Changes in alpha-melanotropin in discrete brain areas of isolated aggressive mice

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.

N-acetylation regulates the behavioral activity of alpha-melanotropin in a multineurotransmitter neuron

A multineurotransmitter neuronal system that synthesizes and secretes both acetylated and deacetylated forms of alpha-melantropin and beta-endorphin is present in rat and human brain. The N-acetylated from of alpha-melanotropin had more potent behavioral effects than the deacetylated alpha-melanotropin. In the case of beta-endorphin, however, the deacetylated form has been shown to be more potent than the acetylated form. Enzymatic N-acetylation appears to be an important regulatory process for modulating the behavioral activity of peptides secreted from the opiomelanotropinergic multineurotransmitter neuron.

Selective chemical hepatic sympathectomy in the dog

Intraportal injection of 6-hydroxydopamine (6-OHDA) was used to produce selective hepatic sympathectomy in the dog. Previously reported techniques for 6-OHDA induced hepatic sympathectomy in rats and cats were modified considerably using alpha and beta adrenergic blocking agents to prevent the otherwise intense and fatal sympathomimetic response which has prevented adaptation of the intraportal 6-OHDA injection for dogs. After 6-OHDA injection, histofluorescent staining demonstrated loss of hepatic adrenergic nerves with preservation of normal adrenergic innervation in the heart and pancreas. Tyramine iv was used to further document functional integrity of peripheral sympathetic mechanisms. This technique provides a useful model for evaluation of sympathetic nervous system mediated changes in hepatic metabolic function associated with the neuroendocrine response to hemorrhage in the classic dog model.

Hypothalamic sites for cardiovascular and sympathetic modulation by prostaglandin E2

Prostaglandin E2 (PGE2, 0.5 - 5 nmol/kg) injected into the lateral cerebral ventricle of the rat increased the systemic blood pressure and heart rate in a dose dependent manner. These effects were accompanied by increases in plasma norepinephrine and epinephrine concentration. Injection of low dose of prostaglandin E2 into discrete hypothalamic nuclei induced a marked increase in heart rate, a moderate increase in the arterial blood pressure and a significant elevation of plasma norepinephrine level. This study suggests a possible central role for PGE2 in modulation of cardiovascular dynamics and sympathetic nervous activity.

Catecholamines and vasopressin in forebrain nuclei of hypertension prone and resistant rats

Catecholamine and vasopressin content were studied in discrete brain nuclei of the Sabra strain of hypertension prone (SBH) and resistant (SBN) rats. Higher concentrations of dopamine, norepinephrine and epinephrine were observed in the median eminence of SBN compared to SBH or controls (SB) rats. Dopamine and epinephrine levels were higher in the lateral septal nucleus of SBH rats as compared to SBN or SB. Vasopressin content in discrete regions along the hypothalamo-pituitary axis was elevated in both SBH and SBN as compared to SB, but were especially elevated in the SBH group. The catecholamine and vasopressin changes found in SBH are different than those described in other genetically hypertensive rats indicating a difference in either the pathogenesis or central response to hypertension of this strain.

Effect of capsaicin administration to neonatal rats on the substance P content of discrete CNS regions

Substance P (SP) levels were determined by radioimmunoassay in microdissected CNS regions of adult animals treated with capsaicin as neonates and of vehicle controls. Capsaicin treatment reduced the SP content of the spinal trigeminal nucleus and the dorsal horn of the spinal cord whereas it had no effect on the SP levels in the ventral horn of the spinal cord, the nucleus tractus solitarius or in midbrain and forebrain areas analyzed.

Lithium increases serotonin release and decreases serotonin receptors in the hippocampus

The effects of long-term lithium administration on pre- and postsynaptic processes involved in serotonergic neurotransmission were measured in rat hippocampus and cerebral cortex. Long-term lithium administration increased both basal and potassium chloride-stimulated release of endogenous serotonin from the hippocampus but not from the cortex. Serotonergic receptor binding was reduced in the hippocampus but not in the cortex. These results suggest a mechanism by which lithium may stabilize serotonin neurotransmission.

Gastric and pyloric motor response to sympathetic nerve stimulation after chemical sympathectomy

This study evaluated the effect of electrical stimulation of the greater splanchnic nerve on gastric and gastroduodenal motility in 6-hydroxydopamine (6-OHDA)-pretreated anesthetized dogs. Biopsies from the stomach, pylorus and duodenum were obtained and analyzed by catecholamine fluorescence microscopy. Degeneration of adrenergic terminals in Auerbach's plexus was complete at 1 week. The majority of stimulations in control dogs or dogs treated with 6--OHDA produced contractions in the gastric body, antrum, and pylorus and relaxation of inhibition in the duodenum. The excitatory motor responses in the gastric body, antrum and pylorus were unaffected by the administration of hexamethonium. Following atropine administration, contractions due to splanchnic nerve stimulation virtually were abolished in the antrum, pylorus and duodenum and were reduced in number in the gastric body. Relaxation and inhibition were no longer observed in the duodenum after atropine. The greater splanchnic nerve appears to contain both excitatory are inhibitory cholinergic pathways to the musculature of the stomach, pylorus, and duodenum.

Identification, characterization, and distribution of secretin immunoreactivity in rat and pig brain

Secretin immunoreactivity was detected in the central nervous system of the rat and pig with a highly specific radioimmunoassay. The secretin immunoreactivity in the rat and pig brain and duodenum extracts was fractionated by using a reverse-phase high-pressure liquid chromatographic system. The immunoreactive secretin from pig brain and duodenum coeluted precisely with synthetic porcine secretin. However, immunoreactive secretin extracted from rat brain and duodenum eluted slightly before porcine secretin. These data suggest a slight difference in the structure of rat and pig secretin. The detection of secretin in the brain lays the groundwork for studies to determine the role of the peptide in central nervous system function.

Cardiovascular and sympathetic responses to PGF2 alpha injection into hypothalamic nuclei

Injection of prostaglandin F2 alpha (1 nmol/rat) into the paraventricular, dorsomedial and posterior hypothalamic nuclei of halothane anesthetized rats elicited rapid increases of heart rate and blood pressure. The injection of this same dose of prostaglandin F2 alpha into the cerebroventricular system or intravenously had no effect on these parameters. The cardiovascular responses observed following prostaglandin F2 alpha injection into these hypothalamic nuclei were accompanied by increases in plasma levels of norepinephrine and epinephrine, with peak levels at the maximal cardiovascular response. This study suggests a possible role for prostaglandin F2 alpha in modulation of the cardiovascular system via specific hypothalamic nuclei.

Secretin immunoreactivity in rat and pig brain

Secretin immunoreactivity in rat and pig brain has been identified and characterized utilizing a highly specific radioimmunoassay and fractionation on a high pressure liquid chromatographic system reverse phase column. One immunoreactive peak from each brain extract was observed. Secretin immunoreactivity from rat brain and duodenum coelute, but eluted slightly ahead of the immunoreactivity from pig brain and duodenum and from synthetic porcine secretin. Immunoreactive secretin is widely distributed in the thalamus, hypothalamus and olfactory bulb, cerebral cortex, midbrain, septum, striatum, hippocampus, medulla and pons. The highest concentrations occur in the pineal and the pituitary gland.

Biochemical localization and characterization of bombesin-like peptides in discrete regions of rat brain

A radioimmunoassay using an antiserum which recognizes the C-terminal of bombesin was used to determine the regional distribution of bombesin-like peptides in discrete regions of rat brain. The concentration of endogenous bombesin-like peptides was 30-fold greater in high (substantia gelatinosa trigemini, nucleus tractus solitarius, interpeduncular nucleus and arcuate nucleus) than low regions (caudate, hippocampus and cingulate cortex). When brain extracts were fractionated using high pressure liquid chromatography techniques two major peaks of immunoreactivity were obtained, the more hydrophobic peptide coeluted with synthetic bombesin. It is concluded that the current evidence supports the contention that bombesin may be a neuroactive peptide in the brain.

Comparison of biological and behavioral activities of alpha- and gamma-melanocyte stimulating hormones

The biological and behavioral activities of gamma-MSH (gamma-MSH) and alpha-MSH (alpha-MSH) were compared using three different tests: darkening of the skin of Anolis, grooming behavior of rats, and performance of a visual discrimination task by rats. When incubated with the Anolis skin, both peptides cause skin darkening. However, alpha-MSH is much more potent than gamma-MSH. The alpha-MSH effect is not antagonized by coincubation with gamma-MSH. When given intraventricularly to rats, alpha-MSH induces a marked grooming behavior. This effect was not noted upon administration of gamma-MSH. Injection of gamma-MSH with the alpha-MSH did not produce a grooming response significantly different from alpha-MSH alone. In the visual discrimination task, the two peptides had opposite effects on the rate at which rats learned the initial discrimination and a subsequent reversal. The peptides were injected intraperitoneally prior to behavioral testing. Following alpha-MSH, rats learned the discrimination and subsequent reversal faster than the control rats. Following gamma-MSH, rats learned the initial discrimination at approximately the same rate as controls, and learned the reversal much slower. These results are discussed in terms of the similarity and differences in the mechanisms of action of alpha-MSH and gamma-MSH.

Release of alpha-melanocyte stimulating hormone into rat and human cerebrospinal fluid in vivo and from rat hypothalamus slices in vitro

The release of alpha-melanocyte stimulating hormone (alpha-MSH) from central nervous system neurons was investigated and demonstrated in vivo and in vitro. alpha-MSH immunoreactivity in rat and human cerebrospinal fluid (CSF) is comprised of deacetylated alpha-MSH, alpha-MSH and the methionine sulfoxide forms of these peptides. The sulfoxides are formed artifactually upon extraction. alpha-MSH in rat CSF is unaffected by hypophysectomy but is markedly increased by electrical stimulation of the mesencephalic central gray. These data indicate that CSF alpha-MSH is primarily of neuronal origin, alpha-MSH is also released in a calcium dependent manner from hypothalamic slices in vitro. The fact that the release of alpha-MSH is stimulated by veratridine and inhibited by tetrodotoxin demonstrates the necessity for neuronal sodium influx for alpha-MSH release. The presence of an alpha-MSH neurosecretory process supports a neurotropic role for this peptide in the central nervous system.

The distribution of bovine pancreatic polypeptide-like immunoreactive neurons in rat brain

Using the indirect immunofluorescent technique, bovine pancreatic polypeptide (BPP)-like immunoreactive nerve fibers and cell bodies were observed widely distributed in rat brain. A detailed stereotaxic atlas of BPP-immunoreactive neurons was prepared. Large numbers of BPP-containing perikarya were observed in the acute nucleus, with scattered cells in the cerebral cortex, nucleus olfactorius anterior, nucleus tractus diagonalis, olfactory tubercle, nucleus accumbens, neostriatum, nucleus interstitialis stria terminalis, nucleus preopticus medialis, area retrochiasmatica, zona interna of the median eminence, substantia grisea centralis, locus coeruleus, nucleus tractus solitarius, and in the region of the nucleus reticularis lateralis. Large numbers of varicose BPP-like nerve fibers were observed in the following nuclei: accumbens, interstitialis stria terminalis, preopticus medialis, preopticus suprachiasmaticus, suprachiasmaticus, periventricular thalamic and hypothalamic, paraventricularis, dorsomedialis, ventromedialis, arcuatus, parabrachialis dorsalis, tractus solitarius and the substantia gelatinosa trigemini. The present findings suggest that a BPP-like peptide may be involved in significant neuronal circuitry, possibly in a neurotransmitter or neuromodulator role. However, the exact identity of this peptide and its physiological role remain to be determined.

Mapping of motilin-immunoreactive neurons of the rat brain

Motilin immunofluorescence was observed in the rat brain by means of N- and C-terminally directed antisera. A detailed mapping of the localization of motilin-like immunoreactive neurons in the rat forebrain is presented. Colchicine pretreatment revealed many cell bodies in the mediobasal hypothalamus. A small number of cells were observed in the organum vasculosum lamina terminalis (OVLT) region. A rich innervation of varicose fibers was observed in the median eminence and OVLT. Fibers of varying densities were observed in the preoptic area, nucleus interstitialis stria terminalis, hypothalamic nuclei, basal hypothalamus, amygdala, mammillary doby and central gray. The localization of these neurons suggests that motilin, like other brain peptides serves a variety of functions including neuroendocrine regulation.

Evidence that N-acetylation regulates the behavioral activity of alpha-MSH in the rat and human central nervous system

alpha-MSH immunoreactive peptides were fractionated and characterized in rat and human brain and rat pituitary by reversed phase high pressure liquid chromatographic techniques. alpha-MSH and deacetylated alpha-MSH were two major naturally existing peptides in both brain and pituitary gland. Subsequent experiments examined the roles of these two peptides in neuronal function. The alpha-MSH was clearly more effective than deacetylated alpha-MSH in improving performance on a visual discrimination task after intraperitoneal administration and in inducing excessive grooming after intraventricular administration. The difference in behavioral potency may be explained by the fact that alpha-MSH was much more resistant to peptidase degradation than was deacetylated alpha-MSH. N-acetylation of alpha-MSH may be an effective regulatory process for modulating the behavioral potency of the secretory product of alpha-MSH-containing pituitary cells and neurons.

Identification, characterization and distribution of motilin immunoreactivity in the rat central nervous system

Motilin-immunoreactivity was evaluated in rat brain using 15 different antisera and by combining gel filtration, high pressure gel filtration and reverse phase high pressure liquid chromatography with radioimmunoassay. Gel filtration chromatography demonstrated a high molecular weight and low molecular weight form of immunoreactive motilin. The high molecular weight form predominated in brain while the low molecular weight peptide was the predominant form of duodenum. The low molecular weight immunoreactive motilin was indistinguishable from synthetic porcine motilin by gel filtration and high molecular weight gel filtration. Low molecular weight rat motilin could, however, be distinguished from synthetic porcine motilin by high pressure liquid chromatography and certain antisera. Immunological results suggest that the slight structural difference may be in the N-terminal portion of the molecule. Immunoreactivity was measured in grossly and microdissected regions of the rat brain. The peptide had quite a unique distribution as highest concentrations are observed in the cerebellum. High concentrations were also observed in hypothalamic nuclei. Particularly high concentrations were noted in the organum vasculosum lamina terminalis. Lowest motilin concentrations in the rat brain were in the pons and the medulla. The distribution of motilin in rat brain suggests that it may have roles in regulating both neuroendocrine and neurological processes.

Evidence that noradrenaline modulates the increase in striatal dopamine metabolism induced by muscarinic receptor stimulation

The effect of oxotremorine was studied on the concentration of homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenylethylglycol (MHPG) in the corpus striatum of rats. At a dose of 1 mg/kg oxotremorine increased HVA levels by 68% and MHPG, by 51%. MHPG was also increased in the nucl. accumbens (58%) and neocortex (42%). Pretreatment with clonidine, 0.1 mg/kg abolished the increase in MHPG in the striatum and significantly inhibited the rise in HVA. 1-Propranolol 2.5 mg/kg, but not d-propranolol, had an effect similar to that of clonidine. A lower dose of oxotremorine (0.5 mg/kg) increased striatal HVA by 36% but did not alter MHPG levels. This increase in HVA was not reduced by 1-propranolol. Eight days after bilateral lesions of the locus coeruleus, there was a reduction in the basal concentrations of noradrenaline (41%) and MHPG (57%) in the striatum. The data suggest that at higher doses of oxotremorine (1 mg/kg), but not a lower dose (0.5 mg/kg), a noradrenergic pathway is stimulated to increase the rate of metabolism of noradrenaline in the striatum. Oxotremorine also appears to increase dopamine metabolism in the striatum by at least two separate mechanisms, one of which involves the mediation of noradrenaline.

Discrete regional analysis of norepinephrine, dopamine, choline acetyltransferase and glutamic acid decarboxylase in the brain of the newborn and pubescent monkey

A method is described for the removal of discrete areas of the monkey brain. A detailed mapping of norepinephrine, dopamine, choline acetyltransferase and glutamic acid decarboxylase in the newborn and pubescent monkey brain is presented.

Changes in central cholinergic neurons in the spontaneously hypertensive rat

The activity of choline acetyltransferase (ChAT) was measured in discrete areas of the brain in 4-, 8- and 12-week-old spontaneously hypertensive rats (SH rats) and age matched Wistar Kyoto (WKY rats) controls. The concentration of acetylcholine (ACh) was also measured in certain hindbrain nuclei of 12 week SH and WKY rats. An increase in the ChAT activity and ACh concentration in the locus coeruleus was detected in 12-week-old SH rats. Decreases in the ChAT activity were found in several hypothalamic nuclei of SH rats, specifically in the paraventricular nucleus of 4-week-old rats, in the dorsomedial nucleus at 8 and 12 weeks and in the posterior hypothalamic nucleus at 12 weeks. Changes in ChAT activity were also detected in 4- and 8-week-old SH rats in the anterior ventral thalamus and in the nucleus gigantocellularis. These results suggest that cholinergic nerve activity in certain rat brain areas, several of which play a role in cardiovascular control, is altered in spontaneously hypertensive rats.

Effects of food restriction on the periodicity of corticosteroids in plasma and on monoamine concentrations in discrete brain nuclei

The concentrations of plasma corticosteroids and of norepinephrine, dopamine and serotonin in microdissected brain regions were measured at 08.00, 12.00 and 20.00 h in male rats fed ad libitum and in rats whose food intake was restricted to 09.30-11.30 h. In ad libitum fed animals, plasma corticosteroids were lowest at 08.00 and highest at 20.00 h. As demonstrated previously, restriction of food availability was associated with appearance of a peak in corticosteroids at 08.00 h. In ad libitum fed animals, serotonin and dopamine concentrations in the median eminence were higher at 20.00 than at 08.00 h. Restriction of food availability significantly decreased the levels of these neurotransmitters at 20.00 h. In the paraventricular nucleus, amygdala, and hippocampus of ad libitum fed animals, serotonin levels were lower at 20.00 than at 08.00 or 12.00 h. In food-shifted animals, this pattern was reversed so that lowest levels of serotonin occured at 08.00 and markedly elevated levels were observed at 12.00 and 20.00 h. No changes were noted in norepinephrine content of the median eminence or paraventricular nucleus of ad libitum fed or food restricted animals. These results indicate that the shift in the periodicity of corticosteroid secretion produced by a restricted feeding regime is accompanied by changes in the periodicity of neurotransmitter concentrations in specific regions of the brain, and that such patterns are dissimilar in different regions.

Demonstration of an endogenous circadian rhythm of alpha-melanocyte stimulating hormone in the rat pineal gland

alpha-Melanocyte stimulating hormone (alpha-MSH) has been identified and characterized in the rat pineal gland by a combination of immunochemical and high pressure liquid chromatographic techniques. The immunoreactivity in pineal extracts was separated into two chromatographic components. The major component had a retention time identical to that of alpha-MSH while the minor component eluted just slightly before standard alpha-MSH. Male rats maintained in a 12 h photoperiod demonstrated a marked circadian rhythm in pineal alpha-MSH concentration. Concentrations that peaked at 07.00 h, 1 h after the lights were turned on, were greater than 5 times the nadir which occurred at 01.000 h. Animals house in chronic dark for 7 days maintained the diurnal variation of alpha-MSH concentrations. However, in chronically dark housed rats, the peak shifted to 05.000 h and was greater than 10 times the nidir of this rhythm and approximately 4 time the peak at 07.00 in alternating light/dark conditions. Rats exposed to chronic light for 7 days maintained a pineal alpha-MSH rhythm although the amplitude of the peak was significantly decreased compared to the rhythm in animals housed in alternating light/dark conditions. Neither hypophysectomy nor superior cervical ganglionectomy had any effect on the alpha-MSH rhythm. Lesion of the arcuate nucleus, the major source of alpha-MSH-containing nerves in the brain, did not significantly affect pineal alpha-MSH concentrations. These data demonstrate a circadian alpha-MSH rhythm in the rat pineal and suggest an alpha-MSH involvement in the rhythmic processes of the pineal gland.

Localization of substance P immunoreactive nerves in the carotid body

Immunofluorescent histochemical observation of the rat carotid body revealed the presence of substance P immunoreactive fibers. This supports the hypothesis that substance P is a neurotransmitter of chemoreceptor afferent nerves.

Bovine parathyroid catecholamines: a chemical and histochemical study

Bovine parathyroid glands contain large amounts of dopamine (3.4-13.9 pg/microgram), but very little norepinephrine. Fluorescent histochemistry demonstrates only rare adrenergic nerve terminals on vasculature. Single dopamine-containing cells, most likely mast cells, are scattered in large numbers throughout the connective tissue stroma.

Demonstration of substance P in aortic nerve afferent fibers by combined use of fluorescent retrograde neuronal labeling and immunocytochemistry

Combined use of the intraaxonal retrograde transport of the fluorescent marker 'true blue' with substance P (SP) immunocytochemistry has been used to trace the nodose ganglion projections of SP-containing neurons of the aortic depressor nerve. It has been found that (1) SP immunoreactive (SP-I) cell bodies are clearly demonstrable in clusters in the rostral part of the nodose ganglion without the aid of colchicine pretreatment; (2) 'true blue' is retrogradely transported to the nodose ganglion following its application to the central cut end of the aortic nerve; (3) 'true blue' fluorescence and SP fluorescent immunoreactivity can be visualized in the same tissue section and certain cell bodies in the nodose ganglia contain both SP-I and retrogradely transported 'true blue'. These results indicate that the aortic nerve which projects from the aortic arch baro- and/or chemoreceptors to brainstem vasomotor centers contains SP-I afferent fibers which emanate form the nodose ganglion.

Isolation induced aggression and catecholamine variations in discrete brain areas of the mouse

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.

Substance P as a baro- and chemoreceptor afferent neurotransmitter: immunocytochemical and neurochemical evidence in the rat

The possibility that substances P (SP) is a neurotransmitter of baro- and chemoreceptor afferents in the rat was investigated. SP-like immunoreactivity (SP-I) was analyzed quantitatively by radioimmunoassay in various levels of the nucleus tractus solitarius (NTS), the site of termination of these afferents while SP-containing afferent neurons were studied in various portions of the peripheral pathways by immunocytochemistry. It was found that the NTS contained significant amounts of SP-I and that unilateral removal of the nodose ganglia reduces the SP-I content of those portions of the NTS known to receive vagal afferents. In addition, SP-I was visualized in discrete fibers in the tunica adventitia of the aortic arch and carotid sinus regions, the vagus nerve and nodose ganglia. These results in the rat are consistent with our previous studies in the cat and provide further evidence that SP is contained within baro- and chemoreceptor afferent nerves.

Identification and distribution of alpha-melanotropin in discrete regions of the cat brain

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.

Effects of suckling on serum prolactin levels and catecholamine concentrations and turnover in discrete brain regions

The effects of suckling on serum prolactin levels and catecholamine concentrations and turnover were examined in several discrete brain regions. Turnover rates were assessed by using the synthesis inhibitor alpha-methyltyrosine (alpha-MT) in combination with microdissection techniques for the removal of individual brain regions and sensitive radioenzymatic assays for norepinephrine (NE) and dopaime (DA). Prolactin secretion was induced by mothers experiencing 6 h of pup removal with subsequent pup replacement. Suckling or the administration of alpha-MT to mothers resulted in a marked increase in circulating titers of prolactin. A decrease in steady-state NE concentrations in the anterior hypothalamus and a decrease in steady-state DA concentrations in the ventromedial nucleus were noted in suckled mothers. The comparison of relative rates of NE depletion after alpha-MT treatment revealed a suckling-induced increase in turnover in the ventromedial nucleus and a suckling-induced decrease in turnover in the anterior hypothalamus. Neither suckling nor alpha-MT treatment produced any changes in NE or DA turnover rates in the arcuate nucleus or median eminence. These findings demonstrate that suckling-induced activation of prolactin results in changes in noradrenergic processes in the ventromedial and anterior hypothalamic nuclei. This suggests an involvement of noradrenergic systems in suckling-induced prolactin release.

Identification, characterization and stereotaxic mapping of intraneuronal alpha-melanocyte stimulating hormone-like immunoreactive peptides in discrete regions of the rat brain

A highly specific antibody to alpha-melanocyte stimulating hormone (alpha-MSH) was used to histochemically localize and biochemically identify and quantitate alpha-MSH immunoreactivity in nerve fibers and cell bodies of the rat brain. alpha-MSH-like immunoreactivity was contained in fibers throughout the brain. The distribution of alpha-MSH was determined by immunocytochemistry as well as by radioimmunoassay combined with microdissection techniques. High concentrations of alpha-MSH were contained in the nucleus interstitialis stria terminalis, the median eminence and the medial preoptic, anterior hypothalamic, periventricular, paraventricular, arcuate, dorsomedial, and posterior hypothalamic nuclei. Moderate alpha-MSH concentrations were noted in the amygdala, septum, central gray, dorsal raphe, and the nucleus tractus solitarius. Cell bodies containing alpha-MSH were observed only in the arcuate nucleus. The alpha-MSH-like compound in brain had similar immunochemical and electrophoretic properties of standard alpha-MSH but high pressure liquid chromatographic analysis demonstrated that the alpha-MSH-like immunoreactivity was comprised of one major and two minor components. The major immunoreactive peak had an identical retention time as alpha-MSH and therefore may be chemically identical to alpha-MSH. The similar retention times and immunoreactivity of the other two compounds suggest a similarity in size and structure to alpha-MSH. These observations demonstrate that fibers containing alpha-MSH emanate from the arcuate nucleus to innervate many other regions of the rat brain.

Effect of hypophysectomy on alpha-melanotropin in discrete regions of the rat brain

The effect of hypophysectomy on alpha-melanotropin (alpha MSH) concentrations in discrete brain regions was investigated. Hypophysectomy resulted in a 38-69% decrease in alpha MSH concentration in alpha MSH terminal regions 4 weeks after surgery. In contrast, the alpha MSH concentration in the arcuate nucleus, site of alpha MSH containing perikary, was unaffected by hypophysectomy. These results indicate that the brain alpha MSH system is distinct from, but related to that of the pituitary.

Biochemical mapping of the noradrenergic ventral bundle projection sites: evidence for a noradrenergic--dopaminergic interaction

Norepinephrine (NE) and dopamine (DA) concentration and dopamine turnover were measured 12 days after a unilateral or bilateral noradrenergic ventral bundle (VB) transection to determine the noradrenergic projection sites and possible interactions with dopaminergic systems. Both bilateral and unilateral VB transection resulted in a significant reduction of NE of the nucleus accumbens, lateral septal nucleus, medial forebrain bundle, ventromedial nucleus, dorsomedial nucleus and medial amygdaloid nucleus. Bilateral transection also decreased NE content of the median eminence and the periventricular and arcuate nuclei. In the medial preoptic nucleus, the nucleus interstitialis striae terminalis and the central gray catecholamine area, bilateral transection significantly decreased NE concentrations while unilateral lesions had no significant effect. The anterior hypothalamic, lateral preoptic, and paraventricular nuclei responded to bilateral VB transection with a decrease in NE concentration and to unilateral lesion with a bilateral increase in NE. In the dorsal hippocampus and the caudate nucleus, bilateral lesions had no effect on NE concentrations while unilateral transection significantly decreased NE concentrations. Regions in which neither bilateral nor unilateral VB transection produced a significant change in NE content are the olfactory tubercle, the nucleus tractus diagonalis, substantia nigra pars compacta and reticulata, ventral tegmental area, habenula, superior colliculus, and the cingulate and piriform cortices. Transection of the noradrenergic ventral bundle also produced changes in dopaminergic systems suggesting a noradrenergic--dopaminergic interaction. Bilateral VB transection decreased the dopamine concentration and turnover in the nucleus accumbens, increased steady-state levels and turnover in the nucleus tractus diagonalis and increased dopamine concentration in the lateral septum. Unilateral VB transection decreased DA concentration bilaterally in the caudate nucleus, olfactory tubercle, nucleus accumbens and the nucleus interstitialis striae terminalis but increased concentrations in the substantia nigra pars reticulata (ipsilateral) and in the ventral tegmental area (bilateral). These results indicate a broad projection field for the noradrenergic ventral bundle and suggest a noradrenergic--dopaminergic interaction.

Neurochemical and histochemical studies of the effect of a lesion of the nucleus cuneiformis on the cholinergic innervation of discrete areas of the rat brain

The innervation sites of the dorsal tegmental acetylcholinesterase (AChE)-containing pathway were examined in rats by combining histochemical and biochemical techniques. A lesion was placed in the nucleus cuneiformis (midbrain reticular formation) and brains were examined after 4 days survival for changes in AChE staining and choline acetyltransferase (ChAT) activity in discrete brain areas. An ipsilateral projection appears to exist to the anterior thalamic nuclei, lateral portion of the medial thalamic nucleus, parafascicular nucleus, pretectal nucleus, posterior thalamic nucleus, and deep layers of the superior colliculus. A possible bilateral innervation to the reticular nucleus of the thalamus and the dorsal and ventral lateral geniculates was found. The parallel use of AChE histochemistry and measurements of ChAT activity in discrete nuclei will be useful for future evaluation of cholinergic pathways.

Effects of ovarian hormones on levels of luteinizing hormone in plasma and on serotonin concentrations in discrete brain nuclei

Levels of serotonin were measureed in microdissected, individual brain nuclei in ovariectomized rats after treatment with ovarian hormones. Regions sampled included nuclei in the forebrain, rostral and medial hypothalamus, and midbrain tegmentum. Estradiol benzoate decreased levels of luteinizing hormone in plasma but did not affect serotonin levels in any region. Progesterone alone elevated serotonin content in the nucleus tractus diagonalis and ventral tegmental area. The combined estrogen plus progesterone regime produced a surge in plasma luteinizing hormone and also markedly elevated serotonin in the median eminence. These results may be of significance for ovarian hormonal regulation of gonadotropin secretion and reproductive behavior.

Kainic acid-induced neurotoxicity in the striatum: a histofluorescent study

Histochemical observation of catecholamine terminals in the striatum following kainic acid injections revealed a 'sphere of influence' which contained an increased intensity of dopamine fluorescence as well as non-specific tissue destruction at the injection site. The area of involvement was approximately 50% of the striatum and varied somewhat at any one dose range depending upon the site of injection. It is suggested that destruction of regulatory neuronal systems (cholinergic, GABAergic, peptidergic, etc.) results in a net increase of dopamine in the sphere of kainic acid influence.

Specific uptake and retrograde flow of antibody to dopamine-beta-hydroxylase by central nervous system noradrenergic neurons in vivo

This study sought to determine whether the administration in vivo of antibody to dopamine-beta-hydroxylase (AD beta H) is taken up by central noradrenergic neurons and transported by retrograde flow to the cell bodies of origin. AD beta H serum or preimmune serum (control) in volumes of 1--20 microliter were stereotaxically injected into the lateral ventricle. Rats were sacrificed at times ranging from 1 h to 8 days. Cryostat sections were stained with fluorescein conjugated IgG. After 24 h, a bilateral granular fluorescence was seen only in neuronal cell bodies corresponding to noradrenergic cell groups A1--A7 with the most intense fluorescence localized within perikarya and processes of the locus coeruleus (A6) and subcoeruleus. This technique also permitted the visualization of the ascending dorsal and ventral noradrenergic bundles as well as varicose fibers and terminals in a pattern identical to that reported with histofluorescence, autoradiographic, biochemical and classical immunofluorescence techniques for the identification of noradrenergic fiber distributions. At 3 and 6 h, the first detectable fluorescence was observed in forebrain noradrenergic terminals and in fibers of the dorsal and ventral noradrenergic bundles. At 10 h fluorescent varicosities were first visualized within the caudal dorsal bundle and some cytoplasmic fluorescent particles were seen within locus coeruleus cell bodies. After 18 h locus coeruleus and subcoeruleus cell bodies were heavily stained, whereas medullary noradrenergic cell groups and nerve fibers were not labeled until after 24 h. An intense locus coeruleus fluorescence remained for 3 days and was completely absent after 6 days. Bilateral transection of the dorsal noradrenergic bundle in the rostral mesencephalon, at the time of injection, effectively blocked the retrograde transport of fluorescing material to the locus coeruleus. The overall staining pattern suggests that, in vivo, central noradrenergic fibers are capable of taking up antibody to dopamine-beta-hydroxylase. The ability of a dorsal bundle transection to abolish locus coeruleus staining, as well as the time course of AD beta H staining in noradrenergic neurons, suggests that AD beta H is transported via a rapid retrograde flow process. This technique combines retrograde transport of a marker protein with the sensitivity and specificity of immunocytochemical procedures to provide a new tool for the neuroanatomical study of neurotransmitter systems.

Potential noradrenergic regulation of serotonergic neurons in the median raphe nucleus

Pharmacological and morphological evidence suggests that the functional activity of serotonergic neurons may be regulated by catecholamines. We have attempted to reveal a potential pathway by which this interaction might occur. Rats received bilateral knife cut lesions of the ventral noradrenergic bundle which severed the A-1 and A-2 cell body contributions to this projection. Controls received a sham lesion into the cerebellum. Two weeks later all animals were sacrificed, and norepinephrine and serotonin levels were measured in discrete nuclei of the brain. Lesion placement was confirmed histofluorometrically. Serotonin levels in the median raphe nucleus were significantly reduced by 40%, but levels of serotonin were unaffected in the dorsal raphe nucleus and 8 serotonergic terminal regions. The lesions did not affect levels of norepinephrine in the locus coeruleus, cingulate cortex, or habenula. This study suggests that a noradrenergic projection to the median raphe nucleus from the A-1 and A-2 cell body groups may modulate serotonergic neuronal function.

A diurnal rhythm of immunoreactive alpha-melanocyte-stimulating hormone in discrete regions of the rat brain

A significant diurnal variation in alpha-melanocyte stimulating hormone (alpha-MSH) concentrations was observed in discrete regions of the rat brain. During the 12 h light: 12 h dark cycle, alpha-MSH concentrations in each case were highest during the light period and lowest during the dark period. At 09.00 h, 3 h after lights were turned on, the peak alpha-MSH concentration occurred in the median eminence, the arcuate and dorsomedial hypothalamic nuclei and the periventricular thalamic nucleus. The paraventricular and anterior hypothalamic nuclei had highest alpha-MSH concentrations at 13.00 h. In the medial preoptic nucleus, the peak alpha-MSH concentrations appeared at 17.00 h. These changes in alpha-MSH content may reflect an alpha-MSH role in circadian variations in behavioral and neuroendocrine processes.