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Chronic nicotine administration has long been known to increase the number of high-affinity alpha4beta2 nicotinic receptors with lesser effects on low-affinity alpha7 nicotinic receptors. Nicotine has been shown to promote the release of a variety of neurotransmitters including glutamate. Nicotine may also interact directly with the glutamatergic receptors. Nicotinic-glutamate interactions may be critical to the long-term effects of nicotine. Conversely, glutamatergic drugs may interact with the nicotinic system. Such interactions have important implications in interpretation of the mechanism of drug actions, especially when the drugs are given together. The current study examined the effects of chronic administration of nicotine (5 mg of the nicotine base/kg/day for 28 days), dizocilpine (MK-801) (0.3 mg/kg/day for 28 days), an NMDA receptor antagonist, as well as the combination of the two drugs on nicotinic and NMDA receptor densities in discrete brain regions. The chronic dose of dizocilpine used was behaviorally active causing a dramatic reduction in prepulse inhibition (PPI) of acoustic startle response. The nicotine dose used did not significantly affect PPI but previously we have found it to be behaviorally active in improving working memory function. High-affinity nicotinic receptor binding, as has been seen previously, was significantly increased by chronic nicotine in most areas. Chronic dizocilpine alone did not affect high-affinity nicotinic receptor binding, but it did modify the effects of chronic nicotine, attenuating nicotine-induced increases in the frontal cortex and striatum. Low-affinity nicotinic binding was significantly increased by chronic nicotine in only one area, the cerebellum. Chronic dizocilpine significantly increased low-affinity nicotinic binding in several brain areas, the colliculi, hippocampus, and the hypothalamus. The combination of nicotine and dizocilpine attenuated the effects of each with diminished nicotine-induced increased nicotinic low-affinity binding in the cerebellum and diminished dizocilpine-induced increased nicotinic low-affinity binding in the hippocampus and hypothalamus. In contrast, chronic nicotine and dizocilpine had a mutually potentiating effect of increasing nicotinic low-affinity binding in the frontal cortex. NMDA receptor binding was affected only in the hippocampus, where both dizocilpine and nicotine significantly increased binding. Chronic nicotine effects on receptor regulation are significantly affected by concurrent blockade of NMDA glutamate receptors.

The structural basis for depressive disorders remains unknown. Studies using neuroimaging and postmortem brain tissue indicate that anatomic substrates may contribute to major depression disorder (MDD) and bipolar disorder (BD). The present study used design-based stereology to assess neuron loss in 2 well-defined hypothalamic structures, the paraventricular nucleus (PVN) and supraoptic nucleus (SON), in clinically well-studied cases with severe depression. The left or right diencephalon was blocked from 26 brains removed at autopsy from age-matched controls (5 male/3 female) and patients with MDD (6 male/5 female) and BD (5 male/2 female). Serial sections were cut at an instrument setting of 60 microm through the entire PVN and SON from left hypothalamus and 8 to 10 sections per brain were systematic-random sampled and stained with cresyl violet. A trained operator blind to clinical diagnosis used computerized stereology to estimate total neuron numbers in PVN and SON. The results revealed a selective, robust reduction of approximately 50% in total neuron number in the PVN for major depression and bipolar cases compared with age-matched controls, with no differences in neuron numbers in the SON. This selective neuronal loss in the PVN appears to identify an important neurobiologic substrate for the behavioral manifestations of depression.

Nicotine's counteraction of adverse effects of ethanol on cognitive function and motor coordination may play a major role in the observed high incidence of smoking among alcoholics. Previously, we have observed protective effects of nicotine against ethanol-induced neurotoxicity in cultured cortical and cerebellar granule cells as determined by lactate dehydrogenase assay. Ethanol-induced apoptosis may be a contributory mechanism to its neuronal toxicity. In this study we sought to determine whether ethanol induces formation of caspase 3 (reflective of apoptosis) in these cells and whether these effects may be blocked by nicotine pretreatment. Primary cultures of cerebral cortical and cerebellar granule cells were prepared from the brains of 20 day old Sprague-Dawley fetuses. Exposure of cells to ethanol (10-100 mM) for 3 days resulted in a dose-dependent increase in caspase 3 activity and cytotoxicity. Pretreatment with nicotine (5-20 microM) dose dependently attenuated these effects of ethanol. Complete block of ethanol effects was achieved by the highest dose of nicotine (20 microM). Nicotine, at concentrations administered, did not affect caspase activity or neuronal viability. These results suggest that at least some of the neurotoxic effects of ethanol may be mediated by apoptosis and that pretreatment with nicotine can prevent these effects of ethanol. Anti-apoptotic effects of nicotine in this model may be suggestive of potential use of nicotinic agonists in neurotoxic insults and/or neurodegenerative disorders.

Affective disorders often occur in combination with disrupted sleep-wake cycles and abnormal fluctuations in hypothalamic neurotransmitters. Hypocretin (orexin) is a hypothalamic neuropeptide linked to narcolepsy, a sleep-related disorder characterized by profound disturbances in the normal sleeping pattern and variable degrees of depression. Wistar-Kyoto (WKY) rats exhibit depressive characteristics and patterns of sleep disruption similar to that observed in depressed human patients. In this study we sought to determine whether the total number or the size of hypothalamic hypocretin neurons in WKY rats differ from their control, Wistar (WIS) rats. Immunocytochemical and stereological methods were applied to quantify hypocretin-1 containing neurons in the hypothalamus. The study revealed 18% fewer hypocretin-1 positive neurons as well as a 15% decrease in average neuronal soma size of hypocretin-1 producing cells in the hypothalamus of WKY rats compared to WIS rats. These findings support the view that reduced number or size of hypothalamic hypocretinergic neurons may underlie the disrupted sleep pattern associated with depressive characteristics in WKY rats.

The high incidence of smoking among alcoholics may be partially due to nicotine's ability to counteract some of the adverse effects of ethanol on motor coordination and/or cognitive functions. Neuroprotective effects of nicotine on ethanol-induced toxicity in cerebellar granular cells have been observed. In this study, we sought to determine whether similar protection is observed in neocortical cells and if so, what specific nicotinic receptor subtypes may be mediating the actions of nicotine. Primary cultures of neocortical cells were prepared from 20-day embryos obtained from time-pregnant Sprague-Dawley rats. Cells were cultured for 10 days and were then exposed for 3 days to various concentrations of ethanol with and without pretreatment with nicotine and nicotinic antagonists. Cellular toxicity was evaluated by measuring the lactate dehydrogenase level. Administration of ethanol (10-100 mM) resulted in a dose-dependent toxicity. Pretreatment with nicotine 5-20 microM resulted in a dose-dependent protection against ethanol-induced toxicity. The effects of nicotine were blocked by pretreatment with nicotinic antagonists such as mecamylamine (1-20 microM), dihydro-beta-erythroidine (DHBE) 50 nM-1.0 microM and methyllycaconitine (MLA) 5 nM-1 microM in a dose-dependent manner. Compared to previous studies, higher ethanol concentrations were required to induce toxicity in neocortical vs cerebellar granule cells. Moreover, the effects of nicotine in the neocortical cells were blocked by lower concentrations of MLA, but higher concentrations of DHBE compared to cerebellar cells. Collectively, the results suggest differential sensitivity of various neuronal populations to the toxic effect of ethanol. Furthermore, protective effects of nicotine against alcohol in various regions appear to be mediated by different nicotinic receptor subtypes. The neuroprotective effect of nicotine against ethanol-induced toxicity may be a contributing factor to the high incidence of smoking among alcoholics.

Tourette syndrome (TS) is a neurological disorder characterized by persistent motor and phonic tics. Administration of the selective 5-HT(2A/2C) agonist 1-(2, 5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) induces head twitches in mice that have been proposed to model tics seen in TS. Previous studies have demonstrated that nicotine markedly attenuates DOI-induced head twitch response (HTR). This and the reports that nicotine may have clinical efficacy in reducing symptoms of TS suggest possible involvement of the nicotinic cholinergic system in this disorder. Donepezil is an acetylcholinesterase inhibitor approved for use in mild to moderate Alzheimer's disease. The purpose of this study was to investigate whether donepezil might also reduce DOI-induced HTR, and whether its combination with nicotine might result in an additive or synergistic effect. Moreover, to elucidate the possible role of nicotinic receptors in this paradigm, the effects of mecamylamine, a nicotinic antagonist, was also evaluated. Acute and chronic administration of donepezil (0.1 mg/kg) or nicotine (0.5 mg/kg base), significantly reduced DOI-induced HTR. No additive or synergistic effects of donepezil and nicotine were observed. Acute mecamylamine administration (0.5-5.0 mg/kg) dose-dependently inhibited DOI-induced HTR. None of the mecamylamine doses blocked the inhibitory effects of donepezil or nicotine on DOI-induced HTR. These results suggest that donepezil may have therapeutic potential in treating motor tic symptoms of TS. Moreover, the action of donepezil and nicotine may be mediated through the same mechanism.

Alcoholism is associated with a higher incidence of smoking. In addition to the stimulatory effects of both ethanol and nicotine on the mesolimbic reward pathway, nicotine's ability to counteract some of the adverse effects of ethanol (e.g. ataxia) may be a powerful incentive for alcohol consumers to increase their tobacco (nicotine) intake. The cerebellum is believed to play an important role in ethanol-induced ataxia. In this study, we sought to test the hypothesis that nicotine would protect against toxic effects of ethanol in primary cultures of cerebellar granule cells. Moreover, it was postulated that the effects of nicotine would be mediated through nicotinic receptors. Primary cultures of cerebellar granule cells were prepared from 20-day embryos obtained from timed-pregnant Sprague Dawley rats. Cells were cultured for 10 days and were then exposed for 3 days to various concentrations of ethanol with and without pretreatment with nicotine and nicotinic antagonists. Cellular toxicity was evaluated by measuring the lactate dehydrogenase level. Administration of ethanol (10-100 mM) resulted in a dose-dependent toxicity. Pretreatment with nicotine 1-20 micro M resulted in a dose-dependent protection against ethanol-induced toxicity. The effects of nicotine were blocked by pretreatment with nicotinic antagonists such as mecamylamine 1-20 micro M, dihydro-beta-erythroidine 1.0 nM-1.0 micro M and methyllycaconitine 5 nM-5 micro M in a dose-dependent manner. Thus, ethanol-induced cytotoxicity in primary cultures of cerebellar granule cells is blocked by pretreatment with nicotine. The effects of nicotine, in turn, may be blocked by nicotinic antagonists, implicating both high and low affinity nicotinic receptors in mediating the actions of nicotine. The exact mechanism of ethanol-induced toxicity and/or neuroprotection through activation of nicotinic receptors in this paradigm remains to be elucidated. The neuroprotective effect of nicotine against ethanol-induced toxicity in cerebellar neurons may be a contributing factor to the high incidence of smoking among alcoholics.

Background: Alcoholism is associated with a higher incidence of smoking. The mesolimbic dopaminergic pathway is believed to play an important role in the reinforcing effects of both ethanol and nicotine. This study was undertaken to determine whether simultaneous administration of systemic ethanol and microinjection of nicotine into the ventral tegmental area (VTA) would result in exaggerated release of dopamine (DA) in the shell region of nucleus accumbens., Methods: Microdialysis was applied in awake, freely moving adult male Wistar rats, and DA concentration in the dialysate was measured by HPLC-electrochemical detectors., Results: Systemic administration of ethanol or microinjection of nicotine into VTA resulted in a dose-dependent increase in DA release (extracellular DA concentration). Simultaneous administration of lower doses of nicotine and ethanol resulted in an additive effect on the released DA. This additive effect was not observed with higher doses of nicotine and ethanol. Administration of the nicotinic antagonist mecamylamine into VTA completely blocked ethanol-induced DA release., Conclusions: These data support the hypothesis that the reinforcing effects of ethanol are at least partially mediated through the nicotinic receptors in the VTA. Furthermore, administration of selective nicotinic antagonists may be of therapeutic potential in reducing the rewarding effects of ethanol. The data also suggest that the combined effects of ethanol and nicotine on the "reward pathway" may be a contributing factor to the high incidence of smoking in alcoholics.

Background: Rats treated chronically in a large, open field with the dopamine D2/D3 receptor agonist quinpirole (QNP) develop compulsive checking behavior as defined by a set of behavioral criteria. This paradigm has been suggested as an animal model of obsessive-compulsive disorder (OCD). Because nicotine blocks various behaviors induced by ontogenetic QNP administration, we asked whether nicotine could attenuate QNP-induced compulsive checking., Methods: Adult male Long-Evans rats (n = 14/group) were treated twice weekly with saline (control), or with QNP (0.5 mg/kg) for 14-16 injections. On the last two injections, rats were pretreated in random order with an acute dose of nicotine (0.3 mg/kg base) or saline 10 min before administration of QNP or saline; and the effects on checking behavior was examined. The effects of chronic QNP treatment on nicotinic receptors in discrete brain regions were also determined., Results: Chronic QNP resulted in compulsive checking and increases in cerebellar alpha4beta2 and alpha7 nicotinic receptor densities. Nicotine pretreatment significantly reduced one of the three measures of compulsive checking behavior., Conclusions: Nicotine attenuates some symptoms of compulsive checking in a rat model of OCD; however, the mechanisms of this effect and therapeutic efficacy of nicotinic agonists in OCD require further study.

Maternal smoking during pregnancy or in utero exposure of the fetus to nicotine may result in learning difficulties and hyperactivity in the child. To elucidate possible involvement of the alpha(7) nicotinic receptor subtype in these behavioral impairments, pregnant dams were treated with nicotine (9 mg/kg/day) via osmotic minipumps throughout gestation. Male offspring were weaned at postnatal day 18, and were tested for locomotor activity at postnatal days 20-24. Pups were sacrificed on postnatal day 36-38 and 18 discrete brain areas were analyzed for [125I]alpha-bungarotoxin (alpha-BT) binding by quantitative autoradiography. Prenatal nicotine caused an elevation in locomotor activity (vertical movements) in offspring. [125I]alpha-BT binding was significantly reduced in the hippocampal CA1 region (29%), dentate gyrus (22%), and medial geniculate nucleus (29%). These findings suggest that some of the behavioral abnormalities induced by prenatal nicotine exposure may be due to a reduction of alpha(7) nicotinic receptors in discrete brain regions.

The adaptive response of the neuroendocrine system to stress is known to be impaired during ageing, and this impairment may be genetically determined. To elucidate further the effect of genotype, inbred male rats of the Wistar-Kyoto (WKY) strain, characterized by their hyper-reactivity to stressors and shorter life span, were compared with Brown-Norway (BN) rats. In young BN rats, resting prolactin concentrations were lower than in WKY animals and were reduced with age, while in WKY rats they remained unchanged with age. In young rats of both strains prolactin concentrations were highest after subjecting them to stressful stimuli for 15 min. After 2 h of restraint stress (during which the animals were confined to a narrow space that restricted movement) prolactin concentrations in young rats returned to pre-stress values, while remaining high in aged rats of both strains. Concentrations of corticotrophin (or adrenocorticotrophic hormone, ACTH) were lower in BN than in WKY rats and did not change with age in either strain. After 2 h of stress, ACTH concentrations were still slightly higher than normal in both young and aged BN rats, but not in WKY rats. Corticosterone concentrations were similar in young WKY and BN rats and were reduced in aged rats of both strains. After 2 h of stress, corticosterone concentrations were still high in aged, but not in young rats of both strains. However, this stress-induced increase was larger (3.7 times as much) in the BN strain than in the WKY strain (in which the increase was 1.7 times as much). The concentrations of hypothalamic monoamines were similar in young rats of both strains, although stress resulted in reduced noradrenaline concentrations, as previously documented, and in minor increases in 3,4-dihydroxyphenylacetic acid in both strains. During ageing, basal noradrenaline concentrations were reduced only in WKY rats, while the amount of 5-HT increased selectively in BN rats. Concentrations of 5-hydroxyindoleacetic acid were increased after stress in aged WKY rats only. The results demonstrate that resting plasma concentrations of the stress hormones ACTH and corticosterone and of prolactin are lower in BN than in WKY rats. In ageing, however, the stress-induced increases in the concentrations of these hormones are relatively higher in the BN strain, which is characterized by a longer life span.(ABSTRACT TRUNCATED AT 400 WORDS)

The responses of the hypothalamic-pituitary-adrenal axis during chronic stress are characterized by normal or slightly elevated plasma ACTH, increased hypothalamic corticotropin-releasing hormone (CRH) and vasopressin secretion, decreased pituitary CRH receptors and hypersensitivity of the ACTH and glucocorticoid responses to a novel stress. To determine the role of CRH and vasopressin in the pituitary hyperresponsiveness to a superimposed stress, pituitary CRH receptors and plasma ACTH responses were measured in rats receiving minipump infusions of CRH or a combination of CRH and vasopressin (VP), 50 ng/min of each for 50 h. Rats were killed by decapitation with or without exposure to ether vapor for 5 min or immobilization for 15 or 30 min, and blood was collected for ACTH and corticosterone determinations. The pituitary CRH receptor concentration measured by binding 125I-Tyr-oCRH, was reduced by 45 and 80% in CRH- and CRH-plus-VP-infused rats, respectively, with no changes in receptor affinity. Acute stress by ether exposure or immobilization had no effect on pituitary CRH receptors. Adrenal weight was significantly increased, and thymus weight decreased in CRH-infused animals, indicating activation of the pituitary adrenal axis. However, in contrast to the responses following chronic stress, the increases in plasma ACTH in response to an injection of 10 micrograms/kg CRH or acute stress were significantly lower in CRH- and CRH-plus-VP-infused rats. Furthermore the content and release of ACTH from quartered pituitaries were also decreased in chronically treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Corticotropin-releasing hormone (CRH), in addition to its neuroendocrine role, may act as a central neurotransmitter. Cerebral cortical CRH may have an important role in behavioral and neurodegenerative disorders. To gain an understanding of factors that may influence cortical CRH, we investigated the effect of several neurotransmitters and neuropeptides on the release of immunoreactive CRH (iCRH) from various cerebral cortical regions [frontal (FC), parietal (PC), temporal (TC), and occipital (OC)] in vitro. The hypothalamic release of iCRH was also evaluated under the same experimental conditions. Basal release of iCRH was approximately 2-fold, and KCl-stimulated iCRH release was approximately 4-fold higher in the hypothalamus than in any of the cortical regions. Cortical iCRH release was stimulated by 10 nM somatostatin (SRIF) in PC and 1 nM neuropeptide Y (NPY) in TC. Cortical iCRH release was inhibited by 1 and 10 nM acetylcholine (ACh), 0.1 microM glutamate, and 10 nM NPY. These effects were confined to the FC and/or PC. Hypothalamic iCRH release was stimulated by 1 and 10 nM ACh, 10 microM GABA, and 1 and 10 nM serotonin but was inhibited by 10 nM SRIF and 1 microM GABA. Growth hormone-releasing hormone did not affect cortical or hypothalamic iCRH release. These results demonstrate that CRH release from the cerebral cortex and the hypothalamus are under different regulatory mechanism(s). Furthermore, they indicate that the release of CRH in various cortical regions may be regulated differentially by the same neurotransmitter.

Open field behavior and age-related changes in anterior pituitary corticotropin-releasing hormone (CRH) receptors, as well as plasma ACTH levels, were measured in two inbred rat strains. The strains utilized were Wistar Kyoto (WKY) and Brown-Norway (BN), the former characterized by shorter life-span and hyper-reactivity to stressors as compared to the latter. Behaviorally, WKY rats showed hyper-responsivity to a novel environment as indicated by their delay in entering the open field, increased grooming, reduced rearing, and reduced locomotion. These strain-dependent behavioral differences were not affected by aging. The binding capacity of CRH receptors was similar in both strains and Bmax values were decreased (25-27%) with aging, with no changes in Kd values. In contrast, plasma ACTH levels were 67% higher in WKY than in BN rats but did not change with aging. Thus, despite pituitary CRH receptor down regulation, plasma ACTH levels following decapitation were sustained during aging. This suggests the presence of some compensatory factors in the hypothalamic-pituitary axis regulation which sustain ACTH response during aging. Furthermore, the findings indicate that higher plasma ACTH levels and hyper-reactivity to a novel environment are inversely correlated with longevity in the rat.

To determine the source of glutamatergic input to the septum and to the nucleus accumbens septi, glutamate uptake was assessed after transections of the frontal cortex and/or fornix. Uptake in the septum and accumbens was reduced by 25 and 30% respectively, 6 days after bilateral frontal cortex transections. Both indices returned to control levels 30 days postoperatively. In contrast, while unilateral fornix transection did not affect uptake in the accumbens at either day 6 or 30, uptake in the septum was significantly reduced (25-35%) at both times. When a unilateral transection of the fornix was performed in rats with a pre-existing bilateral ablation of the frontal cortex, a further reduction in uptake was observed in the septum (50-60% at both 6 and 30 days after the fornix transection). The data implicate glutamate as a neurotransmitter in frontocortico-septal projections and suggest that the contribution of the hippocampo-septal system to total glutamate uptake in the septum is increased following ablation of the frontocortico-septal system.

The study describes stress-induced changes in high-affinity uptake and release of glutamate by synaptosomal preparations from several regions of rat brain. The results demonstrate that restraint stress can lead to increased glutamate uptake and release in limbic forebrain regions (frontal cortex, hippocampus and septum) but not in the striatum. The increase in glutamate uptake was evident after 30 min of stress. A plateau (140-150% of unhandled controls) was reached after 1 h and was maintained after 4 h of continuous stress. The stress-induced increase in glutamate uptake was observed with glutamate concentrations of up to 10 microM, but not with 500 microM. the results indicate that forebrain glutamatergic terminals are activated by stressful stimuli in a regionally selective manner, and suggest that enhanced high-affinity uptake is important in clearing increased levels of released glutamate.

Stress induced changes in neurochemical indices of neurotransmission are more pronounced in the septohippocampal cholinergic system of Wistar Kyoto rats, which are behaviorally more reactive to stressors and have a shorter life span, than in Brown Norway rats. Moreover, pronounced degeneration of septohippocampal cholinergic neurons occurs earlier in life in Wistar Kyoto rats. In the present study the high affinity synaptosomal uptakes of choline and glutamate were used as indices for cholinergic and glutamatergic systems respectively. Following 2 hr of mild restrain stress increases in both uptake systems were observed in all regions examined (hippocampus, septum and frontal cortex). The stress-induced increases were generally similar in young (3 months) and aged (20 months) rats of both strains. The noted exception was that choline uptake levels, which were reduced in the hippocampus of unhandled aged WKY rats, remained unchanged after stress. The results confirm the involvement of the septohippocampal cholinergic system in the response to acute stress and extend the findings to include the hippocamposeptal glutamatergic system activation as well. It is suggested that in spite of neuronal degeneration during aging, these responses to stress can be maintained by compensatory efforts of neurons that remain intact.

Impairments in lactation after electrolytic lesions of the median raphe (MR) nucleus have been corrected by treatment with PRL. Specific serotonin neurotoxin lesions were used in the present study to determine whether decrements in litter growth after electrolytic lesions could be attributed to serotonergic neuron damage at the MR locus, and whether MR lesions (MRL) disrupted suckling-induced PRL release. Intracerebral microinjection of 5,7-dihydroxytryptamine (5,7-DHT) into the MR nucleus produced dose-related decrements in litter growth after either 4 micrograms (sham, 1.35 +/- 0.05; MRL, 1.04 +/- 0.05 g/pup X day; P less than 0.001) or 8 micrograms 5,7-DHT (sham, 1.35 +/- 0.06; MRL, 0.87 +/- 0.11 g/pup X day; P less than 0.001). Despite hypothalamic serotonin depletions of 15% and 55%, respectively, for the two doses of 5,7-DHT, there was no difference between sham and MRL animals in either basal or suckling-induced PRL release. When lesions were placed on day 1 of lactation (L) so that killing on day 7-L corresponded to the early maximal neurotoxin effect, MRL mothers still showed litter growth decrements (0.37 +/- 0.07; sham, 0.98 +/- 0.08 g/pup X day; P less than 0.001) and normal PRL values. When maternal behavior was examined, MRL animals exhibited a higher incidence of abnormal behaviors (failure to retrieve pups, cannibalism, and failure to initiate suckling during a 1-h test period; Fisher's exact P, Sham vs. MRL, less than 0.01, less than 0.05, and 0.15, respectively) than sham animals or animals with 5,7-DHT lesions in the dorsal raphe nucleus or superior colliculus. In addition, suckling behavior scores, determined from daily suckling behavior observations, were lowest in the MRL group and correlated with litter growth only in this group (r = 0.789; P less than 0.01). These data suggest that serotonergic elements in the MR nucleus play an obligatory role in maintaining normal maternal behavior during lactation, but they are not involved in suckling induced PRL release.

Bombesin (BN), substance P-(SP) and somatostatin (SRIF) were measured in individual laminae of the cervical, thoracic and lumbar (L) spinal cord of control cats, and in the L6 segment of cats receiving a spinal hemisection (L2) or deafferentation via dorsal rhizotomy at L6, 7, S1. The interlaminar distribution of BN, SP, and SRIF was remarkably similar. Highest concentrations were found in the superficial dorsal horn, and progressively less was found proceeding ventrally. Some intersegmental variations in peptide concentration within a single lamina were found. Dorsal rhizotomy caused a significant decline in BN, SP and SRIF in lamina I-III, therefore all three peptides appear to be contained in dorsal root ganglion cells. Evidence is presented for the existence of ascending BN and SP projections originating in lamina I-III and VII, for a descending SRIF pathway terminating in lamina VIII, and for an ascending BN path in lamina VIII. Dorsal root afferents to lamina VIII influence levels of BN, SP and SRIF.

Adult male Swiss-Webster (NIH) mice were isolated for 6 weeks. Aggressive behavior was tested on 2 occasions, 24 hours apart. Immediately following the 2nd test period, aggressors and isolated non-aggressors (controls) were decapitated and alpha-MSH concentration was measured in discrete areas of the brain. Only the nucleus accumbens and preoptic lateralis of the aggressors, showed a higher level of alpha-MSH when compared to the controls. The significance of these changes is discussed.

Norepinephrine (NE) concentrations were measured by radioenzymatic assay in microdissected individual laminae of each segment of the cat spinal cord. Norepinephrine was detected in all areas of the spinal gray matter and showed more than a 7-fold difference in concentration between the laminae with the highest and lowest NE. The cervical, thoracic, and lumbosacral spinal regions showed significant interlaminar differences in NE. Intersegmental changes in NE were seen within single laminae of the thoracic and lumbosacral spinal cord, but not in the cervical spinal cord. A significant rostral to caudal, increasing regional gradient of NE was observed from the cervical to lumbosacral spinal cord in laminae I-III, V, VI, VII, and IX. In the intermediolateral cell column (IML), epinephrine concentrations were 2 to 5% of NE. Neither neurotransmitter showed a significant intersegmental variation in the IML. These data should prove useful in further defining the precise role of NE in specific regions of the spinal cord that mediate sensory, motor, autonomic, or propriospinal functions.

The distribution of alpha-melantropin-like material (alpha-MSH) was demonstrated in rat brain using a microdissection technique combined with radioimmunoassay. Highest concentrations of alpha-MSH were noted in the hypothalamus and preoptic area. Particularly high concentrations were observed in the arcuate nucleus, median eminence, suprachiasmatic nucleus, periventricular nucleus and the medial preoptic nucleus. The thalamic paraventricular nucleus also contained high alpha-MSH concentrations. Moderate to low concentrations were noted in other thalamic, septal, amygdaloid and midbrain nuclei. Low concentrations were observed in cortical and striatal regions.

Binding characteristics of 3H-Substance P (SP) were studied with rat brain membranes using a method applied to peripheral tissues by Lee and Snyder [15]. This method was well applicable to central nervous system (CNS) tissues. The results in the present study indicate that specific 3H-SP binding reaches a plateau only after 20 minutes of incubation, and the binding sites are saturable at a relatively low concentration of 3H-SP. Scatchard analysis of specific binding data reveals a single class of binding sites with a high affinity (Kd = 0.30 nM) and a low density (Bmax = 27.7 fmol/mg protein) in rat brain membranes. A Hill plot of the displacement curve of 3H-SP with unlabelled SP showed no indication for cooperativity (nH = 0.83). The relative potencies of binding of various SP fragments at 3H-SP binding sites were fairly parallel to the length of the C-terminal fragments. Neurotransmitters not structurally related to SP produced no effect on 3H-SP binding even when used at micromolar concentrations.

Male mice of 3 different strains (NIH, C57BR/cdJ and A/HeJ) were exposed individuality (victims) to attack by trained fighter Swiss Webster mice for 10 minutes daily for various numbers of days. Immediately after the last attack the victim mice were decapitated along with unattacked control mice of the appropriate strain, and plasma norepinephrine (NE) and epinephrine (E) were measured. The concentration of NE was significantly lower in decapitated C57BR/cdJ mice than in the other 2 strains. The concentrations of E and NE in the plasma of decapitated C57BR/cdJ and A/HeJ mice were significantly greater after 4 days of attacks, whereas in NIH mice plasma levels of only NE were greater and this occurred only after 14 days of attacks. After 7 days of exposure to attack, C57BR/cdJ and A/HeJ victim mice were permitted to rest for various periods of time. In C57BR/cdJ animals plasma E returned to almost normal levels after 2 days, and NE after 4 days, while in A/HeJ mice plasma E and NE returned to control levels already after 1 day of rest.

Several earlier studies reported that the acute administration of L-tryptophan to adult rats caused an increase in brain serotonin levels. This study describes the effects of chronic tryptophan loading on serotonin concentration levels in various regions of the neonatal rat brain. Rats were injected with tryptophan methyl ester hydrochloride (100 mg/kg), intraperitoneally, daily from day 4 to day 24 after birth, and sacrificed on days 8, 19, and 29 after first injection. The brains were immediately dissected into their component regions, and serotonin concentration levels were measured by a radioenzymatic method. Chronic tryptophan loading produced a significant (P < .05) decrease in serotonin levels in all the brain regions as compared with saline-treated controls, except the pons and medulla regions, which showed significant (P < .001) increase on day 8.

Norepinephrine (NE) and dopamine (DA) levels and turnover were measured in 17 discrete brain regions of Swiss-Webster (NIH) mice made aggressive by prolonged isolation. The NE steady state level was significantly lower in olfactory tubercle and substantia nigra and significantly higher in the septal area of the aggressive mice when compared to the isolated non-fighter controls. NE turnover was only higher in the A-10 region of the aggressors. DA steady state level and turnover was lower in olfactory tubercle and higher in caudate putamen of the aggressors. The significance of these changes in isolation-induced aggression is discussed.

Short and long term effects of p-chloroamphetamine (PCA) on levels of catecholamines (CA) in discrete CA cell body and axon terminal areas were investigated. The levels were unaffected, except for a transient fall in dopamine in the arcuate nucleus. These results do not support the suggestion that PCA is neurotoxic to CA cells.

The effects of prolonged (2 months) corticosterone (CORT) treatment on several cholinergic markers of various brain areas were compared to the effects of prolonged intermittent exposure to stress. CORT, but not stress, caused a significant reduction in the number of acetylcholinesterase-stained neurons in the medial septal area. Neither treatment resulted in any hippocampal pyramidal cell loss. It is concluded that a time-dependent degeneration of the septohippocampal cholinergic system follows 2 months of CORT administration but not chronic intermittent stress of this duration.

Inbred Wistar-Kyoto rats which are behaviorally more reactive to stress have a shorter life span than Brown-Norway rats. This is paralleled by higher basal activity and more pronounced changes in the septohippocampal cholinergic system of Wistar-Kyotos after stress. Age- and strain-dependent differences were therefore characterized in the septohippocampal system of 3- and 24-month-old (aged) Wistar-Kyotos and Brown-Norways, and in 30-month-old Brown-Norways. High affinity [3H]choline uptake and newly synthesized [3H]acetylcholine release served as markers for cholinergic terminals in the hippocampus. [3H]Quinuclidinylbenzilate binding served as a marker of muscarinic receptors in the hippocampus. Choline acetyltransferase activity served as a marker for cholinergic neurons and their terminals in the septum and hippocampus respectively. Acetylcholinesterase histochemical staining served to localize cholinergic neurons and their terminals in the septum and hippocampus respectively. In the hippocampus of aged Wistar-Kyotos choline uptake and acetylcholine release were reduced by approximately 50% compared to their young counterparts, but remained unchanged in aged Brown-Norways. Hippocampal choline acetyltransferase activity, acetylcholinesterase staining and muscarinic binding were unchanged in aged rats of both strains. Pyramidal cell loss (observed in Cresyl violet stained sections) was detected in hippocampus of 24-month-old Wistar-Kyotos and 30-month-old, but not younger Brown-Norways. Numbers of acetylcholinesterase-stained cells in the septum were reduced by 45 and 25% in 24-month-old Wistar-Kyotos and Brown-Norways respectively, and by 50% in 30-month-old Brown-Norways. Mean diameter of these cells was increased only in aged Wistar-Kyotos (approximately 46%) and in 30-month-old Brown-Norways (40%). The results indicate: (1) there is an ongoing age-dependent degeneration of septohippocampal cholinergic neurons which is associated with two principal compensatory changes in remaining cholinergic neurons: (a) hypertrophy of perikarya and (b) relative increase in activity of presynaptic markers in terminals with unchanged regional distribution, suggesting possible collateral sprouting; (2) age-dependent loss of septal cholinergic neurons precedes loss of hippocampal pyramidal neurons and (3) loss of pyramidal neurons in the hippocampus is associated with a compensatory increased muscarinic binding by remaining target hippocampal neurons. The results imply that higher basal and stress-induced activity of septohippocampal cholinergic neurons may be correlated with an accelerated and more pronounced age-dependent degeneration of this cholinergic system.(ABSTRACT TRUNCATED AT 400 WORDS)