Biomedical subjects

M A Ghatei

Publications and source records attributed to M A Ghatei.

At least 181 records · Page 10Linked to original sources

PubMed1992

Increased neuropeptide Y content in individual hypothalamic nuclei, but not neuropeptide Y mRNA, in diet-induced obesity in rats.

Neuropeptide Y (NPY) is the most powerful appetite stimulant known, and chronic administration leads to obesity. The hypothalamic content of NPY varies with nutritional status, suggesting that it is of physiological importance. We measured NPY in specific hypothalamic nuclei and NPY mRNA in the hypothalamus by Northern blotting in rats made obese by feeding a highly palatable diet compared with controls fed standard chow. In animals fed the palatable diet, NPY concentrations were increased in the paraventricular nucleus (mean +/- S.E.M.; 19.5 +/- 2.3 vs 11.1 +/- 1.1 fmol/micrograms protein, P less than 0.02), the arcuate nucleus (20.4 +/- 3.3 vs 9.3 +/- 0.6 fmol/micrograms protein, P less than 0.01), the medial preoptic area (9.1 +/- 0.9 vs 5.9 +/- 0.7 fmol/micrograms protein, P less than 0.02) and the anterior hypothalamus (2.7 +/- 0.2 vs 2.0 +/- 0.1 fmol/micrograms, P less than 0.02). Hypothalamic NPY mRNA measured by Northern blot analysis was, however, unchanged. These results suggest that the increase in NPY was due to decreased release rather than increased NPYergic activity. The findings are in accord with the neuroendocrine disturbance and increased thermogenesis observed in this model of obesity.

Animals↗

PubMed1992

Does the arteriovenous fistula in chronic haemodialysis patients stimulate endothelin-1 release?

Plasma endothelin-1 (ET-1)-like immunoreactivity was measured by radioimmune assay in predialysis plasma samples from 16 chronic haemodialysis patients (7 dialysing through arteriovenous (AV) fistulae and 9 using central venous cannulae for access), from 10 patients with functioning renal transplants (5 with AV fistulae and 5 without), and from 6 healthy subjects as controls. Among dialysis patients, ET-1 was greater in those with AV fistulae than in those using cannulae for dialysis (median (range), 5.5 (3.1) pM versus 3.7 (2.0) pM, P = 0.02), and in all haemodialysis patients ET-1 values were substantially greater than in normal controls (3.9 (3.2) pM versus 0.5 (0.1) pM; P = 0.001). In patients with functioning AV fistulae, ET-1 concentrations obtained directly from the AV anastomosis of the fistula (4.4 (3.0) pM) were less than those taken simultaneously from the contralateral arm (5.5 (3.1) pM; P = 0.04), while samples drawn from the venous side of the fistula were intermediate (4.6 (3.4) pM). In renal transplant recipients, ET-1 values did not differ significantly from those in control subjects (0.7 (1.9) pM versus 0.5 (0.1) pM, n.s.), but in these patients there was a significant difference between peripheral venous ET-1 in transplant patients with and without AV fistulae (0.8 (1.9) pM versus 0.6 (1.1) pM respectively, P = 0.04). The results suggest that the increased blood flow rate through the arterialized venous circulation in the fistula arm stimulates increased ET-1 release in these patients, and that this accounts, at least in part, for the increased ET-1 found in the patients with functioning AV fistulae.

Adult↗

PubMed1992

Pituitary adenylate cyclase activating polypeptide is a potent vasodilator in humans.

The vasodilator effect of the novel peptide pituitary adenylate cyclase activating polypeptide (PACAP) was investigated in humans. Forearm blood flow was measured in six healthy men by venous occlusion plethysmography. Infusion of PACAP into the brachial artery at 0.01, 0.1, 1, 3, and 10 pmol/min produced a dose-related increase in forearm blood flow in the cannulated arm from 2.8 +/- 0.6 to 8.6 +/- 2.4 ml/100 ml/min at the highest dose (mean +/- SEM, p less than 0.05). In a subsequent experiment, where the highest dose of PACAP was repeated after a 36 min interval, there was no tachyphylaxis of the forearm blood flow response, with the forearm blood flow increasing by 129 +/- 9% during the first infusion and 128 +/- 31% during the second infusion (N.S.). In further experiments, microvascular blood flow was measured by a laser-Doppler flow probe to compare the effects of intradermally injected PACAP, vasoactive intestinal polypeptide (VIP), and calcitonin gene-related peptide (CGRP). When injected into the skin of normal volunteers at 10(-12) to 10(-11) mol/site, each peptide caused a rapid flare lasting 2-3 min, which became erythematous after 5 min. At 10(-12) mol/site, intradermally injected PACAP and VIP caused a maximum increase in skin blood flow at 15 min of 379 +/- 96 and 307 +/- 121% (% increase above basal +/- SEM), respectively, and these responses were not significantly affected by oral aspirin (600 mg) taken 1.5 h beforehand. The vasodilation induced by PACAP at 10(-12) mol/site lasted approximately 6 h, whereas the effect of the same dose of CGRP and VIP lasted less than 2 h. These data suggest that PACAP is a potent and long-lasting vasodilator in humans.

Adult↗

PubMed1991

Production of neuromedin B and neuromedin B gene expression in human lung tumor cell lines.

Gastrin-releasing peptide (GRP), a mammalian bombesin-like peptide, has been shown to be an important autocrine growth factor for small cell lung cancer (SCLC). However, not all SCLC cell lines express the GRP gene or respond mitogenically to GRP stimulation, suggesting the existence of other autocrine pathways in this tumor. Neuromedin B (NMB), the mammalian counterpart of amphibian ranatensin, has been shown to be a mitogen for SCLC cell lines in vitro. To determine whether NMB is a potential autocrine growth factor for lung tumors, NMB gene expression, peptide synthesis, and secretion have been investigated in a panel of SCLC and non-SCLC (NSCLC) cell lines. Northern blot analysis and enzymatic amplification from mRNA by polymerase chain reaction showed that the NMB gene was expressed in all SCLC and NSCLC cell lines examined. In contrast, the GRP gene was expressed in four of six classic SCLC cell lines but not in variant SCLC or NSCLC cell lines. Immunoreactive NMB was detected by radioimmunoassay in the majority of classic SCLC, in one of three variant SCLC and in one of three NSCLC cell lines, and secreted NMB was detected in medium conditioned by a SCLC and a NSCLC cell line. The present study also demonstrated the presence of immunoreactive GRP in the absence of detectable GRP gene expression. The antiserum used in the GRP radioimmunoassay failed to cross-react with NMB but showed some cross-reactivity with amphibian phyllolitorin raising the possibility that certain SCLC cell lines may produce a phyllolitorin-like peptide.

Base Sequence↗

PubMed1991

Differential neuropeptide expression after visceral and somatic nerve injury in the cat and rat.

The expression of neuropeptides galanin, vasoactive intestinal polypeptide (VIP) and substance P was compared after injury to somatic (sciatic, pudendal) and visceral (pelvic) nerves. Studies in normal rats and the mutant rat 'mutilated foot' suggested that galanin increases in sensory but not sympathetic fibres after sciatic nerve injury, while VIP appears to increase in both sensory and sympathetic fibres, and substance P to decrease in sensory fibres. A direct comparison of neuropeptide changes after somatic and visceral nerve injury was made in the cat dorsal sacral spinal cord, where both pudenal (somatic) and pelvic (visceral) afferents terminate. Four weeks after pudendal nerve transection in the cat there was an increase of VIP and galanin but decrease of substance P in the dorsal sacral cord, similar to the changes in lumbar dorsal cord after sciatic nerve section in the rat. In contrast, 4 weeks after pelvic nerve transection in the cat, galanin was unchanged in the ipsilateral dorsal sacral spinal cord, whereas VIP is known to decrease markedly and substance P to remain unchanged. There is thus differential peptide expression before and after injury in somatic and visceral systems, which may be regulated in part by the target organ. We have proposed that the neuropeptide changes occur in neurons that regulate development, maintenance and repair after injury, processes that may differ in somatic and visceral systems.

Animals↗

PubMed1991

New autonomic and sensory neuropathy with loss of adrenergic sympathetic function and sensory neuropeptides.

A 30-year-old woman with longstanding dizziness was found to have a severe postural fall in blood pressure and a reduced skin axon-reflex flare response. Autonomic tests indicated selective impairment of adrenergic sympathetic function. Plasma noradrenaline, adrenaline, dopamine, and dopamine beta hydroxylase were undetectable. Skin biopsy specimens showed loss of tyrosine hydroxylase and neuropeptide Y (markers of adrenergic sympathetic fibres) and of substance P and calcitonin gene-related peptide (sensory neuropeptides). A sural nerve biopsy specimen showed severe depletion of unmyelinated fibres. The constellation of losses were compatible with nerve growth factor (NGF) deprivation, which was confirmed on assay. This new syndrome may be explained by loss of trophic action of NGF.

Adrenergic Fibers↗

PubMed1991

Pituitary adenylate cyclase-activating polypeptide: a novel, long-lasting, endothelium-independent vasorelaxant.

The vasoactivity of the 27- and 38-amino acid forms of the novel peptide pituitary adenylate cyclase-activating polypeptide (PACAP) was tested in vitro. Both forms of PACAP caused endothelium-independent vasodilation (assayed by their vasodilator action on rabbit aorta). When superfused for 1 min the relaxation EC50 of PACAP27 was 23 +/- 8 nM and of PACAP38 was 152 +/- 66 nM. PACAP was 100-fold more potent than vasoactive intestinal polypeptide (VIP) (PACAP27 shows 68% amino acid sequence homology with VIP), and had a prolonged duration of action, a 1 min exposure to 1 microM PACAP27 lasting 135 +/- 7 min and to 1 microM PACAP38 108 +/- 3 min. Adenylate cyclase activity in homogenates of rabbit aortic smooth muscle cells was increased by PACAP27 and PACAP38 with EC50s of 4.4 and 0.73 nM, respectively. PACAP27 and PACAP38 are potent, long-lasting, endothelium-independent vasodilators.

Adenylyl Cyclases↗

PubMed1991

Glucagonomas of transgenic mice express a wide range of general neuroendocrine markers and bioactive peptides.

Pancreatic tumours of transgenic mice carrying a glucagon-promoted simian virus 40 (SV40) T antigen oncogene have been analysed by histological, histochemical, ultrastructural and radioimmunological means. Seven transgenic mice were examined revealing dysplastic and neoplastic lesions in the endocrine pancreas. Four tumours were identified, one of which metastasized to periadrenal spaces and paravertebral lymph nodes. Benign tumours were composed of argyrophilic, endocrine cells reactive to a range of antibodies against neuroendocrine markers (neuron-specific enolase, protein gene product 9.5, chromogranin A, synaptophysin and protein 7B2) and different fragments of the proglucagon molecule (glucagon, glicentin, glucagon-like polypeptides 1 and 2). A few tumour cells expressed pancreatic polypeptide, somatostatin or insulin. Conventional ultrastructural analysis and immunogold labelling revealed typical glucagon-immunoreactive alpha granules which co-stored glicentin and glucagon-like polypeptides 1 and 2. The malignant primary tumour and its metastases were composed mainly of cells which did not show immunoreactivity for neuroendocrine markers or peptides. Atypical, glucagon-immunogold labelled granules were detected at electron microscopy in differentiated tumour cells and C-type retroviral particles in the largest tumour population of degranulated cells. The transgene-encoded oncoprotein SV40 large T-antigen was detected in the nuclei of well-differentiated tumour cells and in alpha cells of some dysplastic islets. All tumour-bearing mice showed high levels of circulating glucagon-like immunoreactivity. Transgenic mice harbouring the glucagon-promoted SV40 T antigen oncogene may provide a model for human glucagonoma.

Animals↗

PubMed1991

Reduced hypothalamic neurotensin concentrations in the genetically obese diabetic (ob/ob) mouse: possible relationship to obesity.

Hypothalamic tissue levels of nine regulatory peptides (bombesin, calcitonin gene-related peptide [CGRP], galanin, neuromedin B, neuropeptide Y [NPY], neurotensin, somatostatin, substance P, and vasoactive intestinal peptide [VIP]) were compared in Aston obese diabetic (ob/ob) and lean (+/?) mice aged 4, 16, and 28 weeks. Neurotensin concentrations were significantly lower in ob/ob mice than in lean mice, with a 20% reduction (P = .03) in the whole hypothalamus at 4 weeks of age, a 24% reduction (P = .009) in the lateral hypothalamus at 16 weeks, and a 50% reduction (P = .0007) in the central hypothalamus at 28 weeks of age. Apart from a 42% increase in vasoactive intestinal peptide concentrations in the central hypothalamus of ob/ob mice at 28 weeks (P = .02), levels of the other eight peptides examined did not differ significantly between obese and lean groups. Neurotensin is known to cause anorexia and increased energy expenditure when injected into the central hypothalamus. Reduced hypothalamic neurotensin concentrations may reflect reduced neurotensinergic activity, which might contribute to hyperphagia and decreased energy expenditure, two major defects that contribute to obesity and diabetes in the ob/ob syndrome.

Analysis of Variance↗

PubMed1991

Hypothalamic regulatory peptides in obese and lean Zucker rats.

1. Hypothalamic concentrations of nine peptides with experimental effects on energy balance were compared in obese (fa/fa) and lean (Fa/?) male Zucker rats. To determine whether any peptide differences between obese and lean rats might be due to the overweight condition per se, separate groups of obese rats were food-restricted to reduce their body weight to lean values. 2. Concentrations of neuromedin B, a bombesin-like peptide, in the central hypothalamus were significantly higher in obese than in lean rats. This difference was not affected in food-restricted obese rats. 3. Hypothalamic levels of neuropeptide Y, an extremely potent central appetite stimulant, were similar in lean and freely fed obese rats but central hypothalamic levels of neuropeptide Y rose significantly in food-restricted obese rats. 4. These findings suggest that disturbances in hypothalamic neuromedin B concentrations may be involved in the obesity syndrome of the fa/fa Zucker rat. Increased central hypothalamic levels of neuropeptide Y in food-restricted rats suggest that this peptide may help to defend body weight by stimulating eating after weight loss.

Animals↗

PubMed1991

Islet amyloid polypeptide: production by an osteoblast cell line and possible role as a paracrine regulator of osteoclast function in man.

1. The recently discovered peptide islet amyloid polypeptide shows considerable sequence homology with calcitonin-gene-related peptide, itself an alternative product of the calcitonin gene. The possibility that islet amyloid polypeptide might affect calcium homoeostasis and bone cell function was investigated. 2. Islet amyloid polypeptide messenger RNA was found to be expressed by human HTb 96 osteoblast-like cells in culture, and islet amyloid polypeptide immunoreactivity was present in the cell culture medium. 3. Infusion of islet amyloid polypeptide (150 pmol min-1 kg-1) caused a fall in serum calcium and phosphate concentrations in five patients with Paget's disease of the bone. This was similar to that caused by infusion of calcitonin (50 pmol min-1 kg-1). 4. These findings raise the possibility that islet amyloid polypeptide may act as a local factor within bone, produced by osteoblasts and regulating osteoclast function. The possibility of an action of islet amyloid polypeptide on the renal handling of calcium seems unlikely but is not totally excluded.

Aged↗

PubMed1991

Endothelin in human brain and pituitary gland: comparison with rat.

To investigate the physiological roles of endothelin (ET) in the brain and pituitary gland, the presence of immunoreactive (ir) ET and ET receptors was studied by radioimmunoassay and receptor assay in humans and rats. ir-ET concentrations in human brain (6-10 fmol/g of wet weight) were comparable with the levels in the rat brain (5-9 fmol/g of wet weight). Higher concentrations of ir-ET were found in human pituitary glands (147 +/- 30 fmol/g of wet weight, mean +/- SEM) and rat posterior pituitary lobes (88 +/- 26 fmol/g of wet weight). Fast protein liquid chromatography (FPLC) showed that the ir-ET in human hypothalamus and brainstem was mainly ET-1, while the ir-ET in human pituitary was mainly ET-3. FPLC of the whole rat brain extract showed a larger peak in the position of ET-3 and a smaller peak in the position of ET-1. Receptor assay showed that [125I]ET-1 binding sites were present in very large numbers in all five human brain regions and four rat brain regions examined but were much less abundant in the human pituitary. ET mRNA was detected by Northern blot hybridization in human pituitary but not in human hypothalamus. These findings are in accord with the possibility that ET acts as a neurotransmitter, neuromodulator, or neurohormone.

Animals↗

PubMed1991

Immunoreactive endothelin in human plasma, urine, milk, and saliva.

Using a highly sensitive radioimmunoassay, elevated plasma immunoreactive endothelin (ir-ET) levels were found in patients with diabetes mellitus (1.88 +/- 0.12 pmol/L, mean +/- SEM, n = 100), patients undergoing maintenance hemodialysis (4.28 +/- 0.76 pmol/L, n = 14), patients with acute myocardial infarction (3.43 +/- 1.03 pmol/L, n = 6), and patients with subarachnoid hemorrhage (4.92 +/- 0.64 pmol/L, n = 14) (normal controls: 0.54 +/- 0.05 pmol/L, n = 19). ir-ET was also present in urine (2.1 +/- 0.3 pmol/L, n = 12), breast milk (6.8 +/- 1.6 pmol/L, n = 16), and saliva (2.0 +/- 0.2 pmol/L, n = 15) obtained from healthy subjects. Chromatography studies verify the identity of endothelin. Fast protein liquid chromatography (FPLC) showed one peak in the normal plasma extract, three peaks in the plasma extracts from diabetic patients and patients undergoing maintenance hemodialysis, three peaks in the urine extract, four peaks in the milk extract, and five peaks in the saliva extract. When the materials eluting in the void volume on FPLC of urine and saliva extracts were loaded onto a Sephadex G-25 column, the ir-ET was eluted in a higher molecular weight region. Incubation of endothelin-1, endothelin-2, and endothelin-3 in urine for 5 h showed that the total amount of ir-ET decreased to less than 30% of the initial levels, suggesting that endothelins are very unstable in urine.

Adult↗

PubMed1991

Glucagon 1-21 reduces intestinal epithelial cell proliferation in parenterally fed rats.

The hypothesis that glucagon 1-21 (G1-21) is trophic to the gastrointestinal tract was investigated in the hypoplastic intestine of intravenously maintained rats. Three groups of eight rats were fed parenterally for three days and then were infused with either 0, 20 or 80 micrograms rat-1 day-1 of G1-21 for 3 days. No significant effect on the weight of the stomach, caecum or colon was observed, but both the weight and crypt cell production rate of the small intestine were significantly decreased by G1-21. Plasma enteroglucagon was also decreased by G1-21 treatment. It is concluded that G1-21 does not have a trophic effect on the gastrointestinal tract, and, in fact, has an antiproliferative effect on the small intestine, which could in turn be modulated by decreased levels of endogenous enteroglucagon.

Animals↗

PubMed1991

Developmental patterns of glucagon-like peptide-1-(7-36) amide and peptide-YY in rat pancreas and gut.

Glucagon-like peptide-(17-36) amide [GLP-1-(7-36) amide] and peptide tyrosine tyrosine (PYY) are both products of the enteroglucagon cell. To examine the changes occurring during development, we analyzed by RIA the pancreatic concentrations of these two peptides in fetal and neonatal rats. The levels obtained were compared with those of the classical islet hormones, insulin, somatostatin, and glucagon. The total hormone content of the pancreas increased with age for insulin, glucagon, and somatostatin. The amounts of GLP-1-(7-36) amide immunoreactivity (IR) and PYY, however, remained approximately constant in the 3-, 8-, and 30-day-old and adult pancreas. GLP-1-(7-36) amide IR showed only a single peak by gel chromatography, but further analysis by anion exchange chromatography showed that during the fetal period (-18 days) and 3 days postpartum GLP-1-(7-36) amide was the main product, whereas 30 days postpartum and in adult pancreas mainly GLP-1 and an intermediate form were found. Similar analyses of gut extracts revealed that only GLP-1-(7-36) amide is produced during intestinal development. The gut content of GLP-1-(7-36) amide IR and PYY IR increased approximately 100 times between the fetus and the 30-day-old rat. This study reveals a complex and specific regulation of posttranslational processing during maturation for these two peptides.

Aging↗

PubMed1991

Peptide contents of neuropeptide Y, vasoactive intestinal polypeptide, and beta-calcitonin gene-related peptide and their messenger ribonucleic acids after dexamethasone treatment in the isolated rat islets of Langerhans.

A number of neuropeptides including neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), and beta-calcitonin gene related peptide (beta-CGRP) are known to influence insulin secretion. In order to investigate whether they might have a local autocrine/paracrine effect within the islets of Langerhans we screened isolated islets by Northern blot analysis and RIA for a number of peptides and found evidence for the presence of messenger RNA (mRNA) encoding NPY, VIP, and beta-CGRP. Dexamethasone treatment for 12 days increased the content of NPY, VIP, and beta-CGRP significantly from 1.3 +/- 0.3 to 19.8 +/- 1.6; 0.25 +/- 0.03 to 0.91 +/- 0.1; 2.2 +/- 0.2 to 4.8 +/- 0.1 fmol/islet respectively, mean +/- SEM (n = 4, P less than 0.05) and remained elevated 24 h after recovery. However when the results were normalized and expressed as a ratio of insulin content only NPY and VIP were significantly raised. Five days post treatment VIP was still significantly elevated compared to controls. mRNA for NPY increased 10-fold and for VIP increased 2 1/2 times after dexamethasone whereas mRNA for beta-CGRP was not significantly different from controls. Neither capsaicin nor 6-hydroxydopamine affected islet content or message of NPY, VIP, and beta-CGRP. Immunoreactive NPY and its mRNA were detected in two cultured beta-cell lines, HIT T-15 and RIN m5F cells whereas VIP and beta-CGRP were undetectable. The local islet synthesis of neuropeptides, which are known to influence islet hormone release pharmacologically, suggests the possibility that they may play a role in intraislet paracrine regulation.

Animals↗

PubMed1991

Endothelin in human brain and pituitary gland: presence of immunoreactive endothelin, endothelin messenger ribonucleic acid, and endothelin receptors.

The presence of immunoreactive (IR) endothelin, endothelin mRNA, and endothelin receptors in human brain and pituitary gland has been studied by RIA, Northern blot hybridization, and receptor assay. IR endothelin was detected in all five brain regions examined (cerebral cortex, cerebellum, brain stem, basal ganglia, and hypothalamus) (6-10 fmol/g wet wt) and spinal cord (22 +/- 6 fmol/g wet wt, n = 7, mean +/- SEM). Higher concentrations of IR endothelin were found in the pituitary gland (147 +/- 30 fmol/g wet wt). Fast protein liquid chromatographic analysis of the IR endothelin in pituitary gland showed a large IR peak in the position of endothelin-3 and a smaller peak in the position of endothelin-1, whereas IR endothelin in the hypothalamus and brain stem was mainly endothelin-1. Endothelin messenger RNA was detected by Northern blot hybridization in the pituitary but not in hypothalamus. The receptor assay showed that 125I-endothelin-1 binding sites were present in large numbers in all five brain regions but were much less abundant in the pituitary gland. Binding capacity and dissociation constant were 5052 +/- 740 fmol/mg protein and 0.045 +/- 0.007 nM in brain stem and 963 +/- 181 fmol/mg protein and 0.034 +/- 0.009 nM in hypothalamus. In the pituitary gland, there were two classes of binding sites for endothelin with dissociation constants of 0.059 +/- 0.002 nM (binding capacity = 418 +/- 63 fmol/mg protein) and 0.652 +/- 0.103 nM (binding capacity = 1717 +/- 200 fmol/mg protein). Endothelin-1, -2 and -3 were almost equipotent in displacing the binding (IC50 approximately 0.04 nM). These findings are in accord with the possibility that endothelin acts as a neurotransmitter, neuromodulator or neurohormone in man.

Aged↗

PubMed1991

Investigation and characterization of receptors for pituitary adenylate cyclase-activating polypeptide in human brain by radioligand binding and chemical cross-linking.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a novel peptide of hypothalamic origin which increases adenylate cyclase activity in rat anterior pituitary cell cultures. The 38-amino acid peptide shows a close sequence homology to vasoactive intestinal peptide (VIP). Binding sites for PACAP in membranes from postmortem human brain tissue were studied using [125I]PACAP27 as the radioligand. High specific binding sites (amount of specific binding measured at 0.25 nM [125I]PACAP27 in femtomoles per mg protein +/- SEM; n = 4) were present in hypothalamus (344.5 +/- 13.0), brain stem (343.0 +/- 29.3), cerebellum (292.0 +/- 21.1), cortex (259.6 +/- 19.8), and basal ganglia (259.2 +/- 50.3). Specific binding sites in pituitary, although present, were less abundant (35.0 +/- 8.9). Binding of [125I]PACAP27 was reversible and time, pH, and temperature dependent. Despite the homology with VIP, VIP was a poor inhibitor of [125I]PACAP27 binding (IC50, greater than 1 microM) compared with PACAP27 (IC50, 0.5-1.3 nM) and PACAP38 (IC50, 0.2-1.3 nM). Scatchard plots of [125I]PACAP27 binding showed the presence of both high and lower affinity sites. Chemical cross-linking of PACAP-binding sites revealed that [125I]PACAP27 was bound to polypeptide chains of 67,000 and 48,000 mol wt. Thus, we have demonstrated the presence of PACAP-specific receptors in human brain which are not VIP receptors. This opens the possibility of PACAP functioning as a novel neurotransmitter/neuromodulator in human brain.

Brain↗