Neurotensin-immunoreactive Neurons Research Articles

Local inputs to aldosterone-sensitive neurons of the nucleus tractus solitarius

Aldosterone-sensitive neurons in the nucleus tractus solitarius (NTS) become activated during sodium depletion and could be key neural elements regulating sodium intake. The afferent inputs to these neurons have not yet been defined, but one source may be neurons in the area postrema, a neighboring circumventricular organ that innervates the NTS and exerts a powerful inhibitory influence on sodium appetite [Contreras RJ, Stetson PW (1981) Changes in salt intake after lesions of the area postrema and the nucleus of the solitary tract in rats. Brain Res 211:355–366]. After an anterograde axonal tracer was injected into the area postrema in rats, sections through the NTS were immunolabeled for the enzyme 11-β-hydroxysteroid dehydrogenase type 2 (HSD2), a marker for aldosterone-sensitive neurons, and examined by confocal microscopy. We found that some of the aldosterone-sensitive neurons received close appositions from processes originating in the area postrema, suggesting that input to the HSD2 neurons could be involved in the inhibition of sodium appetite by this site. Axonal varicosities originating from the area postrema also made close appositions with other neurons in the medial NTS, including the neurotensin-immunoreactive neurons in the dorsomedial NTS. Besides these projections, a dense field of neurotensinergic axon terminals overlapped the distribution of the HSD2 neurons. Neurotensin-immunoreactive axon terminals were identified in close apposition to the dendrites and cell bodies of some HSD2 neurons, as well as unlabeled neurons lying in the same zone within the medial NTS. A local microcircuit involving the area postrema, HSD2 neurons, and neurotensinergic neurons may play a major role in the regulation of sodium appetite.

Neuromodulator content of hamster intergeniculate leaflet neurons and their projection to the suprachiasmatic nucleus or visual midbrain.

The intergeniculate leaflet (IGL) of the lateral geniculate complex has widespread, bilateral, and reciprocal connections with nuclei in the subcortical visual shell. Its function is poorly understood with respect to its role in visual processing. The most well-known IGL projection, and the only one with a clear function, is the geniculohypothalamic tract (GHT) that terminates in the suprachiasmatic nucleus (SCN), site of the primary circadian clock. The hamster GHT is derived, in part, from IGL neurons containing neuropeptide Y and enkephalin. IGL neurons containing these peptides also project to the pretectal region. The present studies used a combination of immunohistochemical, lesion, and retrograde tracing techniques to study neuron types in the IGL and their projections to hamster SCN and pretectum. Two additional neuromodulators, gamma-aminobutyric acid (GABA) and neurotensin, are shown to be present in IGL neurons. The GABA- and neurotensin-immunoreactive neurons project to the SCN with terminal field patterns very similar to those for neuropeptide Y and enkephalin. IGL neurons of all four types also send projections to the pretectum, but rarely do individual cells project to both the SCN and the pretectum. Nearly all neurotensin is colocalized with neuropeptide Y in IGL neurons, although about half of the neuropeptide Y cells do not contain neurotensin. Otherwise, the extent to which the four neuromodulators are colocalized varies from 6% to 54%. Nearly every SCN neuron appears to contain GABA. In the IGL, the majority of cells studied are not identifiable by GABA immunoreactivity. Putative functions of the various neuromodulator projections from the IGL to pretectum or SCN are discussed.

Distinct and interactive effects of d-amphetamine and haloperidol on levels of neurotensin and its mRNA in subterritories in the dorsal and ventral striatum of the rat.

Striatal tissue concentrations of neurotensin, expression of neurotensin/neuromedin N (NT/N) mRNA, and numbers of neurotensin-immunoreactive neurons are increased by d-amphetamine (amph), which stimulates dopamine release in the striatum, and haloperidol (hal), a dopamine receptor antagonist with high affinity for D2-like receptors. The possibility that the effects of these drugs involve distinct subpopulations of striatal neurons was addressed in this study, in which the relative numbers and distributions of striatal neuron profiles containing neurotensin immunoreactivity and/or NT/N mRNA were compared following administrations of hal, amph, hal and amph co-administered, and vehicle. Fourteen striatal subterritories in caudate-putamen, nucleus accumbens, and olfactory tubercle were evaluated. Amph produced increases in the expression of neurotensin preferentially in the ventromedial and caudodorsal subterritories of the caudate-putamen, the rostrobasal cell cluster and lateral shell of the nucleus accumbens, and the olfactory tubercle. Haloperidol produced increased neurotensin expression in much of dorsal and ventral striatum, most prominently in the rostral, dorsomedial and ventrolateral quadrants of the caudate-putamen, and in the rostrobasal cell cluster, rostral pole, medial and lateral shell of the nucleus accumbens and the olfactory tubercle. The numbers of neurons responding to amph and hal in all subterritories following co-administration of the two drugs were significantly less than the summed numbers responding individually to amph and hal. Furthermore, in the subterritories where immunohistochemically detectable responses elicited by amph exceeded those produced by hal, co-administration of the two drugs resulted in responses comparable to those elicited by hal given alone. It is suggested that some of the reported anti-dopaminergic behavioral effects of basal ganglia neurotensin may be attenuated in conditions of reduced dopamine neurotransmission.

Apposition of enkephalin- and neurotensin-immunoreactive neurons by serotonin-immunoreactive varicosities in the rat spinal cord

The descending serotonergic system provides a powerful inhibitory input to the dorsal horn of the spinal cord. Little is known about the chemical identity of the spinal neurons that the serotonergic system innervates, although spinal enkephalinergic neurons are likely candidates. This study investigated the apposition of serotonin-immunoreactive varicosities onto enkephalin- and neurotensin-immunoreactive neurons in the rat lumbosacral spinal cord. Using a double immunofluorescence technique, serotonin-immunoreactive varicosities were observed to abut the soma or proximal dendrites of [Met]enkephalin- and neurotensin-immunoreactive neurons. Nearly 75% of all [Met]enkephalin- and neurotensin-immunoreactive neurons were apposed by serotonin-immunoreactive varicosities in the marginal zone and dorsal gray commissure. In substantia gelatinosa, approximately half of the [Met]enkephalin- and neurotensin-immunoreactive neurons were juxtaposed by serotonin-immunoreactive varicosities. [Met]enkephalin-immunoreactive neurons also were bordered by serotonin-immunoreactive varicosities in the nucleus proprius (65%) and sacral parasympathetic nucleus (75%). The results of this study suggest that the descending serotonergic system mediates nociception via probable contacts with intrinsic enkephalin and neurotensin spinal systems. The mode of action of spinal serotonin on enkephalin and neurotensin neurons may be through “volume” transmission vs synaptic or “wiring” transmission.

The catecholaminergic innervation of the rat amygdala.

The present study is the first to demonstrate conclusively and to analyze systematically synaptic contacts of all three types of catecholaminergic afferent fibers in different nuclei of the rat amygdala and to relate the catecholaminergic innervation to neurochemically identified target neurons. 4.1.1 Central Nucleus: The central nucleus is the amygdaloid nucleus receiving the most dense catecholaminergic innervation. In the medial central nucleus, dopaminergic, noradrenergic and adrenergic terminal plexus overlap, in the central lateral central nucleus mainly dopaminergic plexus are found. The lateral capsular central nucleus is generally scarcely innervated, but individual neurons of this subnucleus possess a dense dopaminergic innervation. Colocalization of neurotensin in dopaminergic afferents is rare, the majority of the dense neurotensin-ir terminal plexus consist of non-dopaminergic fibers. The catecholaminergic innervation of the medial central nucleus is directed preferentially at peripheral neuronal structures, and has thus presumably modulatory functions. Dopaminergic terminals form predominantly symmetric, noradrenergic and adrenergic terminals from preferentially asymmetric synapses. A characteristic feature of the dopaminergic innervation is the dense perisomatic innervation of selected neurons. Adrenergic and the majority of noradrenergic afferent fibers to the medial central nucleus originate from cell groups in the medulla oblongata and contain high levels of NPY. GAD mRNA-detection suggests that most target neurons of catecholaminergic afferent fibers are capable of synthesizing GABA in the medial central nucleus. In its dorsal part, GABA is possibly colocalized with somatostatin, and many neurons express the dopamine-1-receptor subtype mRNA. In the posteroventral medial central nucleus, on the other hand, enkephalin mRNA-r and dopamine-2-receptor subtype mRNA-reactive neurons show a similar distribution as the GAD mRNA-reactive ones. Contacts could be shown between dopaminergic, noradrenergic and adrenergic axons and NPY- and somatostatin-immunoreactive neurons which are supposedly among the brainstem projection neurons of the medial central nucleus. The dopaminergic innervation of the central lateral central nucleus resembles that of the neighboring striatum in many respects. The synaptic density is high. As in the medial subnucleus, distal neuronal elements are the preferential target structures, indicating a modulatory function possibly regulating the selectivity of the target neurons for stimuli transmitted by other afferent fibers. Besides, individual neurons possess a dense perisomatic, presumably non-selective dopaminergic innervation. The innervation does not appear to be targeted at one specific neurochemical type of neuron in the central lateral central nucleus, but rather contacts somatostatin- and neurotensin-immunoreactive neurons (which are possibly also GABAergic), in addition to GABA/enkephalin-synthesizing and other (e.g., CHAT-immunoreactive) neurons. Individual neurons of the central lateral central nucleus express the dopamine-2-receptor subtype mRNA. The dopaminergic fiber baskets of the lateral capsular central nucleus are found surrounding enkephalin mRNA-reactive neurons. Codistribution studies suggest that they express the dopamine-2-receptor subtype mRNA. 4.1.2 Basal Complex: The basal complex receives dopaminergic and noradrenergic innervation, the latter mainly originating in the locus coeruleus. Some of the dopaminergic afferents contain neurotensin, and in contrast to the central nucleus, all neurotensin-immunoreactive afferent fibers are dopaminergic. In the noradrenergic afferent fibers NPY is not detectable. These results and the innervation pattern displaying mostly peripheral neuronal target structures resemble dopaminergic and noradrenergic innervation patterns documented in cortical areas. (ABSTRACT TRUNCATED)

Ultrastructural study of phenylethanolamine- N-methyltransferase, corticotropin-releasing factor and neurotensin immunoreactive neurons in the external cuneate nucleus of the gerbil

The present study examined the existence of catecholamine-, corticotropin-releasing factor (CRF)- and neurotensin (NT)-containing neurons in the external cuneate nucleus (ECN) of the gerbil using single label pre-embedding immunocytochemistry in an attempt to shed light on the increasing evidence for autonomic involvement of the ECN. Peroxidase immunoreactivity of phenylethanolamine- N-methyl-transferase (PNMT), CRF or NT was identified in the heterogeneous population of the ECN neurons characterized by a deeply infolded nucleus. The label was localized in their somata, dendrites, myelinated axons and axon terminals. The immunolabelled dendrites were contacted by spherical (S) and flattened (F) types of presynaptic boutons containing spherical and flattened synaptic vesicles, respectively. The PNMT-labelled dendrites, however, were postsynaptic to an additional type of axon terminals containing pleomorphic (P) synaptic vesicles. Among the immunoreactive axon terminals, the PNMT-labelled boutons consisted of two types: S and F; in the CRF- and NT-labelled axon terminals, only the S type was observed. The catecholamine-containing ECN neurons differed from the CRF- and NT-immunoreactive neurons in their synaptic organization. The latter two were considered to be of the same cell population because of their similarities in ultrastructural features and synaptic relations. In view of a high frequency (48% for PNMT, 50% for CRF and 46% for NT) of the F-typed boutons associated with the three categories of immunolabelled neurons in the ECN, it is possible that they are under considerable inhibitory control. The presence of catecholamine, CRF and NT in the ECN suggests that the nucleus may be involved in the integration of proprioception-, exercise- or stress-evoked autonomic responses.

Neurotensin in the lateral hypothalamic area: Origin and function

The origin of neurotensin in the lateral hypothalamus was investigated by means of fluorescent retrograde tract tracing and neurotensin-like immunoreactivity. Following fluorescent retrograde tract tracing with FluoroGold combined with neurotensin immunohistochemistry in the rat brain, numerous neurotensin-immunoreactive neurons with projections to the posterior lateral hypothalamic area were identified in the central nucleus of the amygdala, perifornical area and the parabrachial nucleus. Fewer numbers of neurotensin-positive neurons with projections to the lateral hypothalamic area were observed in the bed nucleus of the stria terminalis, lateral septal nucleus, medial preoptic area, peri- and paraventricular nuclei of the hypothalamus, anterior lateral hypothalamic area and dorsal raphe nucleus. In addition, the role of neurotensin in the modulation of autonomic regulatory input from the insula was investigated. The lateral hypothalamic area was surveyed for single units responding to electrical stimulation (500-900 microA, 0.5 Hz) of sites in the insular cortex from which cardiovascular pressor or depressor responses could be elicited. These units were tested for the influence of neurotensin on responses to stimulation of the insular cortex. Of 60 spontaneously firing neurons, 27 units responded to electrical stimulation of cardiovascular sites in the insula. Of the units responding to stimulation of cardiovascular sites in the insula, 14 units showed excitation only, 10 units showed excitation followed by inhibition and three units showed inhibition. Iontophoresis of 0.1-1.0 mM neurotensin (25-100 nA, pH 5.0-6.0) potentiated six of the excitatory responses and showed no effect on the inhibitory responses. In addition, nine neurons showed an increase in spontaneous activity with iontophoresis of neurotensin. Of these neurons, three were excited by insular stimulation and six did not respond. These findings indicate the likely origin of neurotensin in the lateral hypothalamic area and demonstrate that neurotensin has a role in the modulation of some of the cardiovascular regulatory input from the insular cortex.

Distribution of neurotensin-immunoreactive neurons in the digestive tract of the chicken

The origin of the neurotensin-containing nerve fibers in the digestive tract of the chicken has been investigated with the use of colchicine and immunohistochemistry. Neurotensin-immunoreactive nerve fibers were found in the smooth muscle layers from the esophagus to the duodenum. Their density of distribution was very high in the esophagus and crop (maximum mean value: 1315/mm 2 of sectional area in the lamina muscularis mucosae of the crop) and decreased progressively to the duodenum. Neurotensin-immunoreactive neuronal cell bodies were observed after colchicine treatment in the submucosal plexuses of the esophagus and crop and in the myenteric plexuses of the esophagus, crop, proventriculus and gizzard, and they extended varicose fibers. The number of neurotensin-immunoreactive cell bodies was high in the myenteric plexus of the gizzard (28.3 ± 2.7/ganglion) but low in the plexuses of the esophagus, crop and proventriculus. Seven days after cutting the glossopharyngeal nerve and vagus nerve unilaterally, the number and extent of neurotensin-immunostained structures in the smooth muscle layers from the esophagus to the gizzard did not show any significant difference between operated and unoperated sides. These results indicate that in the chicken the great majority of neurotensin-immunoreactive enteric fibers originate in the intramural plexuses of the upper digestive wall and are mainly distributed to smooth muscle cells.

Morphology and Fos immunoreactivity reveal two subpopulations of striatal neurotensin neurons following acute 6-hydroxydopamine lesions and reserpine administration

It was previously reported that following striatal dopamine depletion or pharmacological blockade of dopamine neurotransmission, neurotensin immunoreactivity is elicited in at least two distinct subpopulations of striatal neurons (Neuroscience Vol. 46, pp. 335-350, 1992). Recently it was shown that Fos immunoreactivity, interpreted as an indicator of enhanced neuronal activity, is appreciably co-localized in only one of the subpopulations of neurotensin-immunoreactive neurons observed following blockade of the dopamine D2 receptor (Neuroscience Vol. 57, pp. 649-660, 1993). In the present study, similar methods were used to determine the degree of co-localization of Fos and neurotensin immunoreactivity in striatal neurons in response to the dopamine-depleting effects of 6-hydroxydopamine lesions and reserpine administration. It was observed that following these treatments, a subpopulation of neurons at the small end of the medium size range exhibited light neurotensin immunoreactivity and frequent co-localization with Fos immunoreactivity. This population was predominant after reserpine administration in the dorsolateral quadrant of the striatum. Another subpopulation comprised larger neurons that exhibited intense neurotensin immunoreactivity in perikarya and proximal processes that was rarely co-localized with Fos immunoreactivity. This type of neuron was observed following all the drug treatments but was present almost to the exclusion of the smaller type of cells three days following ventral midbrain 6-hydroxydopamine lesions, being mainly located in the dorsomedial and ventrolateral portions of the striatum. The present data support the results of the preceding studies in being consistent with the existence of two subpopulations of striatal neurons that accumulate neurotensin following dopamine depletion. The possibility is considered that one subpopulation accumulates neurotensin in response to co-ordinate increases in neuronal activity and neurotensin synthesis, and the other as a result of decreased release.

Phylogenetic aspects of the occurrence and distribution of secretogranin II immunoreactivity in lower vertebrate gut.

A novel monoclonal antibody raised against bovine secretogranin II (Sg II) was used in immunohistochemical studies on amphibian (Rana esculenta), reptilian (Podarcis sicula) and avian (Gallus gallus) gut. Sg II immunoreactivity was detected in epithelial and nervous elements. Cells immunoreactive for Sg II were examined by double immunostainings to determine whether they might also co-store certain previously known bioactive amine/peptide substances. Almost all the endocrine cells immunoreactive for bombesin, substance P, neurotensin, gastrin/cholecystokinin, neuropeptide tyrosine (NPY) and calcitonin gene-related peptide as well as some of those immunostained for serotonin, histamine, and polypeptide tyrosine tyrosine (PYY) also contained Sg II. Sg II-immunoreactive cells varied in number and distribution according to regions of the gut and animal species. The number of Sg II immunoreactive granules notably varied not only according to cell type, but also within the same cell population. Many histamine-, calcitonin gene-related peptide (CGRP)-, substance P-, PYY-, and neurotensin-immunoreactive neurons also contained Sg II. These were mostly situated in the myenteric plexus; their distribution pattern varied among the three species. These findings show that, despite being well conserved during phylogeny, Sg II has a heterogeneous distribution.

Subsets of neurotensin-immunoreactive neurons in the rat striatal complex following antagonism of the dopamine D 2 receptor: An immunohistochemical double-labeling study using antibodies against Fos

A study was done to determine if the Fos and neurotensin immunoreactivities elicited in the rat striatal complex by the selective dopamine D 2 receptor antagonist, S(−)-eticlopride hydrochloride are co-localized in the same neurons. Following injections of eticlopride, Fos and neurotensin immunoreactivity were both non-uniformly distributed among the striatal compartments and subterritories. Fos was co-localized in a significant number of small, lightly neurotensin-immunoreactive neurons, but not in a larger subset of neurons with significantly greater median diameter that exhibited intense neurotensin immunoreactivity extending well into the dendritic arbor. It is proposed that neurotensin-immunoreactive neurons lacking Fos immunoreactivity are prominent following selective blockade of the dopamine D 2 receptor and represent a subset of striatal neurotensin-immunoreactive neurons. Neurotensin-immunoreactive cells containing Fos nuclei represent a distinct subset, possibly the one that is dominant following administration of reserpine [Zahm (1992) Neuroscience 46, 335–350]. Insofar as Fos expression has been reported to accompany activation of striatonigral and striatopallidal neurons, the absence of Fos in the subset of neurotensin neurons displayed following D 2 receptor blockade may be at odds with activation and perhaps is more consistent with inactivation and accompanying decreased release of neurotensin [see Frey et al. (1988) Neurochem. Int. 12, 33–38, and Bean et al. (1989) J. Neurosci. 9, 4430–4438] as a mechanism underlying the accumulation of neurotensin in that subset of striatal neurons.

Immunocytochemical evidence that GABA and neurotensin exist in different neurons in laminae II and III of rat spinal dorsal horn

Pre-embedding immunocytochemistry with antiserum to neurotensin was combined with post-embedding immunocytochemistry with GABA antiserum, in order to identify neurotensin- and GABA-containing neurons in laminae I-III of rat spinal dorsal horn. The distribution of cell bodies containing these two compounds was similar to that which has been described previously. None of the 88 neurotensin-immunoreactive neurons which were tested showed GABA-like immunoreactivity, which suggests that GABA and neurotensin exist in different cells in this region. Since both compounds are thought to be present in islet cells, it is likely that there are two neurochemically distinct populations of islet cells in lamina II of rat spinal cord.

Subsets of neurotensin-immunoreactive neurons revealed following antagonism of the dopamine-mediated suppression of neurotensin immunoreactivity in the rat striatum

The distribution of neurotensin-immunoreactive structures in the rat striatum was evaluated after blockade of dopamine neurotransmission by drugs that act presynaptically (6-hydroxydopamine, reserpine) and postsynaptically, preferentially at the D 2 (eticlopride, haloperidol) and D 1 [( R)-(+)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazepin-7-ol, SCH-23390] receptor sites. Calbindin-D (mol. wt 28,000) immunoreactivity was used to delineate patch (striosome) and matrix in the caudate-putamen and core and shell in the nucleus accumbens. Antagonism at the D 2 dopamine receptor and 6-hydroxydopamine lesions caused dense axonal immunoreactivity and moderate numbers of neurotensin-immunoreactive neurons to be distributed preferentially in the matrix of the caudate-putamen. D 1 receptor antagonism was significantly less effective at eliciting neurotensin-immuno-reactive neurons in the caudate-putamen. Reserpine or co-administration of the D 1 and D 2 receptor antagonists produced many neurotensin-immunoreactive neurons in both striatal compartments throughout the caudate-putamen and dense axonal neurotensin immunoreactivity in the medial patch compartment. To varying degrees, with SCH-23390 being least effective and reserpine most effective, all of the drug treatments elicited neurotensin immunoreactivity in neurons in the olfactory tubercle, rostral nucleus accumbens, accumbal shell and ventrolateral caudate-putamen, i.e. most of the ventral striatum.

Neurotensin‐lmmunoreactive Neurons in the Rat Medial Preoptic Area are Oestrogen‐Receptive

The identity of neurons influenced by oestrogen is critical for the understanding of ovarian steroid actions in the brain. The medial preoptic area (MPOA) contains one of the largest oestrogen-receptive cell populations in the rat brain and participates in several oestrogen-dependent functions, including the regulation of luteinizing hormone (LH) secretion and sexual behaviour. Using double immunostaining procedures with antibodies specific for the oestrogen receptor and neurotensin, a neuropeptide implicated in the regulation of LH secretion within this area, we found that approximately half of the neurotensin-immunoreactive neurons in the MPOA also displayed immunoreactivity for the oestrogen receptor. We estimate that oestrogen-receptive neurotensin neurons represent 5% to 12% of all oestrogen receptor-positive cells in the MPOA. Our results provide morphological evidence that neurotensin mediates oestrogen-dependent mechanisms within the brain and suggest that oestrogen may act through preoptic neurotensin neurons to aid in the generation of the LH surge.

The striatal mosaic in primates: Patterns of neuropeptide immunoreactivity differentiate the ventral striatum from the dorsal striatum

Patterns of immunoreactivity for calcium-binding protein, tyrosine hydroxylase and four neuropeptides in the ventral striatum (nucleus accumbens, olfactory tubercle and ventromedial parts of the caudate nucleus and putamen) were compared to patterns of these markers in the dorsal striatum (the majority of the neostriatum) in rhesus monkey. The striatal mosaic was delineated by calcium-binding protein and tyrosine hydroxylase immunoreactivities. Both markers were found preferentially in the matrix of the dorsal striatum. The mosaic configurations of tyrosine hydroxylase, but not calcium-binding protein immunoreactivity, were similar in dorsal and ventral striatal regions. Substance P and leucine-enkephalin were not distributed homogeneously; distinct types and the prevalence of patches of substance P and leucine-enkephalin immunoreactivity distinguish the dorsal striatum from the ventral striatum and distinguish the caudate nucleus from the putamen. In the dorsal striatum, substance P and leucine-enkephalin patches consist of dense islands of immunoreactive neurons and puncta or clusters of immunoreactive neurons marginated by a dense rim of terminal-like puncta; the matrix was also enriched in leucine-enkephalin-immunoreactive neurons but contained less substance P-immunoreactive neurons. Patches were more prominent in the caudate nucleus than in the putamen. In the caudate, compartments low in tyrosine hydroxylase and calcium-binding protein immunoreactivities corresponded to cytologically identified cell islands and to patches enriched in substance P and leucine-enkephalin. These patches had a discrete infrastructure based on the location of substance P and leucine-enkephalin-immunoreactive neurons and terminals. In the ventral striatum, patches that showed low levels of substance P and leucine-enkephalin immunoreactivities were embedded in a matrix rich in immunoreactive cell bodies, fibers and terminals. In the accumbens, regions showing little tyrosine hydroxylase were in spatial register with patches low in substance P and leucine-enkephalin. Neurotensin- and somatostatin-immunoreactive neurons or processes were also compartmentally organized, particularly in the ventral striatum. Neurotensin-immunoreactive neurons were present predominantly in the nucleus accumbens but not in the dorsal striatum. Some regions enriched in neurotensin immunoreactivity were spatially registered with zones low in tyrosine hydroxylase, substance P and zones enriched in leucine-enkephalin. Areas enriched in somatostatin-immunoreactive processes overlapped with both tyrosine hydroxylase-rich and -poor regions in the ventral striatum. Our results show that the chemoarchitectonic topography of the striatal mosaic is different in the dorsal and ventral striatum of rhesus monkey and that the compartmental organization of some neurotransmitters/neuropeptides in the ventral striatum is variable and not as easily divisible into conventional patch and matrix regions as in the dorsal striatum. These various markers may be revealing more than one pair of compartmental boundaries within the striatum.

Organization of peptidergic and catecholaminergic efferents from the nucleus of the solitary tract to the rat amygdala

Previous studies have focused on the role of the central nucleus of the amygdala (CeA) in cardiovascular and other amygdaloid functions. The combined retrograde tracing/immuno-histochemical method was used to test for the presence of enkephalin, neurotensin, neuropeptide Y, and catecholamine neurons within the nucleus of the solitary tract that send efferents to the CeA. After injections of retrograde tracer into the CeA, retrogradely labeled neurons were observed within the caudal, medial nucleus of the solitary tract. Most CeA-projecting neurons were located ipsilaterally within the medial nucleus of the solitary tract at the level of the area postrema. Retrogradely labeled enkephalin- and neurotensin-immunoreactive neurons were found within the medial nucleus of the solitary tract at this level, while retrogradely labeled neuropeptide Y-immunoreactive neurons were found within the medial nucleus of the solitary tract rostral to the area postrema. About 60–74% of CeA-projecting cells were also immunoreactive for tyrosine hydroxylase. Approximately 9% of retrogradely neurons were phenylethanolamine-N-methyltransferase immunoreactive. The results provide evidence that within the nucleus of the solitary tract, peptidergic CeA-projecting neurons have a topographic distribution. In addition, noradrenergic neurons within the A2 group, rather than adrenergic neurons of the C2 group, provide the bulk of catecholaminergic input to the CeA from the nucleus of the solitary tract. Cell counts indicate that each of these peptides may be colocalized (to varying extents) within catecholamine-producing neurons. Also the Catecholaminergic and enkephalinergic contribution to the ascending pathway from the nucleus of the solitary tract to the CeA distinguishes it neurochemically from the descending pathway. Thus, although there are afferent and efferent connections between the nucleus of the solitary tract and CeA, their peptidergic/neurotransmitter connections are not necessarily reciprocal. Input from nucleus of the solitary tract peptidergic and catecholaminergic neurons to the CeA may be important in the etiology of a number of pathophysiological conditions including hypertension, gastric ulcers, and schizophrenia.

Comparison of met‐enkephalin, dynorphin a, and neurotensin immunoreactive neurons in the cat and rat spinal cords: II. Segmental differences in the marginal zone

This study examined the number of met-enkephalin, dynorphin A 1-8, and neurotensin immunoreactive (IR) neurons in the marginal zone (lamina I) at one thoracic (T8:cat,T9:rat), one midlumbar (L5:cat,L4:rat), and one lower lumbar or sacral (S1:cat,L6:rat) spinal cord segment in the cat and rat. Marginal zone IR neurons ranged 10-70 microns in diameter in cats and 10-50 microns in rats and were flattened, pyramidal, fusiform, or polygonal in morphology. Immunoreactive neurons for each peptide in both species were found in the marginal zone at all spinal levels, but with a differential segmental distribution. The average number of IR neurons per 50-microns section generally was lowest in thoracic cord and greatest in lower lumbar/sacral cord for all peptides. For enkephalin and dynorphin, the estimated total number of IR neurons per segment and number of IR neurons per volume (mm3) generally were lowest in the midlumbar segments and highest in the thoracic and lower lumbar/sacral cord. For neurotensin, the estimated total number of neurons per segment remained lowest in the thoracic and largest in the lower lumbar/sacral cord. The number of neurotensin IR neurons per volume was equal in the thoracic and midlumbar cord, but remained highest at lower lumbar/sacral levels. The IR neurons quantified in this study may be interneurons or may serve as supraspinal projection neurons. The large number of IR neurons observed in segments receiving a relatively large visceral afferent input suggests that some of these neurons may be involved in visceral sensory processing. In addition, the segmental distribution of the IR neurons indicates that physiological and pharmacological studies on the effects of opioid and/or neurotensin peptides should be interpreted in light of the spinal segment(s) investigated.

Canine enteric submucosal cultures: Transmitter release from neurotensin-immunoreactive neurons

A culture system of dispersed submucosal neurons from canine ileum has been developed. The neuronal nature of over 80% of the cells in culture was confirmed by positive staining with a neurofilament antibody. In this culture system, neurotensin-immunoreactive neurons constituted greater than 50% of the total cell population. Neurotensin immunoreactivity in these cells was chromatographically characterized as a single molecular form coeluting with synthetic neurotensin (1–13). We have assessed the release of immunoreactive neurotensin by stimulatory and inhibitory transmitters, and by post-receptor activators of cell function. Forskolin (10 μM), the calcium ionophore A23187 (100 nM), and the active phorbol ester β-12 myristrate 13-acetate (10 nM), each significantly increased neurotensin release compared with basal peptide secretion. The concomitant application of ionophore and phorbol ester resulted in a marked increase in neurotensin release and this stimulatory response was inhibited over 70% by somatostatin (100 nM). Substance P (0.1–100 nM) caused a dose-dependent increase in neurotensin release. Somatostatin (100 nM) reduced maximal stimulation with 100 nM substance P by 79%. Our results suggest that this submucosal culture system represents an entirely new model for characterizing transmitter release from enteric neurons.

Ventral striatopallidal parts of the basal ganglia in the rat: I. Neurochemical compartmentation as reflected by the distributions of neurotensin and substance P immunoreactivity

The distribution of neurotensin immunoreactivity in the basal ganglia of the adult rat was evaluated by studying alternate serial vibratome sections that were exposed to antiserum against neurotensin, substance P, or cholecystokinin. It was observed that a heterogeneous distribution of neurotensin-immunoreactive fibers and terminals contributes to the neurochemical compartmentation of the ventral pallidum and ventral striatum, and that significant numbers of neurotensin-immunoreactive neurons occupy striatal districts of the olfactory tubercle, nucleus accumbens, and ventromedial caudate-putamen. An intense band of pallidal neurotensin immunoreactivity characterizes the medial part of the ventral pallidum adjacent to the nucleus accumbens, whose medial boundary is conveniently defined in sections incubated with cholecystokinin antiserum. Electron microscopic studies showed that the pallidal plexus of neurotensin-immunoreactive elements consists primarily of boutons, which contact large dendrites in arrangements that in all respects appear to be of the classical striatopallidal variety. A gradual decrease in immunolabel was observed approaching the lateral parts of the ventral pallidum, which display sparse neurotensin immunoreactivity. The results thus indicate the existence of a significant neurotensinergic striatopallidal pathway confined primarily, if not exclusively, to the medial part of the ventral striatopallidal system. The contribution of neurotensin-immunoreactive fibers and terminals to the compartmentation of ventral striatum is expressed most vividly in their exclusion from clusters of tightly packed medium-sized neurons, many of which are intensely substance P immunoreactive. Such clusters appear identical with those previously described as rich in opiate receptors and poor in acetylcholinesterase activity. In the ventral striatal region where the nucleus accumbens and ventromedial caudate-putamen merge, neurotensin-immunoreactive neurons are organized in clusters. Further rostral in the nucleus accumbens, they are more evenly distributed. Few were found in the dorsolateral quadrant of the neostriatum.

Distribution pattern of cell bodies and fibers with neurotensin-like immunoreactivity in the cat hypothalamus.

Neurotensin is widely distributed in the central and peripheral nervous systems. Extensive radioimmunoassay and immunohistochemical studies in rats show that the neurotensin immunoreactive perikarya and fibers are most prominent in the hypothalamus. Radioimmunoassay studies have suggested that the levels of neurotensin in the hypothalamus of cats may be six times higher than that of rats. We studied the distribution pattern of neurotensin immunoreactivity within the hypothalamus of the cat by avidin-biotin modification immunohistochemical methods: (1) to define its distribution pattern within the hypothalamus, and (2) to compare our findings with the patterns that have been described in rats. Results show that neurotensin immunoreactive cell bodies and fibers are most prominent in the rostral and intermediate regions of the cat hypothalamus. Cell bodies with neurotensin-like immunoreactivity are seen maximally in the medial preoptic region, the infundibular nucleus, and the lateral hypothalamus. The neurotensin positive fibers are dense in the periventricular regions of the entire rostro-caudal extent of the hypothalamus. This pattern of distribution of neurotensin immunoreactivity is similar to that described in rats. The suprachiasmatic nuclei of the cat hypothalamus, however, contained a significant number of neurotensin immunoreactive cell bodies, an observation not noted in the rat hypothalamus. The neurotensin immunoreactive neurons were more numerous in the lateral hypothalamus than has been reported in rats, but the paraventricular nucleus of the hypothalamus in cats contained fewer neurotensin immunoreactive perikarya. The presence of neurotensin immunoreactive perikarya in the suprachiasmatic nucleus and the apparent increase in the number of neurotensin immunoreactive neurons in the lateral hypothalamus may account for the increased levels of neurotensin reported in cats. Neurotensin has been speculated to play a role in nociception, thermoregulation, and control of arterial pressure by acting as a hormone or a neurotransmitter. Details of the pattern of colocalization of neurotensin with that of other neuropeptides and neurotransmitters will aid in our understanding of its role in these functions.