Neuropeptide receptors in developing and adult rat spinal cord: An in vitro quantitative autoradiography study of calcitonin gene-related peptide,neurokinins, μ-opioid,galanin, somatostatin,neurotensin and vasoactive intestinal polypeptide receptors

A number of neuroactive peptides including calcitonin gene-related peptide (CGRP), substance P, neurokinin B, opioids, somatostatin (SRIF), galanin, neurotensin and vasoactive intestinal polypeptide (VIP) have been localized in adult rat spinal cord and are considered to participate either directly and/or indirectly in the processing of sensory, motor and autonomic functions. Most of these peptides appear early during development, leading to the suggestion that peptides, in addition to their neurotransmitter/neuromodulator roles, may possibly be involved in the normal growth and maturation of the spinal cord. To provide an anatomical substrate for a better understanding of the possible roles of peptides in the ontogenic development of the cord, we investigated the topographical profile as well as variation in densities of [¹²⁵I]hCGRPα, [¹²⁵I]substance P/neurokinin-1 (NK-1), [¹²⁵I]eledoisin/neurokinin-3 (NK-3), [¹²⁵I]FK 33–824 ([D-Ala², Me-Phe⁴, Met(O)ol⁵]enkephalin)/μ-opioid, [¹²⁵I]galanin, [¹²⁵I]T₀D₈-SRIF₁₄ (an analog of sornatostatin), [¹²⁵I]neurotensin and [¹²⁵I]VIP binding sites in postnatal and adult rat spinal cord using in vitro quantitative receptor autoradiography. Receptor binding sites recognized by each radioligand are found to be distributed widely during early stages of postnatal development and then to undergo selective modification to attain their adult profile of distribution during the third week of postnatal development. The apparent density of various receptor sites, however, are differently regulated depending on the lamina and the stage of development studied. For example, the density of μ-opioid binding sites, following a peak at postnatal day 4 (N), declines gradually in almost all regions of the spinal cord with the increasing age of the animal [¹²⁵I]substance P/NK-1 binding sites, on the other hand, show very little variation until P14 and then subsequently decrease as the development proceeds. In the adult rat, most of these peptide receptor binding sites are localized in relatively high amounts in the superficial laminae of the dorsal horn. To varying extents, moderate to low density of various peptide receptor binding sites are also found to be present in the ventral horn, intermediolateral cell column and around the central canal. Taken together, these results suggest that each receptor-ligand system is regulated differently during development and may each uniquely be involved in cellular growth, differentiation and in maturation of the normal neural circuits of the spinal cord, Furthermore, the selective localization of various receptor binding sites in adult rat spinal cord over a wide variety of functionally distinct regions reinforces the neurotransmitter/ modulator roles of these peptides in sensory, motor and autonomic functions associated with the spinal cord. © 1995 Wiley-Liss, Inc.     

Altered Calcitonin Gene-related Peptide, Substance P and Enkephalin Immunoreactivities and Receptor Binding Sites in the Dorsal Spinal Cord of the Polyarthritic Rat

The dorsal horn of the spinal cord, which forms the locus of first synapses in pain pathways, is an important site of interaction between calcitonin gene-related peptide (CGRP), substance P and enkephalin—the neuropeptides considered to be especially involved in the regulation of pain perception. Since adjuvant-induced arthritic rats provide a suitable model for peripheral inflammation and hyperalgesia, the possible alterations of immunoreactive CGRP, substance P and enkephalin as well as the binding sites for [¹²⁵I]hCGRPα, [¹²⁵I]substance Plneurokinin-1, (NK1) and [¹²⁵I]FK-33-824/μ-opioid receptors were studied in the dorsal horn of the spinal cord receiving projections from the inflamed limbs. In arthritic rats compared to control animals, a bilateral increase in CGRP- and substance P-immunoreactive fibres and the presence of enkephalin-immunoreactive cell bodies were noted in the dorsal horn of the spinal cord. As for receptors, while a significant decrease in [¹²⁵I]hCGRPα and [¹²⁵I]substance P/NK1 binding sites was observed in selective layers, no measurable alteration in [¹²⁵I]FK-33-824/μ-opioid binding sites was noted in any regions of the arthritic rat dorsal horn compared to the unaffected control rats. Following unilateral section of the peripheral nerve prior to induction of arthritis, CGRP- and substance P-immunoreactive fibres were markedly depleted and no enkephalin-positive neurons were observed in the ipsilateral dorsal horn. Analysis of receptor binding sites in denervated arthritic rats, however, exhibited differential responses, i.e. a significant increase in [¹²⁵I]hCGRPα, a marked decrease in [¹²⁵I]FK-33-824/μ-opioid and apparently no alteration in [¹²⁵I]substance P/NK1 receptor binding sites were observed in the ipsilateral dorsal horn compared to the intact contralateral side. These results taken together provide anatomical evidence for a concerted role of these peptides in the regulation of adjuvant-induced hyperalgesia accompanying peripheral inflammation.     

Autoradiographic Localization of Receptors in the Cochlear Nucleus of the Mouse

Light microscopic autoradiography of bound radiolabeled ligands was used to describe the distribution of six receptor types in the dorsal and ventral mouse cochlear nuclei: Glycine receptor ([³H]strychnine); GABA receptor (³H]muscimol); benzodiazepine receptor ([³H]flunitrazepam); adenosine receptor ([³H]cyclohexyladenosine); muscarinic ACh receptor ([³H]quinuclidinyl benzilate); histamine receptor ([³H]mepyramine). The most intense [³H]strychnine labeling was observed in the deep region of the dorsal cochlear nucleus (DCN), with slightly lower levels in the molecular and pyramidal layers. Highest density of [³H]muscimol binding sites was observed in the granule cell layer of the posterior ventral nucleus (PVCN) and in the pyramidal layer of the DCN. Diffuse [³H]flunitrazepam labeling was distributed over all laminar regions of the DCN; the highest grain density was observed over the granule cell layer of the PVCN. Intense [³H]cyclohexyladenosine labeling was seen over the molecular layer, possibly extending into the pyramidal layer, of the DCN. The granule cell layer of the PVCN was also densely labeled. High concentrations of [³H]qiuinuclidinyl benzilate sites were seen in the molecular layer, possibly extending into the pyramidal layer, of the DCN. A thin band of high grain density was also visible over the granule cell layer of the PVCN. Moderate, diffuse [³H]mepyramine labeling was visible throughout the DCN, with slightly higher grain density over the molecular and possibly the pyramidal layers, than over the deep region of the DCN.     

Distribution,of [3H]quinuclidinyl benzilate, [3H]nicotine,and [125I]alpha-bungarotoxin binding sites in the nucleus tractus solitarii of the cat

The distribution of muscarinic and nicotinic cholinergic binding sites in the cat nucleus tractus solitarii was studied by the technique of in vitro autoradiography. Using the antagonist [³H]quinuclidinyl benzilate, muscarinic binding sites were differentially located in subdivisions of the nucleus tractus solitarii. The majority of muscarinic binding sites were located predominantly in the caudal half of the nucleus, reaching their greatest amounts at the mid levels of the nucleus tractus solitarii. The medial, dorsolateral, intermediate, and interstitial subdivisions contained the highest densities of quinuclidinyl benzilate binding sites. Nicotinic cholinergic binding sites, using [³H]nicotine and [¹²⁵I]alpha-bungarotoxin, had unique patterns of distribution. With [³H]nicotine the majority of binding sites were located in rostral levels of the nucleus with very few binding sites present in the caudal half. In contrast, [¹²⁵I]alpha-bungarotoxin binding sites were present mainly in subdivisions located in the caudal half of the nucleus, i.e., commissural, ventrolateral, dorsolateral, medial, and intermediate subdivisions, and dropped off precipitously at more rostral levels. The differential distribution of [³H]nicotine and [¹²⁵I]alpha-bungarotoxin suggests the two ligands may be labeling different types of nicotinic binding sites in the nucleus tractus solitarii. The unique distribution of muscarinic and nicotinic cholinergic binding sites in the various subdivisions of the nucleus solitarii suggests that muscarinic and nicotine mechanisms may play an active role in the regulation of the diverse autonomic functions at the level of the nucleus tractus solitarii. © 1993 Wiley-Liss, Inc.     

Biochemical characterization and autoradiographic localization of central substance P receptors using [I]physalaemin

The binding of [¹²⁵I]physalaemin to rat brain slices was investigated. Radiolabeled physalaemin bound with high affinity (K_d = 0.3 nM) to a single class of sites (B_max = 22 fmol/mg protein). Kinetic studies indicated that binding was time-dependent and all specific binding was reversible. Pharmacology studies indicated that specific [¹²⁵I]physalaemin binding was inhibited by structurally related peptides such as substance P and eledoisin. Biochemical studies indicated that specific binding of radiolabeled physalaemin was greatly reduced if the brain slices were pretreated with heat, trypsin or N-ethyl maleimide. Autoradiographic studies indicated that the [¹²⁵I]physalaemin binding sites were discretely distributed throughout the brain. Highest grain densities were present in the olfactory bulb, dentate gyrus, amygdala, superficial layers of the superior colliculus, subiculum, dorsal parabrachial nucleus, locus coeruleus, nucleus tractus solitarii and dorsal horn of the spinal cord. Moderate grain densities were present in the nucleus accumbens, olfactory tubercle, pyriform cortex, striatum, hippocampus, inferior colliculus and central gray of the midbrain. Low grain densities were present in most thalamic nuclei, the substantia nigra and cerebellum. The corpus callosum and controls treated with 1 μM unlabeled physalaemin had negligible levels of binding. The unique pharmacological and regional distribution data obtained suggest that [¹²⁵I]physalaemin may serve as a valuable probe to study central substance P receptors.     

[H]substance P binding in the intermediolateral cell column and striatum of the rat

[³H]substance P binding was studied in the intermediolateral cell column and striatum in the rat using slide-mounted sections. The intermediolateral cell column had a single high affinity binding component with a dissociation constant,K_d = 1.45 nM and the number of sites,B_max= 18.1fmol per mg protein. The striatum had aK_d = 0.77nM and aB_max= 23.5fmol per mg protein. The relative potency of various substance P-like tachykinins in displacing [³H]substance P suggested that both these areas may contain a substance P-P (for physalaemin) receptor subtype. (d-Pro⁴,d-Trp^7,9)substance P(4–11), a substance P antagonist, has a relatively low affinity (micromolar range) in both these areas.     

Phylogenetic distribution of bicuculline-sensitiveγ-amino-butyric acid (GABA) receptor binding

Bicuculline-sensitive [³H]GABA receptor binding was studied in membrane fractions prepared from vertebrate whole brain or invertebrate cephalic ganglia. In tissue not treated with Triton X-100, a significant amount of bicuculline-displaceable [³H]GABA binding was detected in the brains of all vertebrates studied, with the hagfish brain binding over twice as much [³H]GABA as the spiny dogfish, the next oldest species. All other vertebrates bound similar amounts of [³H]GABA, being one-third to one-fourth that observed in the hagfish. In contrast, after Triton treatment, the hagfish displayed the least amount of bicuculline-sensitive [³H]GABA binding and, under those conditions, the amount of binding observed increased in an evolutionary fashion. No measurable bicuculline-sensitive GABA receptor binding was noted in any invertebrate studied. These results suggest that bicuculline-sensitive GABA receptors are present in the brains of all vertebrates and that during the course of evolution there developed a Triton-sensitive substance(s) whose presence modifies the kinetic properties of this receptor site.     

Effect of neutral endopeptidase inhibitors on H-substance P binding in rat lleum

To determine whether neutral endopeptidase regulates the binding of substance P to the receptors, and if so, what the mechanism is, we determined the effect of neutral endopeptidase inhibitors, thiorphan and phosphoramidon, on specific binding of ³H-substance P to homogenates of rat ileum. Specific binding was of high affinity and was saturable (dissociation constant, K_D = 2.4 ± 0.17 nM and number of maximal binding sites, B_max = 101.1 ± 5.5 fmol/mg protein), and the receptor subtype was substance P-P type. Neutral endopeptidase inhibitors increased the specific binding to up to 160% of control (P < 0.005). Neutral endopeptidase inhibitors prevented the degradation of ³H-substance P during the binding assay and increased the amount of ³H-substance P remaining in the assay system to up to 4.5-fold of control (P < 0.005), but did not significantly change the K_D or B_max values of specific binding. Protease inhibitors of kininase II, serine proteinases, or thiol proteinases did not significantly change either specific binding or the amount of ³H-substance P remaining in the assay system. We conclude that neutral endopeptidase regulates the binding of substance P to the receptors and that it does so by decreasing the amount of substance P available to the receptors, without significantly changing the affinity or the number of receptors.     

Anatomical distribution of mu,delta, and kappa opioid- and nociceptin/orphanin FQ-stimulated [35S]Guanylyl-5′-O-(γ-Thio)-triphosphate binding in guinea pig brain

An in vitro autoradiographic technique has recently been developed to visualize receptor-activated G-proteins by using agonist-stimulated [³⁵S]guanylyl-5′-O-(γ-thio)-triphosphate ([³⁵S]GTPγS) binding in the presence of excess guanosine 5′-diphosphate. This technique was used to localize opioid-activated G-proteins in guinea pig brain, a species that contains the three major types of opioid receptors. This study used selective μ, δ, and κ opioid agonists as well as nociceptin or orphanin FQ (N/OFQ) peptide, an endogenous ligand for an orphan opioid receptor-like (ORL1) receptor, to stimulate [³⁵S]GTPγS binding in guinea pig brain sections. Opioid receptor specificity was confirmed by blocking agonist-stimulated [³⁵S]GTPγS binding with the appropriate antagonists. In general, the distribution of agonist-stimulated [³⁵S]GTPγS binding correlated with previous reports of receptor binding autoradiography, although quantitative differences suggest regional variations in receptor coupling efficiency. Mu, δ, and κ opioid-stimulated [³⁵S]GTPγS binding was found in the caudate-putamen, nucleus accumbens, amygdala, and hypothalamus. Mu-stimulated [³⁵S]GTPγS binding predominated in the hypothalamus, amygdala, and brainstem, whereas κ-stimulated [³⁵S]GTPγS binding was particularly high in the substantia nigra and cortex and was moderate in the cerebellum. N/OFQ-stimulated [³⁵S]GTPγS binding was highest in the cortex, hippocampus, and hypothalamus and exhibited a unique anatomical distribution compared with opioid-stimulated [³⁵S]GTPγS binding. The present study extends previous reports on opioid and ORL1 receptor localization by anatomically demonstrating functional activity produced by μ, δ, and κ opioid and ORL1 receptor activation of G-proteins. J. Comp. Neurol. 386:562–572, 1997. © 1997 Wiley-Liss, Inc.     

Differential number of glycine- and GABA-immunopositive neurons and terminals in the deep cerebellar nuclei of normal and Purkinje cell degeneration mutant mice

The total number of glycine-immunopositive (Gly⁺) neurons in the deep cerebellar nuclei (DCN) was quantified under normal conditions in wild-types (B6C3Fe) and compared with the Purkinje cell-deprived situation in Purkinje cell degeneration (PCD)-mutants by using an unbiased stereological method, the disector. In addition, the size and density of Gly⁺ terminals, the number of γ-aminobutyric acid immunopositive (GABA⁺) somata and the somatal colocalization of Gly and GABA were determined. In both wild-types and PCD mutants, Gly⁺ somata are distributed relatively homogeneously among the different subdivisions of the DCN. However, in the complete volume of the DCN, which is reduced in PCD mutants by 52%, 8,582 Gly⁺ neuronal somata are present in wild-types and 14,637 in PCD mutants, which corresponds to an increase of 70.5% in the mutant. In contrast, the total number of GABA⁺ somata is almost the same in wild-types (16,713) and in PCD mutants (15,339). The number of neurons that colocalize both Gly and GABA is again almost identical in wild-types (3,976) and PCD mutants (3,861). Moreover, the size and number of Gly⁺ terminals contacting DCN neurons of PCD mutants are increased significantly compared to the wild-types. These data define for the first time the normal distribution of glycine and its somatal colocalization with GABA in the DCN of the mouse. In addition, it is shown that the Purkinje cell loss in PCD mutants leads to a significant increase in Gly⁺ somata and to a larger size and number of Gly⁺ boutons in the DCN. This suggests that the respective neurons are capable of exerting an enhanced inhibitory synaptic activity on their target neurons, substituting, at least in part, for the lost Purkinje cell (PC) inhibition. Probable correlations of these findings with the mildness of the motor disturbances found in PCD mutants are discussed. J. Comp. Neurol. 382:443-458, 1997. © 1997 Wiley-Liss Inc.     

Axonal transport of opiate receptors in capsaicin-sensitive neurones

Opiate receptors measured in vitro or in vivo with [³H]lofentanil in the rat vagus nerve were found to accumulate on both sides of a ligature, thus indicating a bidirectional axoplasmic transport of these receptors. When rats were treated with capsaicin, the accumulation of opiate receptors was tremendously reduced in the vagus whereas muscarinic receptors in ligated sciatic nerves were unaffected. Since capsaicin is known to affect sensory neurones, mostly those containing substance P, the present results support the idea that the opiate receptors in the vagus are associated with substance P neurones.     

Development of MK-801, kainate,AMPA, and muscimol binding sites and the effect of dark rearing in rat visual cortex

We used quantitative autoradiography to determine whether the development of glutamate receptors correlates with the plastic period for monocular deprivation in rat visual cortex. To study glutamate receptors, we incubated sections of rat visual cortex with tritiated (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10imine maleate (MK-801), tritiated kainate, and tritiated amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA). [³H]MK-801 is a noncompetitive ligand for the N-methyl-D-aspartate (NMDA) receptor. [³H]kainate and [³H]AMPA are competitive ligands for non-NMDA receptors. To compare glutamate binding sites with a nonglutamate binding site, we studied [³H]muscimol, which binds to γ-aminobutyric acid (GABA)_A receptors. [³H]MK-801 binding was maximal at postnatal day 26 (P26) and decreased in adulthood. [³H]AMPA binding was maximal at P18. [³H]kainate binding and [³H]muscimol binding were not age dependent. Dark rearing partially prevented the age-dependent decrease in [³H]MK-801 binding but had no effect on [³H]kainate or [³H]AMPA binding. Dark rearing decreased muscimol binding in adult animals. These results suggest that NMDA receptors, but not other glutamate receptors or GABA_A receptors, are likely to be critical for developmental plasticity in rat visual cortex. J. Comp. Neurol. 383:73–81, 1997. © 1997 Wiley-Liss, Inc.     

Autoradiographic distribution of [3H]YM-09151-2, a high-affinity and selective antagonist ligand for the dopamine D2 receptor group,in the rat brain and spinal cord

We determined the regional distribution of the dopamine D₂ receptor group in the rat central nervous system by quantitative receptor autoradiography with a high-affinity and selective antagonist, [³H]YM-09151-2. Saturation and competition experiments demonstrated that the binding of [³H]YM-09151-2 to striatal sections was saturable (Bmax=37.3 fmol/section), of high affinity (Kd=0.315 nM), and was inhibited selectively by prototypic D₂ ligands. The anatomical localization of binding sites was determined by comparison of autoradiograms and the original ³H-ligand-exposed sections stained with cresyl violet. Very high levels of [³H] YM-09151-2 binding were found in the caudate-putamen, nucleus accumbens, tuberculum olfactorium and the insula of Calleja, to each of which midbrain dopaminergic neurons project densely. High levels of binding were also observed in other regiions rich in dopaminergic neurons and fibers including the glomerular layer of the olfactory bulb, the intermediate lobe of the pituitary, lateral septum, substantia nigra pars compacta, interfascicular nucleus, dorsal raphe nucleus, locus coeruleus, and nucleus of the solitary tract. Some regions poor in dopaminergi innervation, however, had high levels of [³H]YM-09151-2 binding including the molecular layer of gyrus dentatus, all layers of CA1 and the nonpyramidal layer of CA4 of hippocampus, and the deeper layer of medial entorhinal cortex. Motor neurons present in brainstem motor nuclei and spinal ventral horn were also strongly labeled. Neocortical, cerebellar, and thalamic regions had low levels of binding, except lobules 9–10 of the cerebellum, the olivary pretectal nucleus, zona incerta and lateral mammillary nucleus, in which moderate to high levels of binding were detected. Our findings concerning the widespread but region-specific localization of [³]YM-09151-2 binding sites in the brain and spinal cord may prove useful for analyzing varoius dopaminergic functions in the central nervous system. © 1994 Wiley-Liss, Inc.     

Substance P receptor desensitization in the dorsal horn: possible involvement of receptor-G protein complexes

The repeated administration of a high dose of substance P (SP) onto the spinal cord has been shown to attenuate behavioral response to an intense heat (tail-flick) or noxious mechanical stimulus (paw pressure). Studies performed to investigate the action of spinal SP have suggested that changes in behavioral responses involve endogenous opiate or neurokinin systems. This study was performed to investigate whether the binding characteristics of SP receptors in the dorsal horn are altered following successive administration of SP. Two populations of [³H]-SP binding sites were distinguished on the basis of their binding affinity. Gpp(NH)p, a stable analogue of GTP, decreased the size and affinity of the high affinity binding component selectively labelled with [¹²⁵I]-Bolton Hunter-SP. Repeated intratehcal administration of SP (15 μg) which reduced behaviors also reduced the number and affinity binding sites. Thus, attenuated behaviors in response to repeated administration of SP are paralleled by an alteration of SP binding in the dorsal horn. The altered agonist affinity seen under desensitizing conditions raises the possibility that SP receptor desentization involves an uncoupling of receptor-G protein complexes.     

Receptor-mediated calcium signalling in glial cells from mouse corpus callosum slices

We addressed the question of whether glial cells in intact white matter tracts express neurotransmitter receptors and we used Ca⁺⁺ signalling as a probe to detect the receptor activation. Corpus callosum slices from postnatal mice were bulk-loaded with the Ca⁺⁺- sensitive fluorescent dye fluo-3, and confocal microscopy was used to measure Ca⁺⁺ transients in response to neuroligands. Glial cell bodies were intensely dye-loaded and could be discriminated from the diffuse fluorescence of axons. Subpopulations of glial cells from slices obtained at postnatal days 3 to 7 responded with Ca⁺⁺ signals to ATP, glutamate, histamine, GABA, norepinephrine, serotonin, angiotensin II, bradykinin, and substance P. These subpopulations showed a distinct overlap; cells which were responsive to substance P always showed Ca⁺⁺ signalling in response to histamine, ATP, GABA, and high K⁺ (membrane depolarization). GABA-responsive cells almost always showed a [Ca⁺⁺], increase after membrane depolarization. In brain slices from postnatal day 11 to 18 animals, the Ca⁺⁺ responses were evident for glutamate, ATP, and norepinephrine, while GABA, substance P, serotonin, histamine, or angiotensin II rarely elicited a response. This study demonstrates that white matter glial cells in slices exhibit a large repertoire of neurotransmitter responses linked to Ca⁺⁺ signalling and that these receptor systems are differentially distributed on sub-populations of glial cells. © 1996 Wiley-Liss, Inc.     

Differential distribution of synaptic endings containing glutamate, glycine, and GABA in the rat dorsal cochlear nucleus

The dorsal cochlear nucleus (DCN) integrates the synaptic information depending on the organization of the excitatory and inhibitory connections. This study provides, qualitatively and quantitatively, analyses of the organization and distribution of excitatory and inhibitory input on projection neurons (fusiform cells), and inhibitory interneurons (vertical and cartwheel cells) in the DCN, using a combination of high-resolution ultrastructural techniques together with postembedding immunogold labeling. The combination of ultrastructural morphometry together with immunogold labeling enables the identification and quantification of four major synaptic inputs according to their neurotransmitter content. Only one category of synaptic ending was immunoreactive for glutamate and three for glycine and/or gamma-aminobutyric-acid (GABA). Among those, nine subtypes of synaptic endings were identified. These differed in their ultrastructural characteristics and distribution in the nucleus and on three cell types analyzed. Four of the subtypes were immunoreactive for glutamate and contained round synaptic vesicles, whereas five were immunoreactive for glycine and/or GABA and contained flattened or pleomorphic synaptic vesicles. The analysis of the distribution of the nine synaptic endings on the cell types revealed that eight distributed on fusiform cells, six on vertical cells and five on cartwheel cells. In addition, postembedding immunogold labeling of the glycine receptor alpha1 subunit showed that it was present at postsynaptic membranes in apposition to synaptic endings containing flattened or pleomorphic synaptic vesicles and immunoreactive for glycine and/or GABA on the three cells analyzed. This information is valuable to our understanding of the response properties of DCN neurons.     

Opioid receptor ligand binding in the human striatum: II. Heterogeneous distribution of kappa opioid receptor labeled with [3H]Bremazocine

Selective kappa opioid receptor autoradiography with [³H]bremazocine (BRM) was used to examine regional and subregional kappa receptor distribution patterns at five rostrocaudal levels through the human striatum. [³H]BRM binding densities were measured in the individual striatal nuclei and in subregions therein. The distribution of [³H]BRM binding sites was found to have a strongly heterogeneous character. At the regional level a rostral-to-caudal decrease in [³H]BRM binding densities was observed. Also, a dorsal-to-ventral differentiation was seen, with higher values in the ventral striatum, especially in the nucleus accumbens, and lower values in the dorsal parts of the caudate nucleus and putamen. These findings suggest an association of kappaa receptor function with limbic-related processes in the ventral striatum. Along the ventral edge of the nucleus accumbens and putamen, specific domains with extremely high [³H]BRM binding values were identified. © 1996 Wiley-Liss, Inc.     

Occurrence and distribution of substance P receptors in the cerebral blood vessels of the rat

The distribution of immunoreactivity to the receptor for substance P was examined in the cerebral blood vessels of the rat. Substance P immunoreactivity has been demonstrated in the nerve fibers of the cerebral blood vessels. Recently, the production of substance P receptor specific antibody has enabled the detection of localization of the substance P receptor in the central nervous system. In this study, we examined the existence of nerve fibers with substance P receptor immunoreactivity in the cerebral blood vessels and the cranial ganglia innervating the cerebral blood vessels. Sprague–Dawley rats were perfused with fixative and the pial arteries and the cranial ganglia known to innervate the cerebral blood vessels, i.e., trigeminal, sphenopalatine, internal carotid, otic and superior cervical ganglia, were dissected. All specimens were incubated with anti-substance P receptor IgG, then stained by the avidin–biotin–peroxidase complex method. Numerous nerve fibers with varicosities forming plexuses, with substance P receptor immunoreactivity were observed on the walls of the major extracerebral arteries forming the circle of Willis and its branches. Substance P receptor immunoreactivity was also detected in the endothelium of the cerebral arteries. Substance P receptor immunoreactivity was positive in many neurons of the sphenopalatine ganglion, otic ganglion, trigeminal ganglion, superior cervical ganglion and internal carotid ganglion. The present study demonstrated the existence of nerve fibers with substance P receptor immunoreactivity in the cerebral blood vessels and the cranial ganglia that innervate the cerebral blood vessels. These findings are important in understanding the responsiveness of the cerebral blood vessels to substance P.     

Species differences in the expression and distribution of the neuropeptide Y Y1, Y2, Y4, and Y5 receptors in rodents,guinea pig,and primates brains

The respective distribution of neuropeptide Y Y₁, Y₂, Y₄, and Y₅ receptor subtypes was investigated in rodents (rat and mouse), guinea pig, and primates (marmoset and vervet monkeys and human) brains, representing three orders of mammals. [¹²⁵I][Leu³¹,Pro³⁴]PYY (total Y₁-like; Y₁, Y₄, and Y₅) and [¹²⁵I]PYY_3–36 (total Y₂-like; Y₂ and possibly Y₅) binding sites were discretely but similarly distributed in the rat and mouse brain, each having its unique pattern. In contrast, surprisingly low levels of [¹²⁵I]PYY_3–36 binding sites were found in the guinea pig brain including in the hippocampal formation. [¹²⁵I][Leu³¹,Pro³⁴]PYY/BIBP3226-insensitive binding sites (Y₅-like) were found in different areas of the rat and guinea pig brains. The primate brains also revealed a different distribution binding profile for these various NPY receptor subtypes. Although the human and vervet brains contained very low amounts of [¹²⁵I][Leu³¹,Pro³⁴]PYY sites (Y₁-like) in most brain regions, except for the dentate gyrus of the hippocampus, the marmoset brain contains significant amounts of both [¹²⁵I][Leu³¹,Pro³⁴]PYY (Y₁-like) and [¹²⁵I]PYY_3–36 (Y₂-like) binding sites. Additionally, [¹²⁵I][Leu³¹,Pro³⁴]PYY/BIBP3226-insensitive binding sites were not clearly detected in the vervet and human brains. On the other hand, Y₅-like binding sites were observed in few regions of the marmoset brain. Finally, [¹²⁵I]hPP (Y₄/Y₅-like) were very discretely distributed in the rat brain, being concentrated in the paraventricular nucleus of the hypothalamus and the interpeduncular nucleus. The marmoset brain is apparently not enriched with specific [¹²⁵I]hPP sites. Taken together, these data show that significant species differences exist in the level of expression and distribution of various NPY receptor subtypes in the mammalian brain. J. Comp. Neurol. 402:372–384, 1998. © 1998 Wiley-Liss, Inc.