Functional and anatomical organization of cardiovascular pressor and depressor sites in the lateral hypothalamic area: I. Descending projections.

The present study describes the anatomical organization of projections from functionally defined cell groups of the lateral hypothalamic area. Cardiovascular pressor and depressor sites were identified following microinjection (5-50 nl) of 0.01-1.0 M L-glutamate or D,L-homocysteate into the anesthetized rat. Subsequent injections of Phaseolus vulgaris-leucoagglutinin (PHA-L) or wheat germ agglutinin-horseradish peroxidase (WGA-HRP) were made into pressor or depressor sites and their connections with the brainstem and spinal cord were traced. Decreases in blood pressure (10-45 mmHg) and heart rate (20-70 bpm) were elicited from tuberal (LHAt) and posterior (LHAp) regions of the lateral hypothalamic area (LHA). Depressor neurons in the LHAt have descending projections to the central gray, dorsal and median raphe nuclei, pedunculopontine tegmental nucleus, pontine reticular formation, medial and lateral parabrachial nuclei, laterodorsal tegmental region, and medullary reticular formation including the region of the lateral tegmental field, nucleus ambigous, and rostrocaudal ventral lateral medulla. In contrast, descending projections from depressor neurons in the LHAp have dense terminal fields in the rostral, middle, and commissural portions of the nucleus of the solitary tract and the lateral tegmental field as well as the ventrolateral central gray, pedunculopontine tegmental nucleus, and medial and lateral parabrachial nuclei. Both the LHAt and LHAp have light projections to the intermediate region of the cervical and thoracic spinal cord. Increases in blood pressure (10-40 mmHg) and heart rate (20-70 bpm) were elicited almost exclusively from neurons located medial to the LHAt and LHAp in a region surrounding the fornix, termed the perifornical area (PFA). Pressor cells in the PFA have descending projections to the central gray, dorsal and median raphe nuclei, laterodorsal tegmental nucleus, and Barrington's nucleus as well as a light projection to the commissural portion of the nucleus of the solitary tract and the intermediate region of the cervical and thoracic spinal cord. The retrograde labeling observed in the WGA-HRP studies indicates that cells in most terminal fields have reciprocal projections to the pressor and depressor regions of the LHA. The results demonstrate that groups of neurons in the lateral hypothalamus with specific cardiovascular function have differential projections to the brain stem.     

Corticotropin releasing factor-like immunoreactivity in the rat brain as revealed by a modified cobalt-glucose oxidase-diaminobenzidine method

A cobalt-glucose-oxidase diaminobenzidine (Co-GOD) method, employing a specific antiserum against rat corticotropin releasing factor (CRF), was applied to determine immunohistochemically a widespread and detailed localization of corticotropin releasing factor-like immunoreactivity (CRFI) in the rat brain. Besides the CRFI cells in the paraventricular hypothalamic nucleus that project to the median eminence, CRFI cells were demonstrated in many brain regions, including the olfactory bulb, cerebral cortex, septal nuclei, hippocampus, amygdala, thalamic nuclei, medial hypothalamic nuclei, lateral hypothalamic area, perifornical area, central gray, cuneiform nucleus, inferior colliculus, raphe nuclei, mesencephalic reticular formation, laterodorsal tegmental nucleus, locus coeruleus, parabrachial nuclei, mesencephalic tract of the trigeminal nerve, pontine reticular formation, lateral superior olive, vestibular nuclei, prepositus hypoglossal nucleus, nucleus of the solitary tract, dorsal motor nucleus of the vagus, lateral reticular nucleus, nucleus of the spinal tract of the trigeminal nerve, external cuneate nucleus, inferior olive, and medullary reticular formation. CRFI-reacting neural processes were also detected in these same areas. In particular, the median eminence, lateral septum, bed nucleus of the stria terminalis, mesencephalic reticular formation, parabrachial nuclei, and nucleus of the solitary tract contained large numbers of CRFI fibres. The widespread localization of CRFI demonstrated in the present study strongly suggests that CRF, like many other neurohormones and peptides, may act as a neurotransmitter and/or neuromodulator in numerous extrahypothalamic circuits, as well as participate in neuroendocrine regulation.     

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.     

Experimental study of the projections of the nucleus of the tractus solitarius and the area postrema in the cat

Projections from the area postrema and adjacent parts of the medial solitary nucleus are demonstrated with the Nauta method following lesions limited exclusively to these structures. Experiments are controlled with lesions involving adjacent bulbar regions, cerebellum, and spinal cord. Ascending pathways in the dorsal and lateral columns of the spinal cord project ipsilaterally to the area postrema and bilaterally to a para-alar nucleus in the ventral periphery of the nucleus gracilis. Neurons in the area postrema project mainly inspilaterally to the dorsal and medial regions of the medial solitary nucleus. Neurons in the posterior half of the medical solitary nucleus project ipsilaterally to the lateral solitary nucleus, dorsal vagal nucleus, ambigus, retrofacial nucleus, and dorsal and lateral bulbar reticular formation. Projections to nuclei intercalatus and prepositus hypoglossi, bilaterally, and to the ipsilateral dorsal tegmental nucleus by way of the dorsal longitudinal fasciculus are also shown. No direct projections to the diencephalon are demonstrated. Control lesions in the dorsal column nuclei reveal projections to the contralateral inferior olive and thalamic reticular and ventrobasal nuclei, but not to the projection sites of the solitary nucleus. Evidence is given to support the hypothesis that ascening visceral pathways are interruped in the bulbar reticular formation and dorsal tegmental nucleus before reaching the diencephalon. Correlations are suggested with functional aspects of the central autonomic and reticular activating systems.     

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)     

Postnatal development of preproenkephalin mRNA containing neurons in the rat lower brainstem

Postnatal developmental changes of preproenkephalin (PPE) gene expression in rat brainstem neurons were studied by in situ hybridization histochemistry. On the basis of PPE mRNA expression, brainstem neurons were categorized into three types: 1) type I neurons were characterized by constant or increasing expression of PPE mRNA during postnatal development; 2) type II neurons started to express PPE mRNA several days after birth and continued to do so thereafter; and 3) type III neurons showed transient expression of PPE mRNA or stopped expressing the mRNA during early postnatal development. Type I PPE neurons were observed in diverse brainstem structures including the mesencephalic and pontine central gray matter, various reticular and raphe nuclei, the ventral tegmental area of Tsai, the interpeduncular nucleus, the nucleus of the brachium of the inferior colliculus, the ventral and dorsal tegmental nuclei of Gudden, the sphenoid nucleus, the laterodorsal tegmental nucleus, Barrington's nucleus, the parabrachial region, the lateral lemniscus and its related nuclei, the trapezoid nucleus, the rostral and ventromedial periolivary nuclei, the mesencephalic trigeminal and principal sensory trigeminal nuclei, the locus coeruleus, the subcoeruleus nucleus, the medial and spinal vestibular nuclei, the dorsal and ventral cochlear nuclei, the medial and lateral cerebellar nuclei, the Roller nucleus, and the intermedius nucleus of the medulla. Type II PPE neurons were found in the superior colliculus, the inferior colliculus, the central part of the dorsal tegmental nucleus, and as Golgi neurons in the granular layer of the cerebellum. Type III PPE neurons were located in the substantia nigra, the red nucleus, the superior olive, the motor trigeminal nucleus, the facial nucleus, the inferior olive, the dorsal motor nucleus of the vagus, and the hypoglossal nucleus. Such region-specific expression of the PPE gene during postnatal ontogeny suggests that rat brainstem PPE neurons may be involved in a variety of developmental events, such as cell proliferation, differentiation, and migration.     

Opioid receptor-like (ORL1) receptor distribution in the rat central nervous system: comparison of ORL1 receptor mRNA expression with (125)I-[(14)Tyr]-orphanin FQ binding.

The recently discovered neuropeptide orphanin FQ (OFQ), and its opioid receptor-like (ORL1) receptor, exhibit structural features suggestive of the micro, kappa, and delta opioid systems. The anatomic distribution of OFQ immunoreactivity and mRNA expression has been reported recently. In the present analysis, we compare the distribution of orphanin receptor mRNA expression with that of orphanin FQ binding at the ORL1 receptor in the adult rat central nervous system (CNS). By using in vitro receptor autoradiography with (125)I-[(14)Tyr]-OFQ as the radioligand, orphanin receptor binding was analyzed throughout the rat CNS. Orphanin binding sites were densest in several cortical regions, the anterior olfactory nucleus, lateral septum, ventral forebrain, several hypothalamic nuclei, hippocampal formation, basolateral and medial amygdala, central gray, pontine nuclei, interpeduncular nucleus, substantia nigra, raphe complex, locus coeruleus, vestibular nuclear complex, and the spinal cord. By using in situ hybridization, cells expressing ORL1 mRNA were most numerous throughout multiple cortical regions, the anterior olfactory nucleus, lateral septum, endopiriform nucleus, ventral forebrain, multiple hypothalamic nuclei, nucleus of the lateral olfactory tract, medial amygdala, hippocampal formation, substantia nigra, ventral tegmental area, central gray, raphe complex, locus coeruleus, multiple brainstem motor nuclei, inferior olive, deep cerebellar nuclei, vestibular nuclear complex, nucleus of the solitary tract, reticular formation, dorsal root ganglia, and spinal cord. The diffuse distribution of ORL1 mRNA and binding supports an extensive role for orphanin FQ in a multitude of CNS functions, including motor and balance control, reinforcement and reward, nociception, the stress response, sexual behavior, aggression, and autonomic control of physiologic processes.     

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.     

Ontogeny of calcitonin receptor mRNA and protein in the developing central nervous system of the rat

In this study, the expression of receptors for calcitonin (CTR), the CTR C1a and C1b isoforms, was investigated during development of the fetal rat central nervous system (CNS) by using in situ hybridization and immunohistochemistry. Coincident expression with both techniques was evident. Immunohistochemical evidence for the expression of the C1a isoform alone was found. Expression was first observed at embryonic day 12/13 (E12/E13) within and adjacent to the ventricular zones known to include primary matrices of proliferation, in regions of the preoptic area, anterior and posterior hypothalamus, anterior and posterior pons, medulla, and spinal cord. At later times, with the decline in the density of immunoreactivity at these loci (E15), expression in primary matrices was found later at distinct loci within the ventricular zones of cerebellum (E17), and at E19, the tectum, lateral ventricle, and cortical subplate. By E19, the density of staining had increased and was widespread throughout the expanding CNS. In the rostral domains, moderate to high density was found in the external plexiform layer; the medial preoptic area and nucleus; the ventromedial, dorsomedial, and arcuate hypothalamic nuclei; and the lateral and posterior hypothalamic areas. In the midbrain, similar levels of expression were noted in the central nucleus of raphe; the deep mesencephalic, dorsal raphe, and laterodorsal tegmental nuclei; and the ventral periaqueductal gray. In the pons, positive loci included the locus coeruleus and the gigantocellular and pontine reticular nuclei. In the medulla, high expression was evident in the gigantocellular, intermediate, magnocellular, and medullary reticular, spinal trigeminal and cuneate nuclei; and the nucleus tractus solitarius. In the spinal cord, moderate to high density of staining was found in the ventral, dorsal, and lateral horns, and in the ventral, dorsal, and cuneate funiculi. On the other hand, transitory expression was found in the diagonal band, bed nucleus of the stria terminalis, amygdala, and the lateral mamillary and anterobasal nuclei of the hypothalamus. These studies indicate a role for CTR in the activation of some premigratory neuroblasts in the CNS as well as a possible role later in an undefined function associated with mature neurons of particular nuclei.     

Subcortical projections to the centromedian and parafascicular thalamic nuclei in the cat

The primary objective of this study is to identify the totality of input to the centromedian and parafascicular (CM-Pf) thalamic nuclear complex. The subcortical projections upon the CM-Pf complex were studied in the cat with three different retrograde tracers. The tracers used were unconjugated horseradish peroxidase (HRP), horseradish peroxidase conjugated to wheat germ agglutinin (WGA-HRP), and rhodamine-labeled fluorescent latex microspheres (RFM). Numerous subcortical structures or substructures contained labeled neurons with all three tracing techniques. These labeled structures included the central nucleus of the amygdala; the entopeduncular nucleus; the globus pallidus; the reticular and ventral lateral geniculate nuclei of the thalamus; parts of the hypothalamus including the dorsal, lateral, and posterior hypothalamic areas and the ventromedial and parvicellular nuclei; the zona incerta and fields of Forel; parts of the substantia nigra including the pars reticularis and pars lateralis, and the retrorubral area; the pretectum; the intermediate and deep layers of the superior colliculus; the periaqueductal gray; the dorsal nucleus of the raphe; portions of the reticular formation, including the mesencephalic, pontis oralis, pontis caudalis, gigantocellularis, ventralis, and lateralis reticular nuclei; the nucleus cuneiformis; the marginal nucleus of the brachium conjunctivum; the locus coeruleus; portions of the trigeminal complex, including the principal sensory and spinal nuclei; portions of the vestibular complex, including the lateral division of the superior nucleus and the medial nucleus; deep cerebellar nuclei, including the medial and lateral cerebellar nuclei; and lamina VII of the cervical spinal cord. Moreover, the WGA-HRP and rhodamine methods (known to be more sensitive than the HRP method) revealed several afferent sources not shown by HRP: the anterior hypothalamic area, ventral tegmental area, lateral division of the superior vestibular nucleus, nucleus interpositus, and the nucleus praepositus hypoglossi. Also, the rhodamine method revealed labeled neurons in laminae V and VI of the cervical spinal cord.     

Localization of GABAA-receptor alpha 1 subunit mRNA-containing neurons in the lower brainstem of the rat

The localization of gamma-aminobutyric acid-A (GABAA) receptors (GABAA-R) in the lower brainstem of the rat was examined by means of in situ hybridization histochemistry using an oligonucleotide probe to the sequence of the alpha 1 subunit (GABAA-R alpha 1). Strongly labeled neurons were found in the cranial motor nuclei, the dorsal motor nucleus of the vagus, reticular formation (large neurons), lateral vestibular nucleus, dorsal nucleus of the lateral lemniscus, central nucleus of the inferior colliculus, intermediate and white layers of the superior colliculus, red nucleus and substantia nigra. In addition, moderately labeled cells were abundant in the nucleus of the solitary tract, medial and inferior vestibular nuclei, parabrachial area, dorsal and ventral tegmental nuclei of Gudden, central gray matter, ventral nucleus of the lateral lemniscus, and reticular formation (small neurons). This study has therefore revealed some of the target neurons of GABA-containing fibers in the lower brainstem.     

Localization of orphanin FQ (nociceptin) peptide and messenger RNA in the central nervous system of the rat

Orphanin FQ (OFQ) is the endogenous agonist of the opioid receptor-like receptor (ORL-1). It and its precursor, prepro-OFQ, exhibit structural features suggestive of the opioid peptides. A cDNA encoding the OFQ precursor sequence in the rat recently has been cloned, and the authors recently generated a polyclonal antibody directed against the OFQ peptide. In the present study, the authors used in situ hybridization and immunohistochemistry to examine the distribution of OFQ peptide and mRNA in the central nervous system of the adult rat. OFQ immunoreactivity and prepro-OFQ mRNA expression correlated virtually in all brain areas studied. In the forebrain, OFQ peptide and mRNA were prominent in the neocortex endopiriform nucleus, claustrum, lateral septum, ventral forebrain, hypothalamus, mammillary bodies, central and medial nuclei of the amygdala, hippocampal formation, paratenial and reticular nuclei of the thalamus, medial habenula, and zona incerta. No OFQ was observed in the pineal or pituitary glands. In the brainstem, OFQ was prominent in the ventral tegmental area, substantia nigra, nucleus of the posterior commissure, central gray, nucleus of Darkschewitsch, peripeduncular nucleus, interpeduncular nucleus, tegmental nuclei, locus coeruleus, raphe complex, lateral parabrachial nucleus, inferior olivary complex, vestibular nuclear complex, prepositus hypoglossus, solitary nucleus, nucleus ambiguous, caudal spinal trigeminal nucleus, and reticular formation. In the spinal cord, OFQ was observed throughout the dorsal and ventral horns. The wide distribution of this peptide provides support for its role in a multitude of functions, including not only nociception but also motor and balance control, special sensory processing, and various autonomic and physiologic processes.     

Vasopressin and oxytocin systems in the brain and upper spinal cord of Macaca fascicularis

This paper describes the vasopressin (VP) and oxytocin (OXT) immunoreactive structures in the brain and upper spinal cord of the adult male and female Macaca fascicularis. Immunocytochemistry following intraventricular application of colchicine displayed VP neurons in the diagonal band of Broca (DBB), bed nucleus of the stria terminalis (BST), medial amygdaloid nucleus, dorsomedial hypothalamic nucleus, area of the locus coeruleus (LC), solitary tract nuclei (NTS), and the dorsal horn of the cervical spinal cord in addition to those known to exist in the paraventricular, supraoptic, and suprachiasmatic hypothalamic nuclei. Furthermore, a dense accumulation of VP fibers was observed in areas such as the DBB, medial septum, BST, amygdala, hippocampus, ventral tegmental area, periaquaductal gray, dorsal and ventral raphe, area of Forel, LC region, parabrachial nuclei, and NTS. The lateral septum and lateral habenula displayed no and very few VP fibers, respectively. No extrahypothalamic OXT neurons were found in the brain of this macaque monkey. Dense concentrations of OXT fibers were demonstrated in the amygdala, NTS, and marginal layer of the cervical spinal cord. No sexual dimorphism was found in this primate VP or OXT system. The results show a distribution of the central VP and OXT systems in this primate which is quite different from that in the rat. However, in various aspects it agrees with current data on the VP and OXT systems of the human brain. The present results suggest, therefore, that this monkey might serve as a better model for the human VP system than the rat.     

Efferent connections of the lateral hypothalamic area of the rat: An autoradiographic investigation

The efferent projections of the lateral hypothalamic area (LHA) at mid-tuberal levels were examined with the autoradiographic tracing method. Connections were observed to widespread regions of the brain, from the telencephalon to the medulla. Ascending fibers course through LHA and the lateral preoptic area and lie lateral to the diagonal band of Broca. Fibers sweep dorsally into the lateral septal nucleus, cingulum bundle and medial cortex. Although sparse projections are found to the ventromedial hypothalamic nucleus, a prominent pathway courses to the dorsal and medial parvocellular subnuclei of the paraventricular nucleus. Labeled fibers in the stria medullaris project to the lateral habenular nucleus. The central nucleus of the amygdala is encapsulated by fibers from the stria terminalis and the ventral amygdalofugal pathway. The substantia innominate, nucleus paraventricularis of the thalamus, and bed nucleus of the stria terminalis also receive LHA fibers. Three descending pathways course to the brainstem: (1) periventricular system, (2) central tegmental tract (CTT), and (3) medial forebrain bundle (MFB). Periventricular fibers travel to the ventral and lateral parts of the midbrain central gray, dorsal raphe nucleus, and laterodorsal tegmental nucleus of the pens. Dorsally coursing fibers of CTT enter the central tegmental field and the lateral and medial parabrachial nuclei. The intermediate and deep layers of the superior colliculus receive some fibers. Fibers from CTT leave the parabranchial region by descending in the ventrolateral pontine and medullary reticular formation; some of these fibers sweep dorsomedially into the nucleus tractus solitarius, dorsal motor nucleus of the vagus, and nucleus commissuralis. From MFB, fibers descend into the ventral tegmental area and to the border of the median raphe and raphe magnus nuclei.     

In situ hybridization analysis of the distribution of neurokinin-3 mRNA in the rat central nervous system

The tachykinin family of neuropeptides, which includes substance P, neurokinin A, and neurokinin B, have three distinct receptors; NK-1, NK-2, and NK-3. With the cloning of the rat NK-3 cDNA, it is now possible to evaluate the distribution of NK-3 mRNA in the rat brain. Female rat brains were sectioned and hybridized with a riboprobe complimentary to NK-3 mRNA. The results of these studies revealed an extensive distribution of NK-3 mRNA throughout the rostral-caudal extent of the brain, spinal cord, and retina. In agreement with previous binding studies, we observed NK-3 mRNA in the cortex, the amygdala, the hippocampus, the medial habenula, the zona incerta, the paraventricular and supraoptic nuclei of the hypothalamus, the substantia nigra, the ventral tegmental area, the interpeduncular nucleus, the raphe nuclei, the dorsal tegmental nucleus, and the nucleus of the solitary tract. In contrast with binding data, only a few NK-3 mRNA cells were detected in the striatum. In addition, the present study detected NK-3 mRNA in the olfactory bulb, the dentate gyrus and subiculum, the medial septum, the diagonal band of Broca, the ventral pallidum, the globus pallidus, the bed nucleus of the stria terminalis, the arcuate, the premammillary and mammillary nuclei, the dorsal and lateral regions of the posterior hypothalamus, the central gray, the cerebellum, the parabrachial nuclei, the nucleus of the spinal trigeminal tract, the dorsal horn of the spinal cord, and the retina. The results of these in situ hybridization histochemical studies have provided detailed and novel information about the distribution of NK-3 mRNA and have elucidated the putative sites of neurokinin B action in the rat central nervous system. © 1996 Wiley-Liss, Inc.     

Efferents from the medial anterior hypothalamic area in the guinea pig

Medial anterior hypothalamic connections were studied with H³-proline and autoradiography. Most of the axons projected to other hypothalamic nuclei. The major pathways were found ventral medial to the fornix and in the periventricular tract. Substantial projections were apparent in the ventromedial and dorsomedial nuclei with less label in the arcuate nucleus. The dorsal premammillary nuclei were labeled bilaterally, particularly with more caudal injections of anterior hypothalamus. Efferents were evident in the posterior hypothalamus and continued into the central gray of the midbrain. Labeled fibers reached the ventral tegmental area and in the reticular formation were traced only through pons. Rostral projections were to the medial and lateral preoptic areas and ventral lateral septum. The bed nucleus of stria terminalis was labeled and a very few fibers reached the medial amygdaloid nucleus. The periventricular nucleus of thalamus was labeled.     

Raphespinal and reticulospinal axon collaterals to the hypoglossal nucleus in the rat.

Neurons in the medial tegmental field project directly to spinal somatic motoneurons and to cranial motoneuron pools such as the hypoglossal nucleus. The axons of these neurons may be highly collateralized, projecting to multiple levels of the spinal cord and to many diverse regions at different levels of the neuraxis. We employed a double fluorescent retrograde tracer technique to examine whether medial tegmental neurons that project to the spinal cord also project to the hypoglossal nucleus. Injections of Diamidino Yellow into the hypoglossal nucleus and Fast Blue into the spinal cord produced large numbers of double labeled neurons in the medial tegmental field, particularly in the caudal raphe nuclei and adjacent ventromedial reticular formation. In these structures the number of neurons projecting to both the hypoglossal nucleus and the spinal cord was equivalent to the number of neurons projecting to multiple levels of the spinal cord observed in control animals. Fewer neurons projecting to both the hypoglossal nucleus and the spinal cord were observed in several other nuclei and subregions of the medial tegmental field, while almost no such neurons were observed in the lateral tegmental field or other pontomedullary structures. These results demonstrate that neurons of the caudal raphe nuclei and adjacent ventromedial reticular formation project to both the spinal cord and the hypoglossal nucleus, and support the concept that the diffuse projections to motoneuron pools from the medial tegmental field globally modulate both spinal and cranial somatic motoneuron excitability.     

Ascending projections from the area around the spinal cord central canal: A Phaseolus vulgaris leucoagglutinin study in rats.

A single small iontophoretic injection of Phaseolus vulgaris leucoagglutinin labels projections from the area surrounding the spinal cord central canal at midthoracic (T6-T9) or lumbosacral (L6-S1) segments of the spinal cord. The projections from the midthoracic or lumbosacral level of the medial spinal cord are found: 1) ascending ipsilaterally in the dorsal column near the dorsal intermediate septum or the midline of the gracile fasciculus, respectively; 2) terminating primarily in the dorsal, lateral rim of the gracile nucleus and the medial rim of the cuneate nucleus or the dorsomedial rim of the gracile nucleus, respectively; and 3) ascending bilaterally with slight contralateral predominance in the ventrolateral quadrant of the spinal cord and terminating in the ventral and medial medullary reticular formation. Other less dense projections are to the pons, midbrain, thalamus, hypothalamus, and other forebrain structures. Projections arising from the lumbosacral level are also found in Barrington's nucleus. The results of the present study support previous retrograde tract tracing and physiological studies from our group demonstrating that the neurons in the area adjacent to the central canal of the midthoracic or lumbosacral level of the spinal cord send long ascending projections to the dorsal column nucleus that are important in the transmission of second-order afferent information for visceral nociception. Thus, the axonal projections through both the dorsal and the ventrolateral white matter from the CC region terminate in many regions of the brain providing spinal input for sensory integration, autonomic regulation, motor and emotional responses, and limbic activation.     

In situ hybridization localization of choline acetyltransferase mRNA in adult rat brain and spinal cord

The cellular distribution of choline acetyltransferase (ChAT) mRNA within the adult rat central nervous system was evaluated using in situ hybridization. In forebrain, hybridization of a ³⁵S-labeled rat ChAT cRNA densely labeled neurons in the well-characterized basal forebrain cholinergic system including the medial septal nucleus, diagonal bands of Broca, nucleus basalis of Meynert and substantia innominata, as well as in the striatum, ventral pallidum, and olfactory tubercle. A small number of lightly labeled neurons were distributed throughout neocortex, primarily in superficial layers. No cellular labeling was detected in hippocampus. In the diencephalon, dense hybridization labeled neurons in the ventral aspect of the medial habenular nucleus whereas cells in the lateral hypothalamic area and supramammillary region were more lightly labeled. Hybridization was most dense in neurons of the motor and autonomic cranial nerve nuclei including the oculomotor, Edinger-Westphal, and trochlear nuclei of the midbrain, the abducens, superior salivatory, trigeminal, facial and accessory facial nuclei of the pons, and the hypoglossal, vagus, and solitary nuclei and nucleus ambiguus of the medulla. In addition, numerous cells in the pedunculopontine and laterodorsal tegmental nuclei, the ventral nucleus of the lateral lemniscus, the medial and lateral divisions of the parabrachial nucleus, and the medial and lateral superior olive were labeled. Occasional labeled neurons were distributed in the giantocellular, intermediate, and parvocellular reticular nuclei, and the raphe magnus nucleus. In the medulla, light to moderately densely labeled cells were scattered in the nucleus of Probst's bundle, the medial vestibular nucleus, the lateral reticular nucleus, and the raphe obscurus nucleus. In spinal cord, the cRNA densely labeled motor neurons of the ventral horn, and cells in the intermediolateral column, surrounding the central canal, and in the spinal accessory nucleus. These results are in good agreement with reports of the immunohistochemical localization of ChAT and provide further evidence that cholinergic neurons are present within neocortex but not hippocampus.     

Localization of the urotensin II receptor in the rat central nervous system

The vasoactive peptide urotensin II (UII) is primarily expressed in motoneurons of the brainstem and spinal cord. Intracerebroventricular injection of UII provokes various behavioral, cardiovascular, motor, and endocrine responses in the rat, but the distribution of the UII receptor in the central nervous system (CNS) has not yet been determined. In the present study, we have investigated the localization of UII receptor (GPR14) mRNA and UII binding sites in the rat CNS. RT-PCR analysis revealed that the highest density of GPR14 mRNA occurred in the pontine nuclei. In situ hybridization histochemistry showed that the GPR14 gene is widely expressed in the brain and spinal cord. In particular, a strong hybridization signal was observed in the olfactory system, hippocampus, olfactory and medial amygdala, hypothalamus, epithalamus, several tegmental nuclei, locus coeruleus, pontine nuclei, motor nuclei, nucleus of the solitary tract, dorsal motor nucleus of the vagus, inferior olive, cerebellum, and spinal cord. Autoradiographic labeling of brain slices with radioiodinated UII showed the presence of UII-binding sites in the lateral septum, bed nucleus of the stria terminalis, medial amygdaloid nucleus, anteroventral thalamus, anterior pretectal nucleus, pedunculopontine tegmental nucleus, pontine nuclei, geniculate nuclei, parabigeminal nucleus, dorsal endopiriform nucleus, and cerebellar cortex. Intense expression of the GPR14 gene in some hypothalamic nuclei (supraoptic, paraventricular, ventromedian, and arcuate nuclei), in limbic structures (amygdala and hippocampus), in medullary nuclei (solitary tract, dorsal motor nucleus of the vagus), and in motor control regions (cerebral and cerebellar cortex, substantia nigra, pontine nuclei) provides the anatomical substrate for the central effects of UII on behavioral, cardiovascular, neuroendocrine, and motor functions. The occurrence of GPR14 mRNA in cranial and spinal motoneurons is consistent with the reported autocrine/paracrine action of UII on motoneurons.