Vasoactive Intestinal Polypeptide Binding Sites Research Articles

Developmental Pattern of VIP Binding Sites in the Human Hypothalamus

We have studied the developmental patterns of vasoactive intestinal polypeptide (VIP) binding sites in the human hypothalamus. VIP recognition sites were widely distributed throughout the rostrocaudal extent of the hypothalamus. VIP binding was generally low in the fetal and neonatal periods and a tendency in increasing densities was observed during postnatal development. The age comparison of binding density indicates variations in several structures. Thus, the densities were higher in older infants in the preoptic area, lamina terminalis, and infundibular (IN) nucleus. These differences suggest the implication of VIP receptors in the development of this brain structure and the maintenance of its various functions.

Expression and Distribution of Vasoactive Intestinal Polypeptide Receptor VPAC2 mRNA in Human Airways

Vasoactive intestinal polypeptide (VIP) is a putative neurotransmitter of the inhibitory non-adrenergic non-cholinergic nervous system and influences many aspects of mammalian airway function. VIP binds to two G-protein-coupled VPAC receptors that are highly homologous structurally but distinguished by their different affinities for peptide analogues of VIP. As VIP binding sites in the respiratory tract have only been examined by ligand binding and cytochemical techniques, we studied the distribution of the mRNA that encodes the inducible receptor subtype VPAC2 in the human respiratory tract. Northern blots demonstrated the expression of VPAC2 mRNA in human airways and other tissues. A human-specific VPAC2 cRNA probe was used to detect VPAC2 mRNA expression in human lung by nonradioactive in situ hybridization. In larger airways, positive VPAC2 mRNA signals were localized to tracheal and bronchial ciliated epithelial cells. There was also marked staining of mucous and serous cells of submucosal glands. No signals were obtained in airway and vascular smooth muscle myocytes and endothelial cells. In peripheral lung tissues, VPAC2 mRNA expression was localized to epithelial cells of the bronchioles. Specific staining was detected in immune cells and alveolar macrophages. In summary, VPAC2 is localized in airway epithelial, glandular, and immune cells of the lung but not in airway and vascular smooth muscle. The absence of VPAC2 mRNA in vascular and airway smooth muscle myocytes may indicate that the effects of VIP on vasodilation and bronchodilation are mediated by VPAC1 or undefined receptors. However, a paracrine modulation of the two most prominent effects of VIP in the respiratory tract by VPAC2 cannot be excluded.

Region-specific antiproliferative effect of VIP and PACAP-(1-38) on rabbit enteric smooth muscle.

The ability of neuropeptides to modulate enteric smooth muscle proliferation was examined in primary explant cultures of rabbit gastric antrum and colon smooth muscle. Cell proliferation was determined by [3H]thymidine incorporation measurements and cell counting. Subcultured rabbit antrum and colon myocytes (passages 2-6) preserved a smooth muscle phenotype, as verified by immunohistochemistry for alpha-smooth muscle actin and electron microscopy. Both vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating peptide-(1-38) [PACAP-(1-38)] concentration dependently (10(-10) to 10(-6) M) inhibited the serum-induced [3H]thymidine incorporation [in colon, 48.2 +/- 5.8 and 55.6 +/- 9.3% of control with 10(-6) M VIP and 10(-7) M PACAP-(1-38)] and inhibited increase in cell numbers in cultures derived from the colon but not in those from the antrum. Effects of VIP and PACAP-(1-38) were mimicked by forskolin (10(-7) to 10(-6) M) but not by 8-bromo-cGMP, whereas theophylline enhanced the effects of VIP. Inhibition of nitric oxide synthase with NG-nitro-L-arginine methyl ester (10(-3.5) M) did not alter the effects of VIP. Substance P, motilin, calcitonin gene-related peptide, and somatostatin had no effect. A single class of 125I-labeled VIP binding sites was found in antrum and colon myocyte cultures with an equal affinity for VIP and PACAP-(1-38) [dissociation constant (Kd) in antrum = 3.4 +/- 0.8 nM for VIP and 2.0 +/- 1.0 nM for PACAP-(1-38); Kd in colon = 2.0 +/- 1.0 nM for VIP and 2.8 +/- 1.6 nM for PACAP-(1-38)]. Density of binding sites in the antrum was higher than in the colon. In disease states such as inflammatory bowel disease, inhibition of myocyte proliferation by VIP and PACAP may serve to control smooth muscle hyperplasia in the colon but not in the antrum.

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]hCGRP alpha, [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)/mu-opioid, [125I]galanin, [125I]T0D8-SRIF14 (an analog of somatostatin); [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 mu-opioid binding sites, following a peak at postnatal day 4 (P4), 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.

The Distribution and Density of Airway Vasoactive Intestinal Polypeptide (VIP) Binding Sites in Cystic Fibrosis and Asthma

Summary: The densities of airway binding sites for Vasoactive intestinal polypeptide (VIP) were determined using 125I-labelled VIP (IVIP) and the technique of autoradiography applied to cryostat sections. Tissue studied included: grossly normal airway tissue taken from lungs resected for bronchial carcinoma (Ca; n=11) and lungs removed at transplant from patients with cystic fibrosis (CF; n=7). Lung tissue obtained at post-mortem in cases of fatal asthma (n=3) or lobes resected for bronchiectasis (n=3) were taken as further disease controls. In the Ca controls there was dense IVIP labelling, of alveolar wall, blood vessels, airway epithelium, submucosal glands, and bronchial smooth muscle: labelling of bronchiolar smooth muscle was sparse. In comparison with the Ca controls, IVIP labelling of all tissue structures in CF, with the exception of bronchial smooth muscle, was reduced ( P<0.01). The most striking reductions were associated with airway epithelium and alveolar wall. These reductions showed a similar trend in bronchiectasis but did not achieve statistical significance. There was no such change in lung tissue obtained from the cases of fatal asthma where labelling of bronchial smooth muscle and all other structures was similar to that of the Ca controls. It is likely that the reduction of VIP binding sites in CF is secondary to infection and inflammation.

Localization and developmental pattern of vasoactive intestinal polypeptide binding sites in the human hypothalamus

Using a quantitative in vitro autoradiographic approach, vasoactive intestinal polypeptide (VIP) binding site densities were compared in the post-mortem hypothalamus of human neonate/infant and adult. The densities were similar during development in most of the hypothalamic nuclei and areas examined underlying the stability of 125I-VIP binding sites in the post-mortem hypothalamus of young and adult individuals. However, the ventral part of the medial preoptic area, the medial, lateral, and supramammillary nuclei were characterized by an increase of 125I-VIP binding with age. In young and adult individuals, the highest densities of hypothalamic 125I-VIP binding sites were detected in the supraoptic and infundibular nuclei; the ependyma; the organum vasculosum of the lamina terminalis; the horizontal limb of the diagonal band of Broca; the ventral part of the medial preoptic area (in adult); the suprachiasmatic, paraventricular, and periventricular nuclei; and the medial and lateral mammillary nuclei in adult. Moderate densities were found in the vertical limb of the diagonal band of Broca, the bed nucleus of the stria terminalis, the ventral part of the medial preoptic area in neonate/infant, the medial and lateral mammillary nuclei in neonate/infant, the supramammillary nucleus in adult, the dorsal hypothalamic area, and the ventromedial nucleus. Low to moderate binding site densities were observed in the other hypothalamic regions of young or adult individuals. The nonspecific binding ranged from 15% of the total binding in the anterior hypothalamus to 20% in the mediobasal and posterior hypothalamic levels. Taken together, these results provide evidence for a large distribution of VIP binding sites in neonate/infant and adult human hypothalamus suggesting the implication of VIP in the development of this brain structure and the maintenance of its various functions.

Effects of sensitization on vasoactive intestinal polypeptide-induced relaxation and its concentration and binding in guinea-pig airways

We investigated the relaxant effect of vasoactive intestinal polypeptide (VIP) in trachea and lung parenchyma from normal and sensitized guinea-pigs. A technique by which drug access was restricted to either the mucosal or the adventitial surface of tracheal rings was used. In intact trachea, concentration-response curves for VIP entering from the mucosal surface (pD 2 = 6.61 ± 0.06) were displaced to the right compared with those for adventitial entry (pD 2 = 6.78 ± 0.04). Epithelium removal produced a leftward shift (≈ 2.8-fold) in the mucosal VIP concentration-response curve. Sensitization did not alter the responsiveness (maximal effect) or sensitivity (pD 2 values) of tracheal rings to VIP irrespective of the surface of drug entry and of the absence or presence of epithelium. VIP-induced relaxation of normal and sensitized lung strips was also similar. Sensitization resulted in a significant decrease in tracheal VIP content (from 2.16 ± 0.07 in normal to 0.60 ± 0.08 nmol/mg) protein in sensitized trachea; P < 0.05; n = 7 whereas the affinity of both high- and low-affinity binding sites for VIP increased as compared to that of normal trachea. Differences were not found in the binding capacities of normal and sensitized trachea. VIP content and binding did not differ in normal and sensitized lung. In conclusion, immunological sensitization produced changes in VIP tracheal content and binding but neither VIP-induced relaxation of isolated airways nor the influence of epithelium in this response was altered.

Identification of vasoactive intestinal polypeptide (VIP) binding protein in bovine pineal gland

Vasoactive intestinal polypeptide (VIP) containing nerves are present in close proximity to epithelial, endocrine, and vascular smooth muscle cells. The pineal gland, known also as a “neuroendocrine transducer organ” contains a high content of VIP which prompted us to characterize the binding sites for VIP in this organ. [Tyr 10− 125I]VIP was bound selectively and specifically to pineal membrane preparations in a time-dependent fashion. Scatchard analysis demonstrated a single class of high affinity binding sites with a dissociation constant ( K d ) value of 5.7 ± 0.52 nmol/1 and a receptor density ( B max) value of 440 ± 35 fmol/mg protein. A Hill Plot with a slope of 1.013 indicated the absence of cooperativity. Covalent crosslinking with [Tyr 10− 125I]VIP followed by SDS electrophoresis and autoradiography, revealed that the VIP binding protein exhibited a molecular weight of 51.8 ± 0.5 kDa. The precise function of pineal VIP binding protein remains to be delineated.

Demonstration of [ 125I]VIP binding sites and effects of VIP on cAMP-formation in rat insulinoma (RINm5F and RIN14B) cells

Vasoactive intestinal polypeptide (VIP)-immunoreactive nerves have been demonstrated in close association with the islets of Langerhans, and VIP has been shown to stimulate insulin and somatostatin secretion. Using [ 125I]VIP and membranes prepared from rat insulinoma (RIN) cells, i.e., the subclones m5F (m5F; mainly insulin-secreting) and 14B (14B; mainly somatostatin-secreting), it was found that VIP (10 −10–10 −7 M) competitively inhibited the binding of [ 125I]VIP. A single class of high affinity binding sites with K d values of 0.40 ± 0.06 nM and 0.36 ± 0.08 nM for m5F and 14B, respectively, with a corresponding number of binding sites ( B max ) of 163 ± 20 and 254 ± 51 fmol/mg protein was observed. The rank order of potency in inhibiting [ 125I]VIP binding was in both cell lines: VIP > helodermin > pituitary adenylate cyclase activating polypeptide 1–27 (PACAP27) > peptide histidine isoleucine (PHI) > secretin. VIP caused a dose-dependent increase in cAMP-formation in both m5F and 14B cell membranes with EC 50 values of 3.0 and 3.5 nM, respectively, but VIP (1·10 −9–3·10 −6 M) had no effect on insulin secretion (over 2 h) from the m5F cells. Thus, the data suggest that the VIP-receptors in these neoplastic rat cell lines, despite an apparent coupling to adenylate cyclase activity, seem to be functionally uncoupled to an effect on insulin secretion following an acute exposure to VIP.

Binding sites for pituitary adenyloate cyclase activating polypeptide (PACAP): comparison with vasoactive intestinal polypeptide (VIP) binding site localization in rat brain sections

Pituitary adenylate cyclase activating polypeptide (PACAP) is structurally similar to vasoactive intestinal polypeptide (VIP). We investigated the characteristics and topographical distribution of [ 125I]PACAP binding sites, compared with those of [ 125I]VIP binding sites in the rat brain. Radiolabeled PACAP and VIP showed highly specific binding to sections at the level of the dorsal hippocampus. The specific binding of [ 125I]PACAP was 10 times higher than that of [ 125I]VIP in hippocampal sections. [ 125I]PACAP binding was scarcely displaced by unlabeled VIP, while [ 125I]VIP binding was effectively displaced by unlabeled PACAP. Therefore, PACAP binding sites may reflect both PACAP specific binding sites and VIP/PACAP binding sites. However, the amount of VIP/PACAP binding sites was negligibly low. Autoradiography revealed that [ 125I]PACAP binding sites were dense in the piriform cortex, diagonal band, accumbens nucleus, anterior part of the striatum, hippocampal formation, habenular nucleus, lateral hypothalamic area, superior colliculus and dorsal raphe nucleus. Moderate to high labeling was observed in the medial septal nucleus, olfactory tubercle, caudal part of the striatum, most parts of the thalamus, supraoptic and periventricular hypothalamic nuclei, central gray, substantia nigra pars compacta, locus coeruleus, pontine reticular nucleus and cerebellum. Distribution pattern was remarkably different from that of [ 125I]VIP binding sites in the hippocampal formation, lateral hypothalamic area, substantia nigra pars compacta, pontine reticular nucleus and cerebellum. The present results suggest that PACAP may have a physiological role in the regulation of the central nervous system.

Investigation of the interaction of VIP binding sites with VIP and PACAP in human brain

We have compared the binding of [ 125I]vasoactive intestinal polypeptide (VIP) to human brain membranes with that of [ 125I]PACAP27. [ 125I]VIP was displaced by PACAP27, VIP and two synthetic peptides, peptide-1 (N-terminal PACAP27/C-terminal VIP) and peptide-2 (N-terminal VIP/C-terminal PACAP27), but the IC 50 of PACAP27 and peptide-1 were 10–20 times lower than those of VIP and peptide-2, [ 125I]PACAP27 was readily displaced by PACAP27 and peptide-1, with an IC 50 of less than 1 nM, but poorly by VIP and peptide-2. Chemical cross-linking revealed that both labels were bound to polypetides of M r 66,000 and M r 50,000. The results indicate that in human brain membranes both binding sites have a higher affinity to the N-terminal sequence of PACAP27, and VIP binding sites prefer PACAP27 to VIP itself.

125I]Vasoactive intestinal polypeptide binding sites: Quantitative autoradiographic distribution in the rat spinal cord

The quantitative autoradiographic distribution of [ 125I]vasoactive intestinal polypeptide (VIP) receptor binding sites was in vestigated in the rat spinal cord. [ 125I]VIP binding sites are discretely distributed, with a rostro-caudal gradient, along the longitudinal length of the cord; highest densities of sites being observed in its lumbar and sacral segments. In transverse sections, highest levels of [ 125I]VIP sites are present in laminae I and II, around the central canal, and in the parasympathetic lateral horn of the sacral segment. Moderate densities are seen along the medial border of the dorsal horn and the sympathetic lateral horn of the thoracic cord. Low amounts of labeling are observed in most structures of the ventral horn while white matter areas are apparently devoid of specific [ 125I]VIP binding. Thus, the distribution of spinal [ 125I]VIP receptor sites correlates well with that of VIP-like immunoreactive materials and support possible roles for this peptide in sensory neurotransmission and in the control of autonomic functions.

Vasoactive intestinal polypeptide receptors in rat cerebral vessels: an autoradiographic study.

1. Localization and pharmacological properties of the vasoactive intestinal polypeptide (VIP) receptors in rat circle of Willis arteries and in the arteries of pial-arachnoid membrane were studied using light microscope autoradiography combined with radioreceptor binding techniques. 2. [125I]-VIP was specifically bound to sections of rat cerebral arteries with a dissociation constant value of 0.5 nM and a binding site density of 80 fmol mg protein-1. Radioreceptor binding experiments revealed that the binding characteristics of [125I]-VIP were consistent with the labelling of specific VIP receptors. The rank order of potency of various substances tested to inhibit [125I]-VIP binding was the following: VIP greater than peptide histidine methionine greater than secretin greater than glucagon. 3. Light microscope autoradiography revealed the localization of [125I]-VIP binding sites in the medial layer of circle of Willis and pial arteries. Quantitative determination of [125I]-VIP binding site density in the different circle of Willis arteries demonstrated a higher accumulation of silver grains in the anterior than in the posterior cerebral arteries. Pial arteries are richer in VIP receptor sites than circle of Willis arteries. 4. These results suggest that the physiological neurogenic vasodilation elicited by VIP on cerebral arteries is mediated by the interaction with specific receptor sites located primarily within cerebral vessels structures involved in the control of cerebrovascular resistances.

Epithelial cells purified from choroid plexus have receptors for vasoactive intestinal polypeptide

Using the choroid plexus from pig a method has been developed to purify the epithelial cells from the underlying vascularized connective tissue stroma. An epithelial cell fraction was obtained that showed a purity of at least 95%, as determined by light microscopic analysis. The epithelial cells were investigated for the presence of binding sites for the neurotransmitter peptide, vasoactive intestinal polypeptide (VIP). Suspensions of epithelial cells were found to have high affinity binding sites for 125I-labelled VIP, with maximum binding obtained after 30 min incubation at 20 °C with a concentration of 50 μg cell protein per sample. Competition experiments with displacement of [ 125I]VIP binding by increasing concentrations of unlabeled VIP indicated the presence of a single class of binding sites with aK d of 3 nM and a binding capacity of 970 pmol/g cell protein. Cross-linking of [ 125I]VIP to epithelial cells with disuccinimido dithiobis (propionate) (DSP), followed by SDS-polyacrylamide gel electrophoresis, demonstrated binding to a single 55 kD protein. The receptor was highly specific for VIP as binding was only inhibited in the presence of high concentrations of the related peptides helodermin, growth hormone-releasing factor, secretin, and peptide histidine isoleucine. This is the first demonstration of VIP-binding to choroid plexus epithelial cells.

Autoradiographic localization of vasoactive intestinal polypeptide receptors in the rat mesenteric vascular tree

By the use of combined in vitro radioreceptor binding and autoradiographic techniques, we analyzed the pharmacological properties and the anatomical localization of the vasoactive intestinal polypeptide (VIP) receptor in rat superior mesenteric artery and in medium and small mesenteric artery branches. 125I-VIP was bound by sections of rat superior mesenteric artery in a manner consistent with the labeling of specific VIP receptors, with K d and B max values of 0.23 nM and 0.71 pmol/mg protein respectively. Inhibition of 125I-VIP binding with VIP and related peptides gives the following rank order of potency: VIP > peptide histidine methionine > secretin. Light microscope autoradiography reveals specific VIP binding sites within the medial layer of superior mesenteric artery and its branches. Medium and small sized vessels are richer in 125I-VIP binding sites than the larger ones.

Vasoactive intestinal polypeptide receptor binding sites in the human gastrointestinal tract: Localization by autoradiography

Vasoactive intestinal polypeptide (VIP) is a putative neurotransmitter in both the brain and peripheral tissues. To define possible target tissues of VIP we have used quantitative receptor autoradiography to localize and quantify the distribution of [ 125I]VIP receptor binding sites in histologically normal human surgical specimens. While the distribution of VIP binding sites was different for each gastrointestinal segment examined, specific vasoactive intestinal polypeptide binding sites were localized to the mucosa, the muscularis mucosa, the smooth muscle of submucosal arterioles, the circular and longitudinal smooth muscle of the muscularis externa, the myenteric plexus, and lymph nodules. In most segments, the mucosal layer expressed the highest concentration of VIP binding sites, with the duodenal and jejunal mucosa showing the highest density of receptors. These results identify putative VIP target tissues in the human gastrointestinal tract. In correlation with physiological data, VIP binding sites appear to be involved in the regulation of a variety of gastrointestinal functions including mucosal ion transport, gastric secretion, hemodynamic regulation, gastric and intestinal motility, neuronal excitability, and modulation of the immune system.

Distribution of vasoactive intestinal polypeptide binding sites in guinea pig genital tissues

Vasoactive intestinal polypeptide (VIP) binding sites were localised in sections of guinea pig genital tissues using [ 125I]VIP and quantitative in vitro receptor autoradiography. A moderate density of binding was demonstrated in the epithelium of the prostate gland, seminal vesicles and in the testes. Moderate to high VIP binding also occurred in the epithelial lining of the oviduct, uterine glands, cervix and vagina. The binding sites appear to have a dissociation constant ( K d) of 0.36 nM and maximum receptor density ( B max) of 60.5 × 10 −3 fmol/mm 2 in sections of the uterine horn. The results indicate that VIP may have a role in the secretory functions of the guinea pig genital tract.

Binding of vasoactive intestinal polypeptide (VIP) by human blood monocytes: demonstration of specific binding sites

Vasoactive intestinal polypeptide (VIP) interaction with a 94% pure preparation of monocytes isolated from human peripheral blood was studied by direct binding technique using 3-[ 125I]tyrosyl-VIP as a tracer ligand. Scatchard analysis of binding data was compatible with two classes of binding sites, one with K d = 0.25 nM and maximal binding capacity of 16 fmol/10 6 cells, and another one with K d = 25 nM and maximal binding capacity of 180 fmol/10 6 cells. The binding was time-, temperature-, and pH-dependent and was saturable, reversible, and specific. This study has demonstrated that human monocytes have high affinity/low capacity as well as low affinity/high capacity binding sites for VIP. No specific VIP binding was found in pure preparations of human granulocytes, platelets or erythrocytes.

Development of binding sites for vasoactive intestinal polypeptide in mouse cerebral cortex and cultured cortical neurons

Binding sites for vasoactive intestinal polypeptide (VIP) and the content of immunoreactive VIP were measured in the foetal and neonatal mouse brain cortex and primary cultures of foetal murine brain-cortical neurons and astrocytes. The amount of cortical VIP binding sites and the concentration of immunoreactive VIP were low before birth, but increased postnatally reaching adult level at about 3 weeks of age. In cultures, a similar rise in neuronal binding sites occurred after 10 days, whereas the VIP concentration remained lower than in adult brain cortex. No binding sites or immunoreactive VIP could be detected in cultured astrocytes. The VIP binding sites were heterogeneous both in developing brain cortex and cultured neurons, and consisted of two classes of binding sites. The high affinity constants (2.5–2.9 nM) as well as low affinity constants (50–76 nM) were unchanged during the development, whereas the number of binding sites increased. In cultured neurons the binding constants were similar to those found in the adult mouse brain cortex. The peptide specificity for the VIP binding was similar in brain cortex and neuronal culture. In conclusion, the maturation of murine brain cortical neurons is accompanied by the development of synaptosomal VIP receptors in support of the neurotransmitter function of VIP.

Chaeacterisation and distribution of vasoactive intestinal polypeptide binding sites in human brain

The binding of 125I-vasoactive intestinal polypeptide (VIP) to human brain membranes has been studied. The binding was saturable with a dissociation constant (KD) of 4.4 ± 2.0 nM and maximum binding value (Bmax) of 8.6 ± 6.2 fmoles mg tissue (mean ± SD, n = 4), and was displaced by unlabelled VIP with an IC 50 of 4 nM; secretin was much less potent with an IC 50 of approximately 8 μM. The regional distribution of 125I-VIP binding in human brain revealed highest binding values to be in frontal and temporal cortices with intermediate values in amygdala, caudate and cerebellum, with lowest values in hippocampus, substantia nigra and hypothalamus.