Neurotensin-containing cell bodies, fibers and nerve terminals in the brain stem of the rat: Immunohistochemical mapping

Neurotensin immunoreactive perikarya, fibers and nerve terminals, visualized by the indirect immunohistofluorescent method in colchicine-pretreated animals, are localized in many discrete regions of the rat brain stem. Cell body groups are found in the inner aspect of the substantia gelatinosa of the caudal trigeminal nuclear complex, the nucleus of the solitary tract, the parabrachial nuclei, the locus coeruleus, the dorsal raphé nucleus, the periaqueductal gray matter, and the ventral tegmental area of Tsai. These areas of cell body density are accompanied by concentrations of fibers and terminals, while the occasional positive perikaryon noted in the dorsal cochlear nucleus is accompanied by only sparse fluorescent fiber/terminal patterns. Other brain stem regions, such as the floor of the fourth ventricle and aspects of the caudal ventrolateral reticular formation, possess substantial numbers of fibers and terminals that are not accompanied by cell bodies. Many aspects of this distribution coincide with the brain stem distribution of the enkephalin pentapeptides, though significant differences in localization are also evident. Interactions of neurotensin with other neurotransmitter candidates are also suggested by its presence in areas enriched in norepinephrine, dopamine, serotonin, and substance P. Certain neurotensin localizations suggest an association of the peptide with functional brain systems preferentially involving these regions. In particular periaqueductal gray and substantia gelatinosa neurotensin synapses are plausible sites for the analgesia elicited after intercisternal injection of low doses of neurotensin.     

Immunohistochemical localization of calretinin in the rat hindbrain

The localization of calretinin in the rat hindbrain was examined immunohistochemically with antiserum against calretinin purified from the guinea pig brain. Calretinin immunoreactivity was found within neuronal elements. The distribution of calretinin-immunoreactive cell bodies and fibers is presented in schematic drawings and summarized in a table. Major calretinin-immunoreactive neurons were found in the lateral and medial geniculate nuclei, substantia nigra, ventral tegmental area, interpeduncular nucleus, periaqueductal gray, mesencephalic trigeminal nucleus, superior and inferior colliculi, pontine nuclei, parabrachial nucleus, dorsal and laterodorsal tegmental nuclei, cochlear nuclei, vestibular nuclei, medullary reticular nuclei, nucleus of the solitary tract, area postrema, substantia gelatinosa of the spinal trigeminal nucleus, and cerebellum. These results show that distinct calretinin-immunoreactive neurons are widely distributed in the rat hindbrain.     

Immunocytochemical localization of the choline acetyltransferase containing neuron system in the rat lower brain stem

This distribution of choline acetyltransferase (CHAT) immunoreactivity (CHAT-I) in the rat lower brain stem was analyzed using a highly sensitive avidin-biotin immunocytochemical method and 3-amino-9-ethyl-carbazole visualization. A much wider and more abundant distribution of CHAT-I structures in the lower brain stem was demonstrated than in earlier studies. The following areas were newly identified as areas rich in CHAT-I fibers: the interpeduncular nucleus, medial geniculate body, central gray matter of pons, pontine nucleus, parabigeminal nucleus, dorsal tegmental nucleus of Gudden, lateral trapezoid nucleus, inferior colliculus, dorsal and ventral cochlear nuclei, medial and lateral vestibular nuclei, reticular formation of medulla oblongata, and gelatinosa of caudal trigeminal spinal tract nucleus. In addition to the areas in which they have been known to exist, CHAT-I perikarya were found in the caudal portion of substantia nigra pars reticulata, the area between trigeminal motor nucleus and superior olivary nucleus, the medial and spinal vestibular nucleus, prepositus hypoglossal nucleus, raphe magnus and obscurus, ventromedial portion of solitary tract nucleus and its just ventral reticular formation, and caudal trigeminal spinal tract nucleus.     

Localization of met-enkephalin-like immunoreactivity within pain-related nuclei of cervical spinal cord, brainstem and midbrain in the cat

Met-enkephalin immunoreactivity was investigated with an indirect immunoperoxidase technique in the cervical spinal cord, brainstem and midbrain of the cat, paying special attention to pain-related nuclei. Different technical conditions were used to reveal preferentially met-enkephalin-containing fibres and terminals or perikarya. Immunoreactive fibres and terminals were revealed optimally in sections from control animals incubated with detergent (Triton X-100). Immunoreactive perikarya were revealed in colchicine treated animals. Comparison between different routes of administration showed that local injections of colchicine are needed to reveal optimally immunoreactive perikarya in nuclei located far from the ventricles. Met-enkephalin-containing fibres and terminals are widely distributed in the posterior brain and spinal cord. The densest network of immunoreactive fibres are observed in the superficial layers of the cervical spinal cord and the caudal trigeminal nucleus, in the nucleus of the solitary tract, the nucleus of the facial nerve, the nucleus of the prepositus hypoglossi, the nucleus raphe pallidus, the medial vestibular nucleus, the interpedoncular nucleus and the substantia nigra. A moderate staining of fibres is observed in various nuclei including the ventral horn of the spinal cord and caudal trigeminal nucleus, the brainstem and midbrain reticular formation, the inferior olivary complex, the nucleus of the descending trigeminal tract and the periaqueductal grey. Met-enkephalin-containing perikarya are present in all the nuclei cited before, except in the inferior olivary complex. The densest aggregation of enkephalin-like perikarya is observed in the nucleus raphe magnus, nucleus raphe obscurus, nucleus raphe pallidus, nucleus reticularis gigantocellularis pars α and nucleus reticularis lateralis. The general distribution of enkephalin-containing structures in the cervical spinal cord, brainstem and midbrain of the cat appears very similar to that of the rat except in the substantia nigra where met-enkephalin cell bodies are found in the cat but not in the rat. In particular the pain-related nuclei present a similar distribution of the peptide in the two species; however, met-enkephalin-containing cell bodies are much more numerous in the cat than in the rat (notably in the reticular formation). Similar types of metenkephalin innervation occur in the dorsal and intermediate grey of the spinal cord and of the caudal trigeminal nucleus supporting further that the functional organizations of these regions are closely related.     

Distribution of protein kinase C-like immunoreactive neurons in rat brain

Distribution of protein kinase C in the CNS of rat is presented based on immunohistochemical analysis with monoclonal antibodies against this protein kinase. Protein kinase C-like immunoreactivity was discretely localized and associated with neurons. Most, if not all, glial cells were not significantly stained. The greatest density of the immunoreactive material was seen in the following regions: the olfactory bulb (external plexiform layer), olfactory tuberculum, anterior olfactory nucleus, cerebral cortex (layers I and IV), pyriform cortex, hippocampus (strata radiatum and oriens), amygdaloid complex (central and basolateral nuclei), cerebellar cortex (molecular layer), dorsal cochlear nucleus, nucleus spinal tract of the trigeminal nerve, and dorsal horn of the spinal cord (substantia gelatinosa). Image analysis revealed that the regional distribution of the protein kinase C-like immunoreaction generally agreed with that of phorbol ester-binding sites. Immunoreactive perikarya were found in the following areas: the cerebral cortex (layers V and VI), caudate putamen, hippocampus, thalamus, amygdaloid complex, medial and lateral geniculate nucleus, superior colliculus, cerebellar cortex, nucleus spinal tract of the trigeminal nerve, dorsal cochlear nucleus, and dorsal horn of the spinal cord. Intense protein kinase C-like immunoreactivity in the neuron was observed both in the membrane and cytoplasm of the perikarya, dendrites, axons, and axon terminals, while weak immunoreaction was seen in the nuclei but almost never in the nucleoles. A map of protein kinase C-containing neurons was constructed. Such an uneven distribution in the brain suggests that this enzyme may play roles in controlling neuronal function in the areas noted.     

Projections from the rhomboid nucleus of the bed nuclei of the stria terminalis: implications for cerebral hemisphere regulation of ingestive behaviors

The basic organization of an exceptionally complex pattern of axonal projections from one distinct cell group of the bed nuclei of the stria terminalis, the rhomboid nucleus (BSTrh), was analyzed with the PHAL anterograde tract-tracing method in rats. Brain areas that receive a strong to moderate input from the BSTrh fall into nine general categories: central autonomic control network (central amygdalar nucleus, descending hypothalamic paraventricular nucleus, parasubthalamic nucleus and dorsal lateral hypothalamic area, ventrolateral periaqueductal gray, lateral parabrachial nucleus and caudal nucleus of the solitary tract, dorsal motor nucleus of the vagus nerve, and salivatory nuclei), gustatory system (rostral nucleus of the solitary tract and medial parabrachial nucleus), neuroendocrine system (periventricular and paraventricular hypothalamic nuclei, hypothalamic visceromotor pattern generator network), orofaciopharyngeal motor control (rostral tip of the dorsal nucleus ambiguus, parvicellular reticular nucleus, retrorubral area, and lateral mesencephalic reticular nucleus), respiratory control (lateral nucleus of the solitary tract), locomotor or exploratory behavior control and reward prediction (nucleus accumbens, substantia innominata, and ventral tegmental area), ingestive behavior control (descending paraventricular nucleus and dorsal lateral hypothalamic area), thalamocortical feedback loops (medial-midline-intralaminar thalamus), and behavioral state control (dorsal raphé and locus coeruleus). Its pattern of axonal projections and its position in the basal telencephalon suggest that the BSTrh is part of a striatopallidal differentiation involved in modulating the expression of ingestive behaviors, although it may have other functions as well.     

Localization of preproenkephalin mRNA in the rat brain and spinal cord by in situ hybridization

To determine the localization in rat brain and spinal cord of individual neurons that contain the messenger RNA coding for the opioid peptide precursor preproenkephalin, we performed in situ hybridization with a tritiated cDNA probe complementary to a protion of preproenkephalin mRNA. We observed autoradiographic signal over the cytoplasm of neurons of many regions of the central nervous system. Several types of controls indicated specificity of the labeling. Neurons containing preproenkephalin mRNA were found in the piriform cortex, ventral tenia tecta, several regions of the neocortex, nucleus accumbens, olfactory tubercle, caudate-putamen, lateral septum, bed nucleus of the stria terminalis, diagonal band of Broca, preoptic area, amygdala (especially central nucleus, with fewer labeled neurons in all other nuclei), hippocampal formation, anterior hypothalamic nucleus, perifornical region, lateral hypothalamus, paraventricular nucleus, dorsomedial and ventromedial hypothalamic nuclei, arcuate nucleus, dorsal and ventral premamillary nuclei, medial mamillary nucleus, lateral geniculate nucleus, zona incerta, periaqueductal gray, midbrain reticular formation, ventral tegmental area of Tsai, inferior colliculus, dorsal and ventral tegmental nuclei of Gudden, dorsal and ventral parabrachial nuclei, pontine and medullary reticular formation, several portions of the raphe nuclei, nucleus of the solitary tract, nucleus of the spinal trigeminal tract (especially substantia gelatinosa), ventral and dorsal cochlear nuclei, medial and spinal vestibular nuclei, cuneate and external cuneate nuclei, gracile nucleus, superior olive, nucleus of the trapezoid body, some deep cerebellar nuclei, Golgi neurons in the cerebellum, and most laminae of the spinal cord. In most of these brain regions, the present results indicate that many more neurons contain preproenkephalin mRNA than have been appreciated previously on the basis of immunocytochemistry.     

Central projections of cervical primary afferent fibers in the guinea pig: an HRP and WGA/HRP tracer study

The central course and the projections of the first and the second cervical dorsal root ganglia and of suboccipital muscle primary afferent fibers in the guinea pig were studied by means of anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA/HRP) or aqueous solution of horseradish peroxidase (HRP). Injections of WGA/HRP into the second cervical dorsal root ganglion produced labeling in the dorsal and ventral horns. Within the spinal cord, the largest amount of HRP reaction product was found within the lateral third of the substantia gelatinosa and within the central cervical nucleus. The main area of termination in the medulla was the external cuneate nucleus. However, HRP reaction product was also found within the medial and inferior vestibular nuclei, cell group x, the perihypoglossal nuclei, the nucleus of the solitary tract, and the nucleus of the spinal trigeminal tract. Descending fibers could be detected as caudal as spinal segment T5. Injections of WGA/HRP into the first cervical dorsal root ganglion produced heavy terminal label within the central cervical nucleus but not within the substantia gelatinosa. Again, the external cuneate nucleus was the main area of termination within the medulla. Label could not be observed within the vestibular nuclear complex or within the spinal trigeminal nucleus. Injections of aqueous HRP into the suboccipital muscles produced heavy transganglionic label within the central cervical nucleus, whereas the substantia gelatinosa totally lacked terminal label. Ascending proprioceptive fibers reached the external cuneate nucleus and group x. Scanty projections could be detected within the vestibular nuclei as well as within the perihypoglossal nuclei except for the nucleus prepositus hypoglossi. Label was absent in the spinal trigeminal nucleus.     

Distribution of galaninergic immunoreactivity in the brain of the mouse

The distribution of galaninergic immunoreactive (-ir) profiles was studied in the brain of colchicine-pretreated and non-pretreated mice. Galanin (GAL)-ir neurons and fibers were observed throughout all encephalic vesicles. Telencephalic GAL-ir neurons were found in the olfactory bulb, cerebral cortex, lateral and medial septum, diagonal band of Broca, nucleus basalis of Meynert, bed nucleus of stria terminalis, amygdala, and hippocampus. The thalamus displayed GAL-ir neurons within the anterodorsal, paraventricular, central lateral, paracentral, and central medial nuclei. GAL-ir neurons were found in several regions of the hypothalamus. In the midbrain, GAL-ir neurons appeared in the pretectal olivary nucleus, oculomotor nucleus, the medial and lateral lemniscus, periaqueductal gray, and the interpeduncular nucleus. The pons contained GAL-ir neurons within the dorsal subcoeruleus, locus coeruleus, and dorsal raphe. In the medulla oblongata, GAL-ir neurons appear in the anterodorsal and dorsal cochlear nuclei, salivatory nucleus, A5 noradrenergic cells, gigantocellular nucleus, inferior olive, solitary tract nucleus, dorsal vagal motor and hypoglossal nuclei. Only GAL-ir fibers were seen in the lateral habenula nucleus, substantia nigra, parabrachial complex, cerebellum, spinal trigeminal tract, as well as the motor root of the trigeminal and facial nerves. GAL-ir was also observed in several circumventricular organs. The widespread distribution of galanin in the mouse brain suggests that this neuropeptide plays a role in the regulation of cognitive and homeostatic functions.     

Distribution of alpha 2 agonist binding sites in the rat and human central nervous system: analysis of some functional, anatomic correlates of the pharmacologic effects of clonidine and related adrenergic agents

Using [3H]para-aminoclonidine, alpha 2 adrenergic binding sites have been mapped in the rat and human CNS using in vitro labeling autoradiographic techniques. In both the rat and human thoracic spinal cord, high densities of alpha 2 binding sites were associated with the substantia gelatinosa and the intermediolateral cell column. In the rat medulla, high binding site density was observed in the medial nucleus of the solitary tract, dorsal motor nucleus of the vagus, raphe pallidus and the substantia gelatinosa of the trigeminal nucleus, while lower levels of specific binding were found in the lateral and ventrolateral medulla. In the human, a similar distribution was observed. However, significantly lower levels of specific binding were seen in the medial nts as opposed to the dmv. In the rat, high levels of specific binding were seen at pontine and midbrain levels in the locus coeruleus, parabrachial nucleus and periaqueductal gray. In the forebrain, several hypothalmic and limbic regions, including the paraventricular and arcuate nuclei of the hypothalamus, the central, medial and basal nuclei of the amygdala, lateral septum and bed nucleus of the stria terminalis and pyriform, entorhinal and insular cortex were labeled. Each of these regions are involved in either modulating autonomic functions directly or integrating somatosensory and/or affective function with autonomic mechanisms. Further, these regions are interrelated by reciprocal connections, and neurons that utilize noradrenaline or adrenaline as their neurotransmitter form a vital part of these connections. Thus, these functional, anatomical and neurochemical correlates of the alpha 2 binding site distribution establish a neurological basis for the complex pharmacological effects of centrally acting alpha 2 agonists.     

Efferent connections of the subfascicular area of the mesodiencephalic junction and its possible involvement in stimulation-produced analgesia

Stimulation-produced analgesia (SPA) can be induced in animals and humans from an ill-defined area of the mesodiencephalic junction lying beneath the parafascicular complex of the medial thalamus. Neurons projecting to the spinal cord, the subnucleus caudalis of the trigeminal complex, the nuclei raphé magnus and dorsalis, the inferior olivary complex and the amygdala could be observed in this area, using the retrograde transport of wheat germ agglutinin conjugated to horseradish peroxidase. On the basis of the locations of the neurons projecting to these different areas, 3 subnuclei were delineated: the rostral interstitial nucleus of the MLF lying laterally along the medial tip of the medial lemniscus, containing a few neurons projecting to the raphé nuclei and the inferior olivary complex; the subparafascicular nucleus (spf) lying medially in the rostralmost part of the area and containing neurons projecting to the amygdala and basal ganglia; the subfascicular area of the mesodiencephalic junction lying medially and caudal to the spf and containing neurons projecting to the raphé nuclei, the inferior olive, the caudalis subnucleus of the trigeminal complex and the spinal cord. The possibility that the subfascicular area of the mesodiencephalic junction is the effective site for SPA is discussed.     

Basic organization of projections from the oval and fusiform nuclei of the bed nuclei of the stria terminalis in adult rat brain.

The organization of axonal projections from the oval and fusiform nuclei of the bed nuclei of the stria terminalis (BST) was characterized with the Phaseolus vulgaris-leucoagglutinin (PHAL) anterograde tracing method in adult male rats. Within the BST, the oval nucleus (BSTov) projects very densely to the fusiform nucleus (BSTfu) and also innervates the caudal anterolateral area, anterodorsal area, rhomboid nucleus, and subcommissural zone. Outside the BST, its heaviest inputs are to the caudal substantia innominata and adjacent central amygdalar nucleus, retrorubral area, and lateral parabrachial nucleus. It generates moderate inputs to the caudal nucleus accumbens, parasubthalamic nucleus, and medial and ventrolateral divisions of the periaqueductal gray, and it sends a light input to the anterior parvicellular part of the hypothalamic paraventricular nucleus and nucleus of the solitary tract. The BSTfu displays a much more complex projection pattern. Within the BST, it densely innervates the anterodorsal area, dorsomedial nucleus, and caudal anterolateral area, and it moderately innervates the BSTov, subcommissural zone, and rhomboid nucleus. Outside the BST, the BSTfu provides dense inputs to the nucleus accumbens, caudal substantia innominata and central amygdalar nucleus, thalamic paraventricular nucleus, hypothalamic paraventricular and periventricular nuclei, hypothalamic dorsomedial nucleus, perifornical lateral hypothalamic area, and lateral tegmental nucleus. Moderately dense inputs are found in the parastrial, tuberal, dorsal raphé, and parabrachial nuclei and in the retrorubral area, ventrolateral division of the periaqueductal gray, and pontine central gray. Light projections end in the olfactory tubercle, lateral septal nucleus, posterior basolateral amygdalar nucleus, supramammillary nucleus, and nucleus of the solitary tract. These and other results suggest that the BSTov and BSTfu are basal telencephalic parts of a circuit that coordinates autonomic, neuroendocrine, and ingestive behavioral responses during stress.     

Three bulbospinal pathways from the rostral medulla of the cat: an autoradiographic study of pain modulating systems

Small amounts of ³H-leucine were injected into discrete regions in the rostral medulla of the cat. Descending projections from these sites were studied with autoradiographic methods. On the basis of differential projections to the medulla and spinal cord, three distinct regions were delineated. Nucleus reticularis gigantocellularis (Rgc), located dorsally in the medullary reticular formation, projects primarily to “motor” related sites, including cranial motor nuclei VI, VII, XII, nucleus intercalatus, and a part of the ipsilateral medial accessory olive. The projection to the spinal cord is primarily via the ipsilateral ventrolateral and contralateral ventral funiculi. The Rgc terminal field is in lamina VII and VIII ipsilateral and lamina VIII contralateral to the injection site. In contrast, nucleus raphe magnus, (NRM) located ventrally, in the midline of the rostral medulla projects primarily to structures with known nociceptive and/or visceral afferent input. These sites include the solitary nucleus, the dorsal motor nucleus (X) and the marginal and gelatinous layers of the spinal trigeminal nucleus caudalis. The projection to the spinal cord is bilateral, via the dorsolateral funiculus. Terminal fields are found in the marginal zone and the substantia gelatinosa of the dorsal horn, and more deeply in lamina V, medial VI and VII. Nucleus reticularis magnocellularis (Rmc), located lateral to NRM and ventral to Rgc, has an overlapping projection with NRM, but the projection is ipsilateral. This difference between Rmc and Rgc is correlated with cytoarchitectural features of the two regions. The possibility that the raphe-spinal pathway in the DLF mediates opiate and brain stimulation-produced analgesia is discussed.     

Distribution of choline acetyltransferase immunoreactive axons and terminals in the rat and ferret brainstem.

A survey was made of the density of the cholinergic innervation of different parts of the brainstem of the rat and ferret. Sections of rat and ferret brainstems were stained for choline acetyltransferase (ChAT) immunoreactivity by using a sensitive immunocytochemical method. Adjacent sections were stained for acetylcholinesterase activity or Nissl substance. The density of the distribution of fine calibre, varicose ChAT-positive axons, assumed to represent cholinergic terminals, was categorised arbitrarily into high, medium, or low. A high density of ChAT-positive terminals was found in all or parts of these structures: interpeduncular nucleus, superficial grey layer of the superior colliculus (ferret), intermediate layers of the superior colliculus, lateral part of the central grey (rat), an area medial to the parabigeminal nucleus (rat), pontine nuclei, ventral tegmental nucleus (rat), midline pontine reticular formation, and an area ventral to the exit point of the 5th nerve (ferret). A medium density of ChAT-positive terminals was observed in all or parts of: the substantia nigra zona compacta (ferret), ventral tegmental area (ferret), superficial grey layer of the superior colliculus, intermediate and deep layers of the superior colliculus, lateral central grey, area medial to the parabigeminal nucleus, inferior colliculus, dorsal tegmental nucleus, ventral tegmental nucleus (ferret), pontine nuclei, ventral nucleus of the lateral lemniscus (ferret), midline pontine reticular formation, ventral cochlear nucleus, dorsal cochlear nucleus, lateral superior olive, spinal trigeminal nuclei, prepositus hypoglossal nucleus, lateral reticular nucleus, paragigantocellular nucleus, and the dorsal column nuclei including the cuneate, external cuneate, and gracile nuclei. A low density of ChAT-positive terminals was seen throughout the remainder of the brainstem of the rat and ferret, but these terminals were absent from the medial superior olive, substantia nigra zona reticulata (rat), and the central part of the ferret lateral superior olive. A pericellular-like distribution of ChAT-positive terminals was observed in the ventral cochlear nucleus and in association with some of the cells of the nucleus of the mesencephalic tract of the trigeminal nerve. A climbing fibre type arrangement of ChAT-positive terminals was found in the substantia nigra zona compacta (ferret) and medial reticular formation. In general, the distribution of staining for AChE activity reflected that of the distribution of ChAT immunoreactivity in the brainstem, except in a few regions where there were also species differences in the distribution of ChAT-positive terminals, e.g., in the superficial grey layer of the superior colliculus and in the substantia nigra.(ABSTRACT TRUNCATED AT 400 WORDS)     

Somatostatin receptors: distribution in rat central nervous system and human frontal cortex

Somatostatins are a brain peptide family centered on a 14-amino acid cyclic peptide (SS-14) and a 28-amino acid N-terminally extended form (SS-28). Using radioiodinated analogs of SS-14 and SS-28, we have identified specific binding sites in rat and human brain sections that display pharmacological properties anticipated for somatostatin receptors and discrete patterns of anatomical localization. High binding densities are found in many forebrain regions, with special densities in infragranular cerebral cortical laminae in rat and human brain. In the rat, other densities lie in olfactory zones, lateral and triangular septal nuclei, the CA-1 hippocampal region, and claustrum with moderate densities in the striatum. Discrete hypothalamic areas, especially the median preoptic, paraventricular, and periventricular nuclei, display elevated binding levels, while the thalamus shows only scattered areas of modest binding. Midbrain receptor concentrations are found in portions of the periaqueductal gray, interpeduncular nucleus, and the substantia nigra. Notable pontine and medullary densities lie in the locus coeruleus, fourth ventricular floor, parabrachial, solitary, prepositus hypoglossal, dorsal column, and caudal trigeminal zones. Although the cerebellar cortex shows unimpressive densities, each of the deep cerebellar nuclei is heavily labeled. Modest spinal cord receptor densities are concentrated in the substantia gelatinosa and central cord regions. These localizations show many parallels with the distributions of SS-immunoreactive neurons, fibers, and terminals determined previously by immunohistochemistry. They provide plausible loci for several reported physiological or pharmacological activities of the SS-peptides, and may improve understanding of the role of the SS alterations described in several human neurodegenerative disorders.     

Immunohistochemical localization of a melanin concentrating hormone-like peptide in the rat brain

Using antisera generated in rabbits against salmon melanin concentrating hormone (MCH) coupled to human thyroglobulin, the distribution of MCH-like immunoreactivity was mapped throughout the rat central nervous system. The distribution of MCH-like immunoreactivity in rat brain is unique and different from the distribution of other neuropeptides. MCH-like immunoreactive perikarya and fibers are predominant in the posterior hypothalamic area, mostly in the medial forebrain bundle-lateral hypothalamic area subzona incerta and the perifornical area. Cell bodies are located mainly in the medial forebrain bundle and in proximity to well defined hypothalamic nuclei. Fibers are seen throughout the rat brain in all neocortical areas, the neostriatum and the amygdala, in the diencephalon in most hypothalamic nuclei, the habenula, the mamillary body and very dense in the medial forebrain bundle and just ventral to the zona incerta ("subzona incerta"). In the mesencephalon there are fibers in the central gray; in the pons-medulla fibers are contained in the dorsal and ventral parabrachial nuclei; in the tegmental area ventral to the fourth ventricle; in the spinal trigeminal area, the substantia gelatinosa and the reticular nuclei. In the spinal cord there are more fibers in the dorsal than in the ventral horn. The posterior pituitary also contained few MCH-like fibers. It is suggested that a peptide similar, but not identical, to salmon MCH is present in the rat central nervous system.     

Organization of the projections of a circumventricular organ: the area postrema in the rat

The projections of the rat area postrema were analysed using anterograde and retrograde axonal transport techniques. Discrete injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) into the area postrema produced anterograde labeling in specific medullary and pontine nuclei. In the medulla, anterograde labeling was present in the internal solitary zone and dorsal division of the medial solitary nucleus, both of which also contained a small number of retrogradely labeled perikarya. Prominent projections to the dorsal motor nucleus of the vagus were seen only if the WGA-HRP injections in the area postrema invaded dorsal solitary nuclei. In the pons, anterograde labeling was present in the parabrachial nuclei, the dorsolateral tegmental nucleus, and the pericentral division of the dorsal tegmental nucleus. By far the major pontine projection was to the dorsolateral region of the middle one-third of the rostrocaudal extent of the parabrachial nuclei. Retrograde fluorescent tracing studies indicated that most area postrema neurons take part in this parabrachial projection. The area postrema projection to the parabrachial nuclei was bilaterally distributed, whereas that from the dorsal solitary nuclei was primarily ipsilateral. The external solitary zone, immediately subadjacent to the area postrema, neither received area postrema projections nor participated in the projections to the parabrachial nuclei. Fluorescent retrograde double labeling studies confirmed the bilateral nature of the area postrema projection to the parabrachial nuclei. In addition, because no doubly labeled neurons were observed it appears that individual area postrema neurons project to either side but not both sides of the dorsal pons. Thus, numerous neuronal pathways exist for the transfer of blood-borne information (that cannot cross the blood-brain barrier) from the area postrema to other brain regions.     

Immunohistochemical studies of FMRF-amide-like immunoreactivity in rat brain

The anatomical distribution of neuronal perikarya and nerve fibres containing FMRF-amide-like immunoreactivity in the brain, spinal cord and pituitary of the rat has been studied by immunohistochemistry. In animals pretreated with colchicine, the highest concentration of nerve cell bodies occurred in hypothalamic nuclei. Cells were also present in the cortex, striatum, septum, thalamus and in the brainstem. Beaded nerve fibres were abundant in the septum, nucleus of the striae terminalis, hypothalamus, medial regions of the thalamus, the parabrachial nucleus, the ventrolateral medulla, the substantia gelatinosa of the spinal trigeminal nucleus and the dorsal horn of the spinal cord. Fibres were also present in the cortex, striatum, amygdala, pons, ventral spinal cord and the neural lobe of the pituitary. The localization was specific in that preabsorbtion of the antisera with FMRF-amide, but not structurally related molecules such as Met-Enk-Arg6Phe7, APP or BPP, completely abolished the localization. The mammalian counterparts of FMRF-amide may have a neurotransmitter or neuromodulatory role.     

Mu,delta, and kappa opioid receptor mRNA expression in the rat CNS: An in situ hybridization study

The μ, δ, and κ opioid receptors are the three main types of opioid receptors round in the central nervous system (CNS) and periphery. These receptors and the peptides with which they interact are important in a number of physiological functions, including analgesia, respiration, and hormonal regulation. This study examines the expression of μ, δ, and κ receptor mRNAs in the rat brain and spinal cord using in situ hybridization techniques. Tissue sections were hybridized with ³⁵S-labeled cRNA probes to the rat μ (744–1, 064 b), δ (304–1,287 b), and κ (1,351–2,124 b) receptors. Each mRNA demonstrates a distinct anatomical distribution that corresponds well to known receptor binding distributions. Cells expressing μ receptor mRNA are localized in such regions as the olfactory bulb, caudate-putamen, nucleus accumbens, lateral and medial septum, diagonal band of Broca, bed nucleus of the stria terminalis, most thalamic nuclei, hippocampus, amygdala, medial preoptic area, superior and inferior colliculi, central gray, dorsal and median raphe, raphe magnus, locus coeruleus, parabrachial nucleus, pontine and medullary reticular nuclei, nucleus ambiguus, nucleus of the solitary tract, nucleus gracilis and cuneatus, dorsal motor nucleus of vagus, spinal cord, and dorsal root ganglia. Cellular localization of δ receptor mRNA varied from μ or κ, with expression in such regions as the olfactory bulb, allo- and neocortex, caudate-putamen, nucleus accumbens, olfactory tubercle, ventromedial hypothalamus, hippocampus, amygdala, red nucleus, pontine nuclei, reticulotegmental nucleus, motor and spinal trigeminal, linear nucleus of the medulla, lateral reticular nucleus, spinal cord, and dorsal root ganglia. Cells expressing, κ receptor mRNA demonstrate a third pattern of expression, with cells localized in regions such as the claustrum, endopiriform nucleus, nucleus accumbens, olfactory tubercle, medial preoptic area, bed nucleus of the stria terminalis, amygdala, most hypothalamic nuclei, median eminence, infundibulum, substantia nigra, ventral tegmental area, raphe nuclei, paratrigeminal and spinal trigeminal, nucleus of the solitary tract, spinal cord, and dorsal root ganglia. These findings are discussed in relation to the physiologica functions associated with the opioid receptors.     

Distribution of the P2X2 receptor subunit of the ATP-gated ion channels in the rat central nervous system

The distribution of the P2X2 receptor subunit of the adenosine 5'-triphosphate (ATP)-gated ion channels was examined in the adult rat central nervous system (CNS) by using P2X2 receptor-specific antisera and riboprobe-based in situ hybridisation. P2X2 receptor mRNA expression matched the P2X2 receptor protein localisation. An extensive expression pattern was observed, including: olfactory bulb, cerebral cortex, hippocampus, habenula, thalamic and subthalamic nuclei, caudate putamen, posteromedial amygdalo-hippocampal and amygdalo-cortical nuclei, substantia nigra pars compacta, ventromedial and arcuate hypothalamic nuclei, supraoptic nucleus, tuberomammillary nucleus, mesencephalic trigeminal nucleus, dorsal raphe, locus coeruleus, medial parabrachial nucleus, tegmental areas, pontine nuclei, red nucleus, lateral superior olive, cochlear nuclei, spinal trigeminal nuclei, cranial motor nuclei, ventrolateral medulla, area postrema, nucleus of solitary tract, and cerebellar cortex. In the spinal cord, P2X2 receptor expression was highest in the dorsal horn, with significant neuronal labeling in the ventral horn and intermediolateral cell column. The identification of extensive P2X2 receptor immunoreactivity and mRNA distribution within the CNS demonstrated here provides a basis for the P2X receptor antagonist pharmacology reported in electrophysiological studies. These data support the role for extracellular ATP acting as a fast neurotransmitter at pre- and postsynaptic sites in processes such as sensory transmission, sensory-motor integration, motor and autonomic control, and in neuronal phenomena such as long-term potentiation (LTP) and depression (LTD). Additionally, labelling of neuroglia and fibre tracts supports a diverse role for extracellular ATP in CNS homeostasis.