Biomedical subjects

A Beaudet

Publications and source records attributed to A Beaudet.

At least 127 records · Page 7Linked to original sources

PubMed1989

Association of neurotensin binding sites with sensory and visceromotor components of the vagus nerve.

Specific neurotensin (NT) binding sites were recently shown to be highly concentrated in the nucleus of the solitary tract (NTS), which receives primary vagal afferents, and in the dorsal motor nucleus of the vagus (DMN), which contains the cell bodies of origin of vagal preganglionic neurons. To investigate the relationship of these binding sites with sensory and visceromotor components of the vagus nerve, they were labeled here in vitro, using monoiodo[Tyr3]neurotensin (125I-NT) and visualized by light microscopic radioautography in the dorsomedial medulla of both intact and unilaterally vagotomized rats, in the nodose ganglia of intact animals, and in ligated vagus nerves. Unilateral vagotomy performed above the nodose ganglion resulted in a significant ipsilateral decrease in 125I-NT binding within both the NTS and the DMN, suggesting that NT binding sites were associated with both primary afferent fibers and preganglionic nerve cell bodies. The selective radioautographic labeling of a subpopulation (approximately 15%) of neuronal perikarya in the nodose ganglion confirmed that a proportion of vagal afferent neurons contained NT binding sites. Following vagus nerve ligation, a pile up of radiolabeled NT binding sites was observed on both sides of the nerve crush, indicating that NT receptor components were transported both anterogradely and retrogradely along fibers of the vagus nerve. We conclude that NT receptors are synthesized and transported within a subpopulation of afferent and efferent components of the vagus nerve and that NT may therefore act presynaptically upon vagal axon terminals in both central and peripheral nervous systems.

Animals↗

PubMed1988

Light and electron microscopic study of tyrosine hydroxylase-immunoreactive neurons within the developing rat arcuate nucleus.

The topography, fine structure, and patterns of connections of tyrosine hydroxylase (TH)-immunoreactive tubero-infundibular dopaminergic (TIDA) neurons were examined by light and electron microscopic immunocytochemistry in the arcuate nucleus of 2-, 15- and 30-day-old female Wistar rats. In 2-day-old animals, TH-immunoreactive perikarya were mainly located in the ventrolateral portion of the arcuate nucleus. In 15-day-old rats numerous TH-positive cell bodies were still present ventrolaterally, but a cluster of labeled cells was also apparent in the mediodorsal segment of the nucleus. In the 30-day-old rats, most TH-immunoreactive neurons were concentrated mediodorsally, as seen in the adult. At the ultrastructural level, TH-immunoreactive somata exhibited, in all age groups, a large nucleus surrounded by a thin rim of cytoplasm containing mitochondria, Golgi apparatus, endoplasmic reticulum, multivesicular bodies and lysosomes. These labeled somata were synaptically contacted by unlabeled axon terminals and often laid adjacent to either labeled or unlabeled dendrites. Similarly, in all age groups, labeled dendrites were synaptically contacted by unlabeled axon terminals and were often directly apposed to either labeled or unlabeled perikarya and dendrites, or to tanycytic processes. These results indicate that TIDA neurons establish extensive connections early in development, and that their pattern of intercellular relationships remains qualitatively unchanged from 2 days to adulthood. It is suggested that TIDA neurons may be already functional at birth, and could therefore, influence the maturation of other arcuate neuronal populations.

Aging↗

PubMed1988

Reinnervation of dopamine neurons by regenerating serotonin axons in the rat medial zona incerta. A combined radioautographic and immunocytochemical ultrastructural study.

Cellular relationships between serotonin (5-HT) axons and tyrosine hydroxylase (TH)-containing neurons were examined by combined (3H)5-HT uptake radioautography and TH immunocytochemistry in the medial zona incerta (ZI) of adult rats, 7 and 50 days after an intracerebral injection of 5,7-Dihydroxytryptamine (5,7-DHT). Seven days post-lesion, only rare, scattered (3H)5-HT-labeled axon terminals were apparent in the zone of the medial ZI accessible to intraventricularly injected (3H)5-HT. In contrast, in sham-injected animals (3H)5-HT-labeled varicosities were numerous and often observed adjacent to TH-immunoreactive perikarya and dendrites. Fifty days post 5,7-DHT injection, the density of (3H)5-HT-labeled terminals approximated that seen in sham-treated animals. At the ultrastructural level, these regenerated 5-HT axons were similar in size, shape and content to those observed in sham-operated rats. Also, as in sham, some of the (3H)5-HT-labeled axons were directly apposed to TH-immunopositive labeled profiles. The latter included large dendritic shafts and dendritic spines, but only rare perikarya. In both sham- and 5,7-DHT-treated animals a few of the contacts between (3H)5-HT-labeled and TH-immunoreactive profiles exhibited an asymmetric synaptic differentiation. These results indicate that 5-HT fibers in the medial ZI, following regeneration, can reestablish normal relationships and even synapses with a given population of chemically identified cells.

5,7-Dihydroxytryptamine↗

PubMed1988

Phenylalanine hydroxylase expression in liver of a fetus with phenylketonuria.

The expression and activity of phenylalanine hydroxylase was studied in the liver of a fetus aborted after prenatal diagnosis of phenylketonuria. No phenylalanine hydroxylase enzymatic activity or immunoreactive protein was detectable in the PKU liver specimen, though both enzymatic activity and immunoreactive protein were detectable in control specimens of similar gestational age. Phenylalanine hydroxylase messenger RNA of normal size was present in the PKU fetal liver at normal abundance. These results confirm the genetic diagnosis of PKU in this fetus and indicate that the mutations in this fetus affect translation or stability of the phenylalanine hydroxylase protein.

Abortion, Induced↗

PubMed1988

Effects of ovariectomy and estradiol replacement on the binding of 125I-neurotensin in rat suprachiasmatic nucleus.

Distribution and density of specific high-affinity 125I-neurotensin-binding sites were examined by light microscopic radioautography in the suprachiasmatic nucleus (SCN) of normal cycling, ovariectomized, or ovariectomized and estradiol-implanted female rats. In all three experimental groups, intense 125I-neurotensin labeling was detected within the ventrolateral component of the SCN. Whereas the topographic distribution and spread of the label was similar between each group, the density of the label was significantly higher (mean increase: 122%) in ovariectomized than in normally cycling females within the rostral third of the SCN. This effect was no longer apparent in females chronically implanted with estradiol at the time of gonadectomy. These results indicate that plasma gonadal steroids may regulate neurotensin receptors in the rat SCN. It is suggested that this mechanism might be implicated in the feedback control of gonadotropin and prolactin secretion.

Animals↗

PubMed1988

Photoaffinity labeling of opioid delta receptors with an iodinated azido-ligand: [125I][D-Thr2,pN3Phe4,Leu5]enkephalyl-Thr6.

The photoaffinity ligand of the delta opioid receptor Tyr-D-Thr-Gly-pN3Phe-Leu-Thr (azido-DTLET) was iodinated and purified by high performance liquid chromatography. Monoiodo-azido-DTLET displayed a high affinity (KD = 15 nM) and is selective (Kl mu/Kl delta = 9.8) for rat brain delta opioid receptors (for comparison, the corresponding values for tritiated azido-DTLET are KD = 1.66 nM and Kl mu/Kl delta = 27). On rat brain sections, the anatomical distribution of [125I]azido-DTLET binding sites revealed by autoradiography corresponds to that of delta receptors. On rat brain membrane homogenates and NG108-15 hybrid cells, UV irradiation of the receptor-ligand complex results in the irreversible binding to membrane proteins of 14% of the bound radioactivity Gel electrophoresis of [125I]azido-DTLET-labeled proteins followed by autoradiography shows a different pattern in rat brain and NG108-15 cells. In rat brain, labeling of two of these proteins, with molecular weights of 44,000 and 34,000, was inhibited by 30 nmol/liter of nonradioactive DTLET, a delta-selective ligand but not by the same concentration of [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin, a mu-selective ligand. In NG108-15 cells, this 44-kDa protein was not visualized; the main band was at 33 kDa and disappeared in the presence of levorphanol.

Affinity Labels↗

PubMed1988

Recombinations between IRP and cystic fibrosis.

A candidate gene for cystic fibrosis was recently isolated by selective cloning of HpaII-tiny-fragment islands; it maps considerably closer to CF than does MET or D7S8 (pJ3.11), and DNA polymorphisms from this region are in marked disequilibrium with CF. cDNA cloning has shown that this protein has a growth factor-like structure and shows homology to the murine and human proto-oncogene int-1; it is designated IRP (int-1-related protein). DNA sequences from the IRP locus that recognize RFLPs are proving to be highly informative for prenatal diagnosis. We report five crossovers that have been identified which occur either within the IRP locus or between IRP and CF; these recombinants demonstrate that CF maps between the DNA markers D7S8 and KM.19.

Cystic Fibrosis↗

PubMed1987

Selective association of neurotensin receptors with cholinergic neurons in the rat basal forebrain.

Neurotensin (NT) is a putative neurotransmitter, the central and peripheral actions of which appear to be mediated by specific high affinity receptors. Recent autoradiographic studies have localized a high proportion of these NT receptors over nerve cell bodies in rat basal forebrain. In the present study, monoiodo-NT-labeled binding sites are shown by combined autoradiography and cholinesterase histochemistry to be selectively associated with cholinergic nerve cell bodies in the diagonal band and substantia innominata of the rat basal forebrain. This finding suggests that endogenous NT may directly influence forebrain cholinergic function in the central nervous system.

Acetylcholinesterase↗

PubMed1987

Serotonin axon terminals in the ventral tegmental area of the rat: fine structure and synaptic input to dopaminergic neurons.

The serotoninergic (5-hydroxytryptamine, 5-HT) innervation of the rat ventral tegmental area (VTA) was examined by light and electron microscopic radioautography following intraventricular infusion of [3H]5-HT. The [3H]5-HT labeled processes were characterized with respect to their regional distribution, ultrastructure and relationships with all neurons, including dopaminergic neurons, identified in the same sections using immunocytochemistry for the localization of the catecholamine-synthesizing enzyme, tyrosine hydroxylase (TH). By light microscopy, [3H]5-HT labeled axons and axonal varicosities were detected throughout the interfascicular nucleus and ventral portion of the VTA. By electron microscopy, [3H]5-HT-labeled axons were found to be mainly small and unmyelinated, although a few showed several lamellae of myelin. The labeled varicosities measured 0.6 micron in mean diameter and contained many small, round or flattened agranular vesicles and a few large granular vesicles. More than 18% showed synaptic specializations in single thin sections. Most of these synapses were asymmetric and established on dendritic shafts. Based on the probability of seeing such synaptic specializations in single thin sections, it was estimated that as many as 50% of the labeled 5-HT terminals formed synaptic contacts in the VTA. In dually labeled light microscopic sections, [3H]5-HT-accumulating processes often appeared adjacent to TH-immunoreactive perikarya and proximal dendrites. Electron microscopy demonstrated that terminals with radioautographic labeling for 5-HT formed conventional synapses both with TH-labeled and unlabeled dendrites in the VTA. Many additional 5-HT terminals lacking recognizable synaptic densities were directly apposed to TH-labeled dendrites and were isolated from the rest of the neuropil by thin glial leaflets. These results suggest that 5-HT neurons innervate both dopaminergic and non-dopaminergic neurons in the VTA and may influence mesocortical and mesolimbic efferent systems through synaptic as well as non-synaptic mechanisms.

Animals↗

PubMed1987

Temporal effects of intrahypothalamic 5,7-dihydroxytryptamine: relationship between serotonin levels and [3H]serotonin binding.

The relationship between serotonin (5-HT) levels and [3H]5-HT binding in discrete hypothalamic areas was examined in separate groups of animals at various times, following unilateral intrahypothalamic injection of 5,7-dihydroxytryptamine (5,7-DHT). Seven days post-5,7-DHT lesion, 5-HT levels were significantly decreased in both the ipsilateral and contralateral ventromedial and dorsomedial hypothalamic nuclei (VMN, DMN). In the lateral hypothalamic area (LHA), 5-HT levels were significantly decreased only ipsilaterally. Fifty days postlesion, 5-HT levels in the ipsilateral VMN remained significantly below sham, while the DMN and LHA returned to sham values. Seven days after 5,7-DHT there was a significant increase in [3H]5-HT labeling densities in the ipsilateral and contralateral ventromedial hypothalamic area as well as in the ipsilateral LHA. In contrast, in the dorsomedial hypothalamic area there was no increase in [3H]5-HT binding. Fifty days postlesion, no significant differences in [3H]5-HT binding between 5,7-DHT and sham were observed in any areas examined. This data provides further evidence for the regeneration of 5-HT fibers in the hypothalamus and demonstrates that the relationship between [3H]5-HT binding and 5-HT levels varies from one hypothalamic area to another.

5,7-Dihydroxytryptamine↗

PubMed1987

Distribution of acetylcholine and catecholamine neurons in the cat brainstem: a choline acetyltransferase and tyrosine hydroxylase immunohistochemical study.

The distribution of acetylcholine neurons in the brainstem of the cat was studied by choline acetyltransferase (ChAT) immunohistochemistry and compared to that of catecholamine neurons examined in the same or adjacent sections by tyrosine hydroxylase (TH) immunohistochemistry. The largest group of ChAT-positive (+) neurons was located in the lateral pontomesencephalic tegmentum within the pedunculopontine tegmental nucleus and the laterodorsal tegmental nucleus rostrally and within the parabrachial nuclei and locus coeruleus nucleus more caudally. TH+ neurons were found to be coextensive and intermingled with ChAT+ neurons in the dorsolateral pontomesencephalic tegmentum, where the number of ChAT+ cells (approximately 18,500) exceeded that of the TH+ cells (approximately 12,000). In the caudal pons, scattered ChAT+ neurons were situated in the ventrolateral tegmentum together with TH+ neurons. In the medulla, numerous ChAT+ cells were located in the lateral tegmental field, where they extended in a radial column from the dorsal motor nucleus of the vagus to the ventrolateral tegmentum around the facial and ambiguus nuclei, occupying the position of preganglionic parasympathetic neurons of the 7th, 9th, and 10th cranial nerves. TH+ cells were also present in this field. Neurons within the general visceral, special visceral, and somatic motor cranial nerve nuclei were all immunoreactive to ChAT. Scattered ChAT+ neurons were also present within the medullary gigantocellular and magnocellular tegmental fields together with a small number of TH+ neurons. Other groups of ChAT+ cells were identified within the periolivary nuclei, parabigeminal nucleus, prepositus hypoglossi nucleus, and the medial and inferior vestibular nuclei. Acetylcholine neurons thus constitute a heterogeneous population of cells in the brainstem, which in addition to including the somatic and visceral efferent systems, comprises many other discrete systems and represents an important component of the brainstem reticular formation. The proximity to and interdigitation with catecholamine neurons within these systems may be of important functional significance.

Acetylcholine↗

PubMed1987

Opioid receptors in rat neostriatum: radioautographic distribution at the electron microscopic level.

The distribution of mu-opioid receptors, selectively labeled in vitro with a monoiodinated Met-enkephalin analog [( 125I]FK 33-824), was analyzed by light and electron microscopic radioautography in sections from the neostriatum of the rat. In the light microscope, patches of high receptor densities were detected amidst a moderately labeled matrix. The number of silver grains, as counted in 1-micron thick plastic-embedded sections, was 3 times greater inside the patches than in the intervening matrix. In both compartments, the proportion of labeled binding sites associated with the neuropil was significantly higher (greater than 70%) than that associated with nerve cell bodies or myelinated fascicles. Quantitative analyses of electron microscopic radioautographs revealed that the majority of silver grains corresponding to specifically bound [125I]FK molecules originated from radioactive sources associated with apposed neuronal membranes. Of the total number of specific binding sites, 53% was associated with axodendritic, 18% with axoaxonic and 3% with axosomatic interfaces. The occurrence of multiple labeled foci along the plasma membrane of certain perikarya and dendrites suggested that some of the binding sites might be associated with somato/dendritic elements. The high incidence of labeling along axoaxonic interfaces indicated that others were linked to the membrane of axons and/or axon terminals. A major finding of the present study was that only a small proportion of specific FK binding sites (7% of total) was associated with synaptic junctions. Labeled synapses were primarily of the asymmetric type and were found predominantly on dendritic branches and spines. A few were observed on nerve cell bodies. Labeled symmetric synapses were rare and encountered exclusively on dendritic branches. The high frequency with which specifically labeled binding sites were found to be associated with neuronal interfaces involving axonal processes strongly suggests that even if non-junctional these binding sites correspond to functional receptors. Whether these receptors are activated by endogenous ligand molecules released by the labeled terminals themselves or from terminals located at a distance from the labeled interfaces remains to be determined.

Animals↗

PubMed1987

Ultrastructural distribution of alpha-bungarotoxin binding sites in the suprachiasmatic nucleus of the rat hypothalamus.

The distribution of (125I) alpha bungarotoxin (alpha-BTX) binding sites in the suprachiasmatic nucleus (SCN) of the adult female rat was examined by electron-microscopic autoradiography. The ultrastructural distribution of silver grains was analysed by line source, direct point count, and 50% probability circle methods. Real grain distribution was significantly different from that of randomly generated hypothetical grains. Line source analysis demonstrated two populations of sources: one associated with membranes, and one inside neuronal structures. Probability circle analysis of shared grains indicated that membrane-bound-radioactive sources were mainly associated with axo-dendritic appositions. Only a small proportion of labeled neuronal interfaces exhibited synaptic differentiations in the plane of section. However, the compartment containing synaptic terminals was the most enriched when comparing real to hypothetical grains. Probability circle analysis of exclusive grains demonstrated that sources that were not associated with neuronal plasma membranes were likely to be within nerve cell bodies and dendrites. It is concluded that the majority of specifically labelled alpha-BTX binding sites in the SCN is membrane bound, and may be associated with axodendritic synaptic transmission. The presence of a significant proportion of the label in the soma and dendrites of suprachiasmatic neurons 24 h after ventricular infusion suggests that some of the labeled binding sites (junctional or nonjunctional) may be internalized within these two compartments.

Animals↗

PubMed1987

Electron-microscopic characterization of adrenergic axon terminals in the diencephalon of the rat.

The fine structure of adrenergic axon terminals was examined in the paraventricular nucleus of the thalamus (PNT) and in the hypothalamic arcuate nucleus-median eminence (ARC-ME) complex by use of phenylethanolamine-N-methyl transferase (PNMT) immunocytochemistry. In the PNT, immunoreactive terminals formed a dense and well-circumscribed plexus. In the ARC, labeled varicosities were less numerous and more evenly distributed. In the ME, they were scarce and confined to the inner zone. In all these areas, the diameter of immunoreactive varicosities ranged between 0.2 and 1.3 micron; in the ME and in the transitional zone between the ARC and the ME, a population of larger boutons (greater than 2 microns) was also visible. All immunoreactive varicosities exhibited densely packed small, clear vesicles associated with a few large granular vesicles. In the PNT and the ARC, but not in the ME, they formed synaptic contacts with dendritic elements and were occasionally apposed to neuronal cell bodies. These axo-somatic appositions showed no junctional specializations. In the ME and transitional zone, immunoreactive terminals were frequently juxtaposed to, and occasionally established differentiated synaptic contacts with, tanycytes. These data support a transmitter role for adrenaline in the diencephalon and suggest that adrenaline plays a role in hypothalamo-hypophysiotropic regulation through interactions with neural and glial elements.

Animals↗

PubMed1987

Retrograde labeling of neurones in the brain stem following injections of [3H]choline into the forebrain of the rat.

In an attempt to identify cholinergic neurons of the brain stem which project to the forebrain, retrograde labeling of neurons in the brain stem was examined by autoradiography following injections of 20 microCi [3H]choline into the thalamus, hypothalamus, basal forebrain and frontal cortex. After injections into the thalamus, retrogradely labeled neurons were evident within the lateral caudal mesencephalic and dorsolateral oral pontine tegmentum (particularly in the laterodorsal and pedunculopontine tegmental nuclei) and in smaller number within the latero-medial caudal pontine (Reticularis pontis caudalis, Rpc) and medullary (Reticularis gigantocellularis, Rgc) reticular formation. Following [3H]choline injections into the lateral hypothalamus and into the basal forebrain, retrogradely labeled neurons were localized in the dorsolateral caudal midbrain and oral pontine tegmentum and in smaller number in the medial medullary reticular formation (Rgc), as well as in the midbrain, pontine and medullary raphe nuclei. After injections into the anterior medial frontal cortex, a small number of retrogradely labeled cells were found in the brain stem within the laterodorsal tegmental nucleus and the dorsal raphe nucleus. In a parallel immunohistochemical study, choline acetyltransferase (ChAT)-positive neurons were found to be located in most of the regions of the reticular formation where cells were retrogradely labeled from the forebrain following [3H]choline injections. These results suggest that multiple cholinergic neurons within the lateral caudal midbrain and dorsolateral oral pontine tegmentum and a few within the caudal pontine and medullary reticular formation project to the thalamus, hypothalamus and basal forebrain and that a limited number of pontine cholinergic neurons project to the frontal cortex.

Animals↗

PubMed1987

Ultrastructural organization of regenerated serotonin axons in the dorsomedial hypothalamus of the adult rat.

The ultrastructural organization of regenerated serotonin (5-HT) axons was examined in the dorsomedial hypothalamus (DMH) of the adult rat using high-resolution radioautography after intraventricular infusion of [3H]5-HT. An analysis of the microenvironment of the [3H]5-HT-labelled terminals in the DMH was made 30 and 50 days after unilateral injection of 5,7-dihydroxytryptamine (5,7-DHT) or vehicle solution into the dorsolateral hypothalamus. In sham-treated animals [3H]5-HT-labelled axons were small, contained many small clear vesicles, one or more large granular vesicles, and showed only rare synaptic specializations. In 5,7-DHT-treated animals the internal organization of [3H]5-HT-labelled profiles resembled that of sham-treated animals. A tendency toward increased synaptic frequency was found for [3H]5-HT-labelled terminals in the 5,7-DHT-treated group 50 days post-lesion, and an increase in the number of [3H]5-HT-labelled terminals abutting unlabelled perikarya was found in both 30- and 50-day post-lesion groups as compared to sham-treated groups. No other differences in ultrastructural environment were found between sham- and 5,7-DHT-treated animals at either 30 or 50 days post-lesion. These results suggest that 5-HT fibres in the hypothalamus regenerate with a great deal of cellular specificity.

5,7-Dihydroxytryptamine↗

PubMed1987

Distribution of neurotensin binding sites in the caudal brainstem of the rat: a light microscopic radioautographic study.

Specific high-affinity neurotensin binding sites were labeled in sections of the rat caudal brainstem using a monoiodinated ligand, and their distribution was examined by light microscopic radioautography after fixation with glutaraldehyde. In the medulla, labeled binding sites were mainly concentrated within the dorsal motor nucleus of the vagus, the nucleus of the solitary tract, the external cuneate nucleus, the lateral reticular nucleus, the medial vestibular nucleus, the retrofacial nucleus, the linearis nucleus, the paragigantocellular nucleus and the nucleus raphe pallidus. Within the pons, neurotensin binding sites were detected in the reticulotegmental nucleus, the pontine nuclei, the dorsal tegmental nucleus, the laterodorsal and pedunculopontine tegmental nuclei and the nuclei raphe dorsalis and medianus. Most nuclei found here to contain high densities of neurotensin binding sites have been shown to stain intensely for acetylcholinesterase, suggesting a possible association between this enzyme and neurotensin receptors.

Animals↗

PubMed1987

Distribution of neurotensin binding sites in rat brain: a light microscopic radioautographic study using monoiodo [125I]Tyr3-neurotensin.

The topographic distribution of specifically labeled neurotensin binding sites was examined by light microscopic radioautography in rat brain sections incubated with monoiodo [125I]Tyr3-neurotensin. Preliminary experiments indicated that under the present experimental conditions [125I]neurotensin specifically binds to a single apparent population of sites with a dissociation constant of 7.7 +/- 0.3 nM, and that fixation of the labeled sections with glutaraldehyde ensures regionally proportional retention of more than 70% of bound [125I]neurotensin molecules. High concentrations of [125I]neurotensin binding sites were detected in the olfactory bulb and tubercle, parts of the neocortex, the lateral septum, the diagonal band of Broca, the caudate putamen, the amygdala, the dentate gyrus, the anterior dorsal nucleus of the thalamus, the suprachiasmatic nucleus of the hypothalamus, the medial habenula, the zona incerta, the substantia nigra and the ventral tegmental area. In certain areas, such as in the diagonal band of Broca, the substantia innominata, the nucleus basalis and the pars compacta of the substantia nigra, discrete accumulations of silver grains were apparent over neuronal perikarya and their proximal dendrites. In most areas, however, the label appeared more or less uniformly distributed over nerve cell bodies and surrounding neuropil. In several instances, the labeling conformed with the distribution of cell bodies of origin and terminal aborizations of specific projection systems, suggesting that neurotensin receptors might be distributed both proximally and distally on the plasma membrane of certain neurons. Such putative "neurotensinoceptive" projection systems might involve part of the mesostriatal, mesocortical and mesolimbic dopamine systems, as well as the raphe-prosencephalic serotonin system and the habenulo-interpeduncular and basal forebrain-cortical cholinergic systems. Finally, areas of dense [125I]neurotensin labeling often corresponded to zones previously shown to exhibit intense acetylcholinesterase staining, suggesting the existence of a possible link between the expression of neurotensin binding sites and that of acetylcholinesterase in certain neuronal populations.

Animals↗