Effects of temperature and melatonin on day-night expression patterns of arginine vasotocin and isotocin mRNA in the diencephalon of a temperate wrasse Halichoeres tenuispinis.

Most wrasses are protogynous species that swim to feed, reproduce during the daytime, and bury themselves under the sandy bottom at night. In temperate and subtropical wrasses, low temperature influences emergence from the sandy bottom in the morning, and induces a hibernation-like state in winter. We cloned and characterized the prohormone complementary DNAs (cDNAs) of arginine vasotocin (AVT) and isotocin (IT) in a temperate wrasse (Halichoeres tenuispinis) and examined the effects of day/night and temperature on their expression in the diencephalon, because these neurohypophysial peptides are related to the sex behavior of wrasses. The full-length cDNAs of pro-AVT and pro-IT were 938 base pairs (154 amino acids) and 759 base pairs (156 amino acids) in length, respectively. Both pro-peptides contained a signal sequence followed by the respective hormones and neurophysin connected by a Gly-Lys-Arg bridge. Reverse-transcription polymerase chain reaction (RT-PCR) revealed that pro-AVT mRNA expression was specifically observed in the diencephalon, whereas pro-IT mRNA expression was seen in the whole brain. Quantitative RT-PCR revealed that the mRNA abundance of pro-AVT and pro-IT was higher at midday (zeitgeber time 6; ZT6) than at midnight (ZT18) under 12 h light and 12 h darkness (LD 12:12) conditions, but not under constant light. Intraperitoneal injection of melatonin decreased the mRNA abundance of pro-AVT, but not of pro-IT. When fish were reared under LD 12:12 conditions at 25, 20, and 15 °C, day high and night low mRNA expressions of pro-AVT and pro-IT were maintained. A field survey revealed seasonal variation in the number of swimming fish at observatory sites; many fish emerged from the sandy bottom in summer, but not in winter, suggesting a hibernation-like state under the sandy bottom under low temperature conditions. We conclude that the day-night fluctuation of pro-AVT and pro-IT mRNA abundance in the brain is not affected by temperature and repeated under the sandy bottom in winter.

Noradrenergic modulation of gonadotrophin-inhibitory hormone gene expression in the brain of Japanese quail.

Gonadotrophin-inhibitory hormone (GnIH) is a hypothalamic neuropeptide that inhibits gonadotrophin synthesis and release in birds and mammals. In Japanese quail, GnIH neurones express the noradrenergic receptor and receive noradrenergic innervation. Treatment with noradrenaline (NA) stimulates GnIH release from diencephalic tissue blocks in vitro. However, the effects of NA on hypothalamic GnIH gene expression have not been determined. We investigated noradrenergic regulation of GnIH gene expression in the brain of male quail using the selective noradrenergic neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine hydrochloride (DSP-4). We first showed that DSP-4 reduced the number of noradrenergic (dopamine-ß-hydroxylase immunoreactive) cells in the locus coeruleus (LoC) and specifically lowered the NA concentration in the hypothalamus of male quail. Other monoamines, such as dopamine and serotonin, were not affected by drug treatment. DSP-4 did not decrease the numbers of noradrenergic cells of the lateral tegmental cell group, nor the plasma NA concentration. Decreased hypothalamic NA levels after DSP-4 treatment did not change GnIH gene expression in the brains of quail during their interaction with conspecifics. On the other hand, GnIH gene expression increased in the brains of quail socially isolated for 1 hour after DSP-4 treatment. These results suggest that some noradrenergic neurones have inhibitory effects on GnIH gene expression of the hypothalamus in solitary quail.

Extended neuroleptic administration modulates NMDA-R subunit immunoexpression in the rat neocortex and diencephalon.

BACKGROUND: This study aimed to evaluate the effect of extended olanzapine, clozapine and haloperidol administration on NMDA-R subunit immunoexpression in the rat neocortex and diencephalon. METHODS: To explore NR1, NR2A and NR2B subunit protein expression, densytometric analysis of immunohistochemically stained brain slices was performed. RESULTS: Interestingly, all neuroleptics caused a downregulation of NMDA-R subunit expression in the thalamus but increased the level of NR1 in the hypothalamus. Olanzapine upregulated hypothalamic NR2A expression, while clozapine and haloperidol decreased hypothalamic levels. We observed no significant changes in NR2B immunoreactivity. None of the studied medications had significant influence on NMDA-R subunit expression in the neocortex. CONCLUSIONS: Neuroleptic-induced reduction in the expression of thalamic NMDA-R subunits may play an important role in the regulation of glutamatergic transmission disorders in cortico-striato-thalamo-cortical loop in schizophrenia. A decrease in NMDA signaling in this region after long-term neuroleptic administration may also cautiously explain the incomplete effectiveness of these drugs in the therapy of schizophrenia-related cognitive disturbances.

Gonadotropin-releasing hormone stimulates the biosynthesis of pregnenolone sulfate and dehydroepiandrosterone sulfate in the hypothalamus.

The sulfated neurosteroids pregnenolone sulfate (Δ(5)PS) and dehydroepiandrosterone sulfate (DHEAS) are known to play a role in the control of reproductive behavior. In the frog Pelophylax ridibundus, the enzyme hydroxysteroid sulfotransferase (HST), responsible for the biosynthesis of Δ(5)PS and DHEAS, is expressed in the magnocellular nucleus and the anterior preoptic area, two hypothalamic regions that are richly innervated by GnRH1-containing fibers. This observation suggests that GnRH1 may regulate the formation of sulfated neurosteroids to control sexual activity. Double labeling of frog brain slices with HST and GnRH1 antibodies revealed that GnRH1-immunoreactive fibers are located in close vicinity of HST-positive neurons. The cDNAs encoding 3 GnRH receptors (designated riGnRHR-1, -2, and -3) were cloned from the frog brain. RT-PCR analyses revealed that riGnRHR-1 is strongly expressed in the hypothalamus and the pituitary whereas riGnRHR-2 and -3 are primarily expressed in the brain. In situ hybridization histochemistry indicated that GnRHR-1 and GnRHR-3 mRNAs are particularly abundant in preoptic area and magnocellular nucleus whereas the concentration of GnRHR-2 mRNA in these 2 nuclei is much lower. Pulse-chase experiments using tritiated Δ(5)P and DHEA as steroid precursors, and 3'-phosphoadenosine 5'-phosphosulfate as a sulfonate moiety donor, showed that GnRH1 stimulates, in a dose-dependent manner, the biosynthesis of Δ(5)PS and DHEAS in frog diencephalic explants. Because Δ(5)PS and DHEAS, like GnRH, stimulate sexual activity, our data strongly suggest that some of the behavioral effects of GnRH could be mediated via the modulation of sulfated neurosteroid production.

Kisspeptin expression in guinea pig hypothalamus: effects of 17ß-estradiol.

Kisspeptin is essential for reproductive functions in humans. As a model for the human we have used the female guinea pig, which has a long ovulatory cycle similar to that of primates. Initially, we cloned a guinea pig kisspeptin cDNA sequence and subsequently explored the distribution and 17ß-estradiol (E2) regulation of kisspeptin mRNA (Kiss1) and protein (kisspeptin) by using in situ hybridization, real-time PCR and immunocytochemistry. In ovariectomized females, Kiss1 neurons were scattered throughout the preoptic periventricular areas (PV), but the vast majority of Kiss1 neurons were localized in the arcuate nucleus (Arc). An E2 treatment that first inhibits (negative feedback) and then augments (positive feedback) serum luteinizing hormone (LH) increased Kiss1 mRNA density and number of cells expressing Kiss1 in the PV at both time points. Within the Arc, Kiss1 mRNA density was reduced at both time points. Quantitative real-time PCR confirmed the in situ hybridization results during positive feedback. E2 reduced the number of immunoreactive kisspeptin cells in the PV at both time points, perhaps an indication of increased release. Within the Arc, the kisspeptin immunoreactivity was decreased during negative feedback but increased during positive feedback. Therefore, it appears that in guinea pig both the PV and the Arc kisspeptin neurons act cooperatively to excite gonadotropin-releasing hormone (GnRH) neurons during positive feedback. We conclude that E2 regulation of negative and positive feedback may reflect a complex interaction of the kisspeptin circuitry, and both the PV and the Arc respond to hormone signals to encode excitation of GnRH neurons during the ovulatory cycle.

Characterization of antioxidant protection of cultured neural progenitor cells (NPC) against methylmercury (MeHg) toxicity.

Methylmercury (MeHg) is an environmental pollutant known to cause neurobehavioral defects and is especially toxic to the developing brain. With recent studies showing that fetal exposure to low-dose MeHg causes developmental abnormalities, it is therefore important to find ways to combat its effects as well as to clarify the mechanism(s) underlying MeHg toxicity. In the present study, the effects of MeHg on cultured neural progenitor cells (NPC) derived from mouse embryonic brain were investigated. We first confirmed the vulnerability of embryonic NPC to MeHg toxicity, NPC from the telencephalon were more sensitive to MeHg compared to those from the diencephalon. Buthionine sulfoximine (BSO) which is known to inhibit glutathione synthesis accelerated MeHg toxicity. Furthermore, antioxidants such as N-acetyl cysteine and alpha-tocopherol dramatically rescued the NPC from MeHg's toxic effects. Interestingly, a 12 hr delay in the addition of either antioxidant was still able to prevent the cells from undergoing cell death. Although it is now difficult to avoid MeHg exposure from our environment and contaminated foods, taking anti-oxidants from foods or supplements may prevent or diminish the toxicological effects of MeHg.

Sodium benzoate exposure downregulates the expression of tyrosine hydroxylase and dopamine transporter in dopaminergic neurons in developing zebrafish.

BACKGROUND: Recent data have demonstrated that treatment with sodium benzoate (SB) leads to significant developmental defects in motor neuron axons and neuromuscular junctions in zebrafish larvae, thereby implying that SB can be neurotoxic. This study examined whether SB affects the development of dopaminergic neurons in the zebrafish brain. METHODS: Zebrafish embryos were exposed to different concentrations of SB for various durations, during which the survival rates were recorded, the expression of tyrosine hydroxylase (TH) and dopamine transporter (DAT) in the neurons in the ventral diencephalon were detected by in situ hybridization and immunofluorescence, and the locomotor activity of larval zebrafish was measured. RESULTS: The survival rates were significantly decreased with the increase of duration and dose of SB-treatment. Compared to untreated clutch mates (untreated controls), treatment with SB significantly downregulated expression of TH and DAT in neurons in the ventral diencephalon of 3-day post-fertilization (dpf) zebrafish embryos in a dose-dependent manner. Furthermore, there was a marked decrease in locomotor activity in zebrafish larvae at 6dpf in response to SB treatment. CONCLUSIONS: The results suggest that SB exposure can cause significantly decreased survival rates of zebrafish embryos in a time- and dose-dependent manner and downregulated expression of TH and DAT in dopaminergic neurons in the zebrafish ventral diencephalon, which results in decreased locomotor activity of zebrafish larvae. This study may provide some important information for further elucidating the mechanism underlying SB-induced developmental neurotoxicity.

Blunted hippocampal, but not striatal, acetylcholine efflux parallels learning impairment in diencephalic-lesioned rats.

A rodent model of diencephalic amnesia, pyrithiamine-induced thiamine deficiency (PTD), was used to investigate the dynamic role of hippocampal and striatal acetylcholine (ACh) efflux across acquisition of a nonmatching-to-position (NMTP) T-maze task. Changes in ACh efflux were measured in rats at different time points in the acquisition curve of the task (early=day 1, middle=day 5, and late=day 10). Overall, the control group had higher accuracy scores than the PTD group in the latter sessions of NMTP training. During the three microdialysis sampling points, all animals displayed significant increases in ACh efflux in both hippocampus and striatum, while performing the task. However, on day 10, the PTD group showed a significant behavioral impairment that paralleled their blunted hippocampal--but not striatal--ACh efflux during maze training. The results support selective diencephalic-hippocampal dysfunction in the PTD model. This diencephalic-hippocampal interaction appears to be critical for successful episodic and spatial learning/memory.

Evidence for serotonin influencing the thalamic infiltration of mast cells in rat.

Serotonin (5-HT) is involved in neuroimmunomodulation. We analyzed the effects of sumatriptan, a 5-HT(1B/1D) receptor agonist, and ondansetron, a 5-HT(3) receptor antagonist, on thalamic mast cell (TMC) population, the only immunocytes known to infiltrate the brain in physiological conditions. Only sumatriptan was effective, significantly increasing TMC numbers versus controls, and especially those containing 5-HT. 5-HT(1B) receptors are concentrated in the median eminence on non-serotonergic axonal endings, probably hypothalamic terminal fibers, involved in hypothalamic-pituitary neuroendocrine modulating processes. TMC variations could reflect serotonergic actions on these fibers. TMCs would thus be cellular interfaces mediating immune action in the nervous system in relation with the hormonal status of the organism.

Neuropeptide Y inhibits the biosynthesis of sulfated neurosteroids in the hypothalamus through activation of Y(1) receptors.

We have recently shown that hydroxysteroid sulfotransferase (HST), the enzyme responsible for the biosynthesis of pregnenolone sulfate (Delta(5)PS) and dehydroepiandrosterone sulfate (DHEAS), is expressed in neurons located in the anterior preoptic area and the dorsal magnocellular nucleus of the frog diencephalon. As these two nuclei are richly innervated by NPY-immunoreactive fibers, we investigated the possible implication of NPY in the control of Delta(5)PS and DHEAS biosynthesis. Double labeling of frog brain sections revealed that 42% of the HST-immunoreactive perikarya in the diencephalon were contacted by NPY-containing fibers. In situ hybridization studies showed that Y(1) and Y(5) receptor mRNAs are expressed in the anterior preoptic area and the dorsal magnocellular nucleus. Pulse-chase experiments with (35)S-labeled 3'-phosphoadenosine 5'-phosphosulfate as a sulfate donor demonstrated that frog NPY (fNPY) inhibited the conversion of [(3)H]Delta(5)P and [(3)H]dehydroepiandrosterone ([(3)H]DHEA) into [(3)H,(35)S]Delta(5)PS and [(3)H,(35)S]DHEAS by diencephalic explants. The inhibitory effect of fNPY on Delta(5)PS and DHEAS formation was mimicked by (pPYY) and [Leu(31),Pro(34)]pNPY, which is an agonist for non-Y(2) receptors in mammals, and was completely suppressed by the Y(1) receptor antagonist BIBP3226. Conversely, the Y(2) receptor agonist pNPY-(13-36) and the Y(5) receptor agonist [D-Trp(32)]pNPY did not significantly modify the biosynthesis of [(3)H,(35)S]Delta(5)PS and [(3)H,(35)S]DHEAS. The present study provides the first evidence for the innervation of neurosteroid-producing neurons by NPY fibers. Our data also demonstrate that NPY, acting via Y(1) receptors, exerts an inhibitory effect on the biosynthesis of sulfated neurosteroids.

Interleukin-6 involvement in antidepressant action of Hypericum perforatum.

Hypericum, a plant widely used as antidepressant has been shown to interact with the immune system. We studied the effects of the administration of the Hypericum perforatum extract Ph-50, a Hypericum extract, standardized to flavonoids (50%) and containing 0.3% of hypericin and 4.5% of hyperforin in a forced swimming test and tryptophan, serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) diencephalic content using a high performance liquid chromatography method in male interleukin-6 (IL-6) knock-out (IL-6(-/-)) and wild type (IL-6(+/+)) mice. Hypericum extract (Ph-50; 500 mg/kg) oral acute administration reduced the immobility time of wild type, but not of knockout mice. Tryptophan content was not modified by Hypericum in all the animal groups. Serotonin and 5-HIAA diencephalic content was increased by Hypericum in both wild type and knockout mice. However, the increase observed in the wild type was greater than in knockout mice. These data indicate that IL-6 could be necessary to the antidepressant action of Hypericum, and that this cytokine (probably) mediates the effects of Hypericum through activation of the serotonin system.

Galanin/alpha2-adrenoceptor interactions in telencephalic and diencephalic regions of the rat.

The aim of this study was to evaluate whether galanin could affect central alpha2-adrenoceptors in telencephalic and diencephalic regions in the rat using quantitative receptor autoradiography with the alpha2 agonist radioligand [3H]p-aminoclonidine. Galanin 1 nM significantly and substantially increased the Kd value of the [3H]p-aminoclonidine binding sites in the medial hypothalamus and amygdala by 86% (p < 0.01) and 73% (p < 0.05) respectively. The Bmax value was only significantly increased with 3 nM galanin in the amygdala and the medial hypothalamus (both p < 0.05). The antagonist M35 counteracted the increase of the Kd values of the alpha2-adrenoceptor agonist binding sites produced by galanin 1 nM in the amygdala and the medial hypothalamus (both p < 0.001). These findings suggest the existence of an antagonistic galanin/alpha2 adrenoceptor interaction in the medial hypothalamus and amygdala that may be of relevance for alpha2-adrenoceptor-regulated neuroendocrine functions and food intake.

Systemic oxytocin treatment modulates alpha 2-adrenoceptors in telencephalic and diencephalic regions of the rat.

Systemic subchronic oxytocin treatment significantly and substantially increased the B(max) values of the alpha 2 agonist [(3)H]UK14.304 binding sites in the hypothalamus, the amygdala and the paraventricular thalamic nucleus of the rat as shown by quantitative receptor autoradiography. These results suggest that long-term modulation of autonomic and neuroendocrine functions and emotional behaviours elicited by brain oxytocin may involve enhancement of central alpha 2-adrenoceptor function.

Effect of amphetamine on the expression of the metabotropic glutamate receptor 5 mRNA in developing rat brain.

Mechanisms underlying the acute effects of amphetamine (AMP) were examined by monitoring the expression of metabotropic glutamate receptor 5 (mGluR5) and specific 3H-glutamate binding in the developing rat brain. Each of the postnatal day (P) 4, P21 and P60 rats received one intraperitoneal injection of AMP, 5 mg/kg or saline and were sacrificed one hour later. In situ hybridization analysis revealed that the AMP treatment raised the levels of the mGluR5 mRNA by 9-28% in the neurons of the layer 5 of motor and somatosensory cortices, whereas reduced the levels by 12-28% in the layer 5 of perirhinal cortex and the ventromedial part of caudate-putamen of the 3 ages. In the layer 2/3 neurons of cingular cortex, an 18% higher and 14% and 22% lower than control levels of the mRNA were detected in the P4 and in the P21 and P60 rats injected with AMP. Moreover, the levels of mGluR5 mRNA in the hippocampi and dentate gyri were elevated by AMP to 110-151% of controls in the rats of 3 ages. Reversible 3H-glutamate binding assay showed an increase of 25% and a 12% decrease in the binding levels in the cortices of AMP-treated P4 and P21 rats. The AMP administration also produced a 27% reduction and 62% elevation in the binding of the hippocampi of P4 and P60 rats. The results reveal age- and region-dependent changes in the expression of the glutamate receptors induced by AMP and may indicate differential plastic capability of the neurons to the drug perturbation.

Effects of Hypericum perforatum on levels of 5-hydroxytryptamine, noradrenaline and dopamine in the cortex, diencephalon and brainstem of the rat.

The plant Hypericum perforatum is used in folk medicine to treat several diseases and research attention has been recently focused on its antidepressant action. Hypericin and flavonoids are the most important constituents of the plant, but the exact role of these compounds in the effects of hypericum on mood disorders is not well known. We have investigated the contribution of these compounds to the antidepressant effects of hypericum. The effects of acute administration of hypericum extracts on levels of 5-hydroxytryptamine (5-HT), tryptophan, 5-hydroxyindoleacetic acid (5-HIAA), noradrenaline and dopamine in the cortex, diencephalon and brainstem was evaluated. The levels of these neurotransmitters were measured 1 h and 24 h after administration of two different extracts, one containing 0.3% hypericin and 6% flavonoids (Li 160; 25-500 mgkg(-1)), the other containing 0.3% hypericin and 50% flavonoids (Ph-50; 25-500 mgkg(-1)). Results from experiments performed on 5-HT turnover were compared with the effects of fluoxetine (10-80 mgkg(-1)). Li 160, Ph-50 and fluoxetine induced a significant increase in the 5-HT content of the cortex. In the diencephalon Ph-50, but not Li 160 or fluoxetine, elicited an increase in 5-HT and 5-HIAA levels. In the brainstem Ph-50 and fluoxetine caused an increase in 5-HT content; Li 160 did not change neurotransmitter content. Both Li 160 and Ph-50 caused increases of noradrenaline and dopamine in the diencephalon. In the brainstem only Ph-50 induced an increase in noradrenaline content. Our data confirm that acute administration of hypericum extracts modifies the levels of neurotransmitters involved in the pathophysiology of mood disorders. When the extracts contain a higher concentration of flavonoids the effects are more widespread and involve brain regions such as diencephalon and brainstem that are implicated in depression.

Region specific expression of NMDA receptor NR1 subunit mRNA in hypothalamus and pons following chronic morphine treatment.

The NMDA receptor has been implicated in opioid tolerance and physical dependence. Using in situ hybridization techniques, the effects of chronic morphine treatment on the expression of mRNAs encoding the NMDA receptor subunits NRI, NR2A, and NR2B were investigated. A significant increase in the level of the NR1 subunit mRNA was found in the locus coeruleus and the hypothalamic paraventricular nucleus following 3 days of intracerebroventricular (i.c.v.) morphine infusion (26 nmol microl(-1) h(-1)) through osmotic minipumps. No changes were detected in expression of the NRI mRNA in the frontal cortex, caudate-putamen, nucleus accumbens, amygdala, CA1, CA2, and the dentate gyrus of the hippocampus, and in the central grey after morphine treatment. The expression of NR2A and NR2B subunit mRNAs did not change after morphine treatment in any brain region. These results suggest that changes in gene expression of the NRI subunit of the NMDA receptor are involved in the development of morphine tolerance and dependence.

Modification of gonadotropin releasing hormone (GnRH) mRNA expression in the retinal-recipient Thalamus.

Although the environmental cues that trigger reproductive behaviors are known for many species, the mechanisms through which these signals influence the neurochemistry of the brain to produce behavior have been elusive. In this study, we describe a retinally modulated system of gonadotropin releasing hormone (GnRH) producing neurons in the thalamus of the plainfin midshipman fish, Porichthys notatus. Previously, we cloned and sequenced the cDNA for prepro-GnRH in midshipman. Here, using in situ hybridization, we localized prepro-GnRH mRNA to the ventrolateral nucleus of the thalamus, three divisions of the preoptic area, the ganglion of the terminal nerve, and the olfactory bulb. Since the thalamus, terminal nerve ganglion, and preoptic area have been associated with visual functions, we investigated the retinal connections in midshipman. In particular, biocytin tract tracing delineated a reciprocal connection between the ventrolateral nucleus of the thalamus and the retina. Retinofugal projections are exclusively contralateral. Experimental manipulation of this retinalthalamic loop through complete optic nerve transection shows that GnRH mRNA expression in the contralateral ventrolateral nucleus may be influenced by the retina. We hypothesize that a reciprocal retinothalamic GnRH circuit is important in modulating the expression of seasonal reproductive behaviors.

Effect of morphine on hypothalamic tyrosine hydroxylase mRNA levels in dopaminergic neurons and on preoptic DOPAC levels measured by microdialysis.

Morphine not only suppresses norepinephrine-induced increases in LHRH mRNA levels but, in these same animals, it simultaneously amplifies norepinephrine (NE)-induced LH release. These observations suggest that NE may activate parallel mechanisms which independently increase LHRH mRNA levels and LHRH release and suggest that some of these effects could be mediated indirectly via morphine's action on different components of the hypothalamic dopamine (DA) system. Accordingly, in the present studies we examined the effects of morphine on various components of this dopamine system using as our index of altered DA neuronal activity, the changes which occur in tyrosine hydroxylase (TH) mRNA levels following morphine. As an ancillary index of changes which occur in dopamine neuronal activity, we measured, by microdialysis, the changes which occur in preoptic dihydroxyphenylacetic acid (DOPAC) levels after either subcutaneous injections or following microinfusions of morphine into the zona incerta (ZI). In a final study, we evaluated whether DA when given alone (icv infusion) or prior to icv NE would altered LH release. Single cell levels of TH mRNA in preoptic A15 and periventricular anterior hypothalamic A14 DA neurons were not affected by morphine 1, 5 and 24 h later. In contrast, within 1 h after morphine, TH mRNA levels in ZI A13 neurons were significantly elevated and they remained high at 5 nd 24 h compared to controls. Morphine also resulted in a significant rise in TH mRNA levels in tuberoinfundibular DA neurons (TIDA) (A12) within 1 h and these levels remained high to 5 h. Thereafter, by 24 h, message levels had returned to control values. Morphine also resulted in a rapid rise in plasma prolactin (Prl) with peak values occurring at 20 min and then returning to baseline by 90 min. When morphine was given sc it resulted, within 15 min, in a rapid rise in preoptic DOPAC levels and these levels continued to rise such that they were 217% higher than pretreatment values by 105 min. Preoptic 5-hydroxyindoleacetic acid (5-HIAA) levels also increased by 25-75% after sc morphine. The microinfusion of morphine into ZI also resulted in elevated preoptic DOPAC but not 5-HIAA levels within 15 min. The icv infusion of DA alone had no effect on plasma LH whereas, NE (icv) produced a modest but significant increase in plasma LH. When DA was given 15 min prior to the infusion of NE, neither amplification nor inhibition of NE-induced LH release occurred. From these and other studies we conclude that the morphine-induced suppression of TIDA neuronal activity may allow NE to release greater amounts of LHRH from axon terminals in the median eminence.(ABSTRACT TRUNCATED AT 400 WORDS)

AMPA/kainic acid glutamate receptor antagonism in the zona incerta dorsal to the subthalamic nucleus inhibits amphetamine-induced stereotypy bur not locomotor activity.

The effect of 6,7-dinitroquinoxaline-2,3-dione (DNQX), an alpha-amino-3- hydroxy-5-methyl-4-isoxazole-propionate (AMPA)/kainic acid glutamate receptor antagonist, injected into the zona incerta (ZI) was investigated to determine whether the behavioral responses to systemic amphetamine involve AMPA/kainic acid receptors in this brain region. Rats were injected bilaterally in the ZI with either vehicle or DNQX (1 microgram/0.5 microliter) and immediately given a systemic injection of D-amphetamine (0.5, 1.0 or 10.0 mg/kg, s.c.). Locomotor activity was recorded for 1 h. DNQX did not significantly affect hypermotility stimulated with 0.5 and 1.0 mg/kg amphetamine, but markedly increased the level of locomotor activity elicited by the higher dose, 10 mg/kg. To test the hypothesis that the enhanced locomotor response to high dose amphetamine was due to an inhibition of stereotyped behavior, the effect of DNQX in the ZI on amphetamine and apomorphine-induced stereotypy was investigated. DNQX significantly inhibited stereotypy induced by amphetamine (10 mg/kg) and apomorphine (1 mg/kg), with the onset of inhibition of amphetamine-induced stereotypy corresponding to the onset of enhanced locomotor activity. Ibotenic acid lesions of the ZI produced similar results, having an insignificant effect on locomotor activity stimulated by low dose amphetamine (1 mg/kg) and an attenuation of apomorphine-induced stereotypy which was of a magnitude comparable to that produced by DNQX. Thus, the AMPA/kainic acid subtypes of glutamate receptors in the ZI may be involved in the regulation of motor function mediated via striatal output but not mesolimbically generated locomotor activity.

Neuropeptide Y and food intake in fasted rats: effect of naloxone and site of action.

Central administration of neuropeptide Y (NPY) induces food intake in freely feeding animals and this effect is mediated by hypothalamic sites. Little is known, however, about the effect of NPY on food intake and site of action in food-deprived animals. To examine this further, 24-h fasted rats received injections of saline or NPY into the lateral cerebral ventricle (10 micrograms/10 microliters; n = 8) or into the lateral (LH) or ventromedial hypothalamus (VMH) (1 microgram/0.5 microliters; n = 44). In addition, intracerebroventricular (i.c.v.) injections of NPY were carried out with or without i.c.v. naloxone (25 micrograms), a specific opioid receptor antagonist. During the first 40 min food intake was not different with or without NPY. After 60 and 120 min, food intake was 5.9 +/- 0.4 g and 8.3 +/- 0.6 g with i.c.v. saline which was significantly augmented by i.c.v. NPY to 8.7 +/- 0.9 g and 14.4 +/- 1.5 g, respectively (P less than 0.05). This increase in food consumption was due to a prolongation of feeding time. The opioid receptor antagonist naloxone significantly augmented latency to feed, both in the absence and presence of NPY (8.0 vs 1.7 min or 14.7 vs 2.8 min, respectively) and abolished the NPY-induced increase in food intake. Following intrahypothalamic injection of NPY, an increase in food intake (greater than 20%) was observed in 50% of the histologically identified LH and VMH sites, but only in 15% of the injection sites outside the LH/VMH.(ABSTRACT TRUNCATED AT 250 WORDS)