but not the VMH and DMH, in a satiated state provoked feeding. The results, together with the previous findings, suggest that the neuronal inhibitory mechanism of feeding exists in the VMH and DMH, while both the neuronal facilitatory and axonal inhibitory mechanisms in the LHA are involved in the feeding regulation, and these mechanisms of the LHA are affected by the hunger/satiety state.

Regional differences in the effects of electrical (ES) and chemical stimulation on execution of a bar-press feeding task, and in neuronal activity related to feeding, glucose sensitivity, and odor responsiveness were examined in the lateral hypothalamic area (LHA) of monkeys. In satiated animals, ES of the far lateral and ventral LHA induced bar-press feeding. In hungry animals, ES of the dorsal LHA suppressed the feeding task only during the stimulation period, but prolonged feeding suppression that occurred after ES of the ventromedial LHA. Microinjection of Na-glutamate into LHA sites where ES was effective in suppressing feeding had no effect, but it was effective in the medial hypothalamus. Glucose-sensitive (GS) neurons decreased in activity during bar pressing and/or during the ingestion period. Glucose-insensitive (GIS) neurons showed a cue-related excitation more often than GS neurons. Odor-responding GS and GIS cells were localized in ventromedial and lateral LHA sites, respectively. The present study suggests the regional heterogeneity of the LHA in feeding regulation, depending on both hunger and satiety states.

We electrically stimulated the midbrain of male rhesus monkeys seated in a restraint chair facing the female partners and examined whether sexual behavior could be induced. When the midbrain was stimulated (0.2 ms, 50-500 microA and 50 Hz for 2.5 s), the male monkey touched and held the waist of his partner (latency; 0.9 +/- 0.4 s, mean +/- SD, n = 225), and then mounted her when she responded with presenting her hip toward him. However, this mounting, unlike when the hypothalamus was stimulated, did not lead to thrusting or ejaculation even if the stimulation continued. The sites in the midbrain where the stimulation elicited touching and mounting were the ventral tegmental area, the substantia nigra, the nucleus reticularis mesencephali and the nucleus reticularis pontis oralis et caudalis. Touching and mounting were not elicited when the partner was put away from the male or replaced by submissive male monkeys or humans. The findings suggest that the stimulation-evoked touching and mounting are components of copulatory behavior and that the midbrain structures may be involved in the sexual behavior of male monkeys.

To elucidate the roles of glucose-sensitive (GS) and glucose-insensitive (GIS) cells of the lateral hypothalamic area (LHA), single neuron activity was recorded during 1) microelectrophoretic administration of chemicals, 2) a conditioned bar press feeding task, 3) gustatory, 4) olfactory, and 5) electrical brain stimulation. GS and GIS neurons showed different firing rate changes during phases of the task, and the responses were highly influenced by the palatability of the food and the motivational (hunger or satiety) state of the animal. The two groups of cells also differed in their responsiveness to gustatory and olfactory stimuli: GS neurons were more likely to respond to tastes and odors than GIS cells. Taste- and odor-responsive GS neurons were primarily suppressed by electrophoretically applied noradrenaline and were localized ventromedially within the LHA. The chemosensitive GIS cells, being organized along a dorsolateral axis, were especially excited by dopamine. The two sets of neurons had distinct connections with associative (orbitofrontal, prefrontal) cortical areas. GS and GIS cells, thus, appear to have differential and complex attributes in the control of feeding.

Intracellular recordings were made from neurons of the dorsomotor vagal nucleus (DMV) in slices of rat medulla oblongata. [D-Ala 2 , D-Leu 5 ]-enkephalin (DADLE), applied by perfusion (0.01–3 μM) or droplets, dose-dependently hyperpolarized 85% of the DMV neurons tested. The hyperpolarization, associated with a decrease in membrane resistance, persisted after elimination of synaptic activity by perfusion with Ca 2+ -free/high-Mg 2+ solution or with 1 μM TTX solution. The opioid antagonist, naloxone, reversibly inhibited DADLE-induced hyperpolarization. The hyperpolarization depended on extracellular K + concentration and reversed at about −90 mV. DADLE also decreased Ca 2+ -dependent spike duration and after-hyperpolarization (AHP). DAGO (a selective μ-receptor agonist), but not DPLPE (a selective δ-receptor agonist), mimicked DADLE's effects on membrane potential, Ca 2+ -dependent spike duration, and AHP. It is concluded that DADLE, through postsynaptic μ-type opioid receptors, hyperpolarized DMV neurons by increasing K + conductance, which may have an inhibitory effect on DMV output. DADLE-induced decrease of spike duration and AHP was also mediated by μ-receptors and could have additional effects on functions of the DMV neuron by virtue of reduction in Ca 2+ entry.

The involvement of a feeding-related endogenous sugar acid, 2-buten-4-olide (2-B4O) on central regulation of gastric acid secretion, and its antiulcer effects on several gastric and duodenal experimental ulcer models were investigated in rats. Spontaneous gastric acid secretion was not affected by 2-B4O at doses below 10 mg/kg. The peripheral secretagogue-stimulated gastric secretions were significantly increased by pretreatment with 2-B4O. Gastric acid secretion induced by 2-deoxy-D-glucose (2-DG) was significantly suppressed by pretreatment with 2-B4O at doses between 0.1 and 100 mg/kg. Gastric and duodenal ulcerations induced by cold stress plus indomethacin, restraint and water immersion stress, pylorus ligation or cysteamine were also inhibited by pretreatment with 2-B4O. The results suggest that antiulcer effects of 2-B4O are due to suppression of gastric acid secretion via reduction of activity of the vagus nerve and gastric-related hypothalamic neurons. Thus, 2-B4O may be useful for treatment of gastroduodenal ulcer.