Pituitary adenylate cyclase-activating polypeptide (PACAP), a novel peptide of the secretin/glucagon/vasoactive intestinal polypeptide superfamily, has been initially characterized in mammals in 1989 and, only 2 years later, its counterpart has been isolated in amphibians. A number of studies conducted in the frog Rana ridibunda have demonstrated that PACAP is widely distributed in the central nervous system (particularly in the hypothalamus and the median eminence) and in peripheral organs including the adrenal gland. The cDNAs encoding the PACAP precursor and 3 types of PACAP receptors have been cloned in amphibians and their distribution has been determined by in situ hybridization histochemistry. Ontogenetic studies have revealed that PACAP is expresssed early in the brain of tadpoles, soon after hatching. In the frog Rana ridibunda, PACAP exerts a large array of biological effects in the brain, pituitary, adrenal gland, and ovary, suggesting that, in amphibians as in mammals, PACAP may act as neurotrophic factor, a neurotransmitter and a neurohormone. (C) 2001 Wiley-Liss, Inc.

Annals of the New York Academy of SciencesVolume 865, Issue 1 p. 475-477 Localization of Pituitary Adenylate Cyclase-Activating Polypeptide in the Central Nervous System of the European Eel Anguilla anguilla: Stimulatory Effect of PACAP on GH Secretiona M. MONTERO, M. MONTERO European Institute for Peptide Research (IFRMP 23), Laboratory of Cellular and Molecular Neuroendocrinology, INSERM U413, UA CNRS, University of Rouen, 76821 Mont-Saint-Aignan, FranceSearch for more papers by this authorL. YON, L. YON European Institute for Peptide Research (IFRMP 23), Laboratory of Cellular and Molecular Neuroendocrinology, INSERM U413, UA CNRS, University of Rouen, 76821 Mont-Saint-Aignan, FranceSearch for more papers by this authorK. ROUSSEAU, K. ROUSSEAU Laboratory of General and Comparative Physiology, CNRS UA 90, National Museum of Natural History, 75005 Paris, FranceSearch for more papers by this authorA. ARIMURA, A. ARIMURA US- Japan Biomedical Research Laboratories, Tulane University, Hebert Center, Belle Chasse, Louisiana 70037, USASearch for more papers by this authorA. FOURNIER, A. FOURNIER Institut National de Recherche Scientifique Santé, University of Québec, Pointe-Claire, Québec, Canada H9R 1G6.Search for more papers by this authorS. DUFOUR, S. DUFOUR Laboratory of General and Comparative Physiology, CNRS UA 90, National Museum of Natural History, 75005 Paris, FranceSearch for more papers by this authorH. VAUDRY, Corresponding Author H. VAUDRY European Institute for Peptide Research (IFRMP 23), Laboratory of Cellular and Molecular Neuroendocrinology, INSERM U413, UA CNRS, University of Rouen, 76821 Mont-Saint-Aignan, France Corresponding author: Tel.: (33) 235.14.66.24; Fax: (33) 235.14.69.46; E-mail: hubert.vaudry@univ-rouen.frSearch for more papers by this author M. MONTERO, M. MONTERO European Institute for Peptide Research (IFRMP 23), Laboratory of Cellular and Molecular Neuroendocrinology, INSERM U413, UA CNRS, University of Rouen, 76821 Mont-Saint-Aignan, FranceSearch for more papers by this authorL. YON, L. YON European Institute for Peptide Research (IFRMP 23), Laboratory of Cellular and Molecular Neuroendocrinology, INSERM U413, UA CNRS, University of Rouen, 76821 Mont-Saint-Aignan, FranceSearch for more papers by this authorK. ROUSSEAU, K. ROUSSEAU Laboratory of General and Comparative Physiology, CNRS UA 90, National Museum of Natural History, 75005 Paris, FranceSearch for more papers by this authorA. ARIMURA, A. ARIMURA US- Japan Biomedical Research Laboratories, Tulane University, Hebert Center, Belle Chasse, Louisiana 70037, USASearch for more papers by this authorA. FOURNIER, A. FOURNIER Institut National de Recherche Scientifique Santé, University of Québec, Pointe-Claire, Québec, Canada H9R 1G6.Search for more papers by this authorS. DUFOUR, S. DUFOUR Laboratory of General and Comparative Physiology, CNRS UA 90, National Museum of Natural History, 75005 Paris, FranceSearch for more papers by this authorH. VAUDRY, Corresponding Author H. VAUDRY European Institute for Peptide Research (IFRMP 23), Laboratory of Cellular and Molecular Neuroendocrinology, INSERM U413, UA CNRS, University of Rouen, 76821 Mont-Saint-Aignan, France Corresponding author: Tel.: (33) 235.14.66.24; Fax: (33) 235.14.69.46; E-mail: hubert.vaudry@univ-rouen.frSearch for more papers by this author First published: 07 February 2006 https://doi.org/10.1111/j.1749-6632.1998.tb11219.xCitations: 4 a This work was supported by INSERM (U 413), CNRS (UA 90), the Conseil Supérieur de la Pêche, and the Conseil Régional de Haute-Normandie. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume865, Issue1VIP, PACAP, AND RELATED PEPTIDES: THIRD INTERNATIONAL SYMPOSIUMDecember 1998Pages 475-477 RelatedInformation

In a previous report, we have shown that frog pituitary adenylate cyclase-activating polypeptide (fPACAP38) is a potent stimulator of corticosteroid secretion by frog adrenal slices in vitro. The aim of the present study was to determine the mode of action of PACAP on the frog adrenal gland. Immunoelectron microscopic labeling revealed that PACAP-like immunoreactivity is present in electron-dense vesicles within nerve endings located in the vicinity of both adrenocortical and chromaffin cells. Exposure of dispersed adrenal cells to fPACAP38 caused stimulation of corticosteroid secretion. Labeling of cultured adrenal cells with [125I]PACAP27 revealed the existence of PACAP-binding sites on both adrenocortical and chromaffin cells. Saturation and competition experiments showed the occurrence of high affinity and selective receptors for fPACAP38 on cultured adrenal cells. fPACAP38 (10(-8)-10(-5) M) provoked a dose-dependent stimulation of cAMP production by frog adrenal slices. Microflurimetric studies demonstrated that fPACAP38 induced a substantial elevation of the intracellular calcium concentration in both adrenocortical and chromaffin cells. The present results indicate that in the frog adrenal gland, PACAP fibers innervate both adrenocortical and chromaffin cells. The data show the presence of PACAP receptors on the two cell types. PACAP exerts a direct stimulatory effect on corticosteroid-producing cells. This effect is probably mediated through stimulation of adenylyl cyclase activity and/or augmentation of intracellular Ca2+. PACAP also increases intracellular Ca2+ in chromaffin cells. These data suggest that PACAP, released locally in the adrenal gland, acts as a neuroendocrine factor, regulating the activity of adrenocortical and chromaffin cells.

Pituitary adenylate cyclase-activating polypeptide (PACAP) has recently been isolated from the frog brain and the sequence of the peptide appears to be strikingly similar to that of mammalian PACAP. In the present study, we have investigated the localization of PACAP in the frog interrenal (adrenal) gland by immunocytochemistry using antisera directed against PACAP 38 or PACAP 27. Two types of PACAP-immunoreactive fibres were observed: thick varicose fibres coursing between adrenal cells and thin processes located in the walls of blood vessels irrigating the gland. Bilateral transection of the splanchnic nerves did not affect the intensity and distribution of PACAP immunoreactivity. The mean +/- S.E.M. concentration of PACAP, measured by radioimmunoassay in crude adrenal extracts, was 0.65 +/- 0.16 nmol/g wet tissue. Two molecular forms of PACAP in the adrenal gland were characterized by reversed phase high-performance liquid chromatography combined with radioimmunoassay quantification. The elution profiles revealed the existence of two peaks exhibiting the same retention times as synthetic frog PACAP 38 (fPACAP 38) and PACAP 27, the predominant form being PACAP 38. The possible involvement of PACAP in the regulation of adrenal steroidogenesis was investigated in vitro using a perifusion system for frog adrenal slices. Graded doses of fPACAP 38 (0.1-10 mumol/l) increased the secretion of both corticosterone and aldosterone in a dose-dependent manner. Administration of repeated pulses of fPACAP 38 (1 mumol/l), at 120-min intervals, led to a reproducible stimulation of corticosteroid secretion without any tachyphylaxis. Prolonged infusion (2 h) of the peptide induced a rapid increase in corticosterone and aldosterone output, followed by a gradual decline in the secretion rate, suggesting the occurrence of a desensitization phenomenon. Synthetic porcine vasoactive intestinal peptide, which is structurally related to PACAP, was about ten times less potent than fPACAP 38 in stimulating steroidogenesis while the [Des-His1]-fPACAP 38 analogue was 100 times less effective. These results demonstrate that a peptide closely related to fPACAP 38 is present in fibres innervating the frog adrenal gland and could participate in the regulation of corticosteroid secretion, particularly during neurogenic stress.

Pituitary adenylate cyclase‐activating polypeptide (PACAP) is a 38 amino‐acid peptide which belongs to the glucagon/secretin/ vasoactive intestinal peptide superfamily. The sequence of PACAP is identical in all mammalian species studied so far but frog PACAP differs by one amino‐acid from mammalian PACAP. The aim of the present study was to investigate the presence of PACAP in the hypothalamo‐pituitary complex of the frog Rana ridibunda and to determine the biological activity of frog PACAP on homologous pituitary cells. The distribution of PACAP‐containing neurons and fibers was examined by the indirect immunofluores‐cence method using an antiserum raised against the N‐terminal region of the peptide. In the hypothalamus, PACAP‐immunoreactive perikarya were localized in the preoptic nucleus and the dorsal and ventral infundibular nuclei. Beaded nerve fibers were observed coursing from the ventral infundibular nucleus to the external vascular layer of the median eminence. A dense network of immunoreactive axons terminated in the vicinity of the capillaries of the hypophysial portal system. The neurointermediate lobe and the distal lobe of the pituitary were devoid of immunoreactive elements. The amount of PACAP‐like immunoreactive material in hypothalamus extracts was measured by radioimmunoassay; the apparent concentration of PACAP was 4.5 ng/mg protein. Synthetic frog PACAP38 and PACAP27 induced a similar dose‐dependent stimulation of cAMP production in isolated frog distal lobe pituitary fragments (ED 50 = 2 × 10 −8 M). At the maximum dose tested (5 × 10 −6 M), both frog PACAP38 and PACAP27 produced a 4‐fold increase in cAMP production. In contrast, the truncated form [Des‐His 1 frog PACAP38 did not affect adenylate cyclase activity demonstrating therefore that the N‐terminal histidyl residue is essential for the biological activity of the peptide. [Des‐His 1 ]frog PACAP38 did not antagonize the stimulatory effect of frog PACAP38 or PACAP27 on cAMP production. Taken together, these data support the concept that, in amphibians as in mammals, PACAP may act as a hypophysiotropic neuropeptide.

Significant CRF activity was found in a fraction with Rf = 0.82-0.7 or VE/VT = 0.41-0.48 obtained by gel filtration of acid extracts of pig hypothalami on Sephadex G-25. The activity of this fraction decreased markedly during subsequent purification, particularly in the last two steps. From this fraction, a heptapeptide with significant ACTH releasing activity in vitro, was isolated in pure state, and its amino acid sequence was established as H-Phe-Ile-Tyr-His-Ser-Tyr-Lys-OH. This heptapeptide was synthesized by solid phase methods. The CRF activity of synthetic heptapeptide in vitro was low but could be potentiated by a cofactor fraction from rat hypothalamic extract.

Free (approximately 1600 daltons) somatostatin-like immunoreactivity was identified in arterial plasma of dogs that had received a test meal. Neutralization of circulating somatostatin while the dogs were consuming a fatty meal increased the plasma concentrations of triglycerides, gastrin, pancreatic polypeptide, and insulin after the meal. It is concluded that, in the dog, somatostatin is a true hormone that regulates the movement of nutrients from the gut to the internal environment.

The effects of antisomatostatin serum upon the levels of growth hormone, glucagon-like immunoreactivity (GLI), glucagon, insulin and post-prandial triglyceride levels were examined in a group of 5 dogs before and after a fat-rich meal. Within 1 min after the injection of sheep antisomatostatin, plasma growth hormone and GLI levels increased significantly above baseline levels before the meal and remained elevated for 45 to 60 min after the meal, whereas the administration of nonimmune sheep serum to the same dogs did not cause significant changes in either hormone. Plasma insulin, glucagon and triglyceride levels after antisomatostatin serum were not significantly different from the controls. These findings suggest that endogenous somatostatin influences the secretion of growth hormone and GLI via a pathway readily accessible to intravenously injected antibodies, probably via the circulation, whereas any influence that somatostatin may have upon the secretion of insulin and glucagon must take place via a pathway inaccessible to intravenously administered antisomatostatin serum, i.e. within the islets themselves.

The effects of the instillation of glucose, fat, casein hydrolysate, and HCl into the gastrointestinal tract upon plasma levels of somatostatin-like immunoreactivity (SLI) in the venous effluent of the pancreas, fundus and antrum of the stomach, and in the inferior vena cava (IVC) were determined in normal laparotomized dogs. Fasting SLI levels in the effluent plasma from these sites were significantly greater than IVC levels. The intragastric administration of glucose elicited a prompt and significant rise in SLI levels in pancreatic, fundic and antral venous plasma, and in IVC plasma; intraduodenal glucose elicited smaller increments. After intragastric fat, a smaller, more gradual increase in the pancreatic and fundic effluents was observed, whereas the rise in antral SLI was minute, and IVC SLI did not rise significantly. Intraduodenal fat elicited a prompt increase in the pancreatic and antral vein SLI levels, and a small but significant increase in fundic and IVC plasma which suggests faster release of enteric factors that influence SLI secretion in the pancreas and antrum. Intragastric casein hydrolysate elicited a prompt increase in SLI in both the pancreatic and fundic veins, the latter being marked, but the antral SLI response was small; IVC SLI rose significantly within 15 min. Intragastric HCl provoked a prompt and marked rise in pancreaticoduodenal and antral vein SLI but no increase in fundic vein SLI; IVC SLI levels rose significantly within 20 min. Intraduodenal HCl elicited an even more prompt and marked pancreatic SLI response, and SLI rose significantly in both the fundic and antral venous effluents; IVC SLI also rose more promptly. In dogs with a gastric fistula that prevented intraduodenal entry of HCl, intragastric HCl elicited only a very small and transient rise in pancreaticoduodenal vein SLI, markedly stimulated the antral SLI response, but completely suppressed fundic venous SLI levels. The results indicate that all three nutrients stimulate SLI release from the pancreas and stomach. The greater SLI response to intragastric, as opposed to intraduodenal, glucose suggests that unidentified local factors are of importance. The responses to the intraduodenal instillation of HCl and fat suggest a role of enteric hormones in the release of SLI from the pancreas and fundus and antrum of the stomach. Additionally, there is evidence of direct effects of HCl upon gastric SLI release.

An animal model for testing the in vivo potency of somatostatin analogs in inhibiting the release of insulin and glucagon is described. The secretion of these pancreatic hormones was stimulated in rat by infusion of arginine. The plasma insulin level increased almost to a maximum after an infusion of 10 min, while plasma glucagon rose more slowly, reaching its maximum only after a 30 min infusion. Concomitant infusion of graded doses of somatostatin (2.5, 10, 40 and 160 microgram/100 g BW) for 30 min inhibited both insulin and glucagon release in a dose-dependent manner, enabling us to test somatostatin analogs for insulin and glucagon-suppressive activity in a semi-quantitative manner. Using this animal model, 3 analogs of somatostatin [D-Cys14]-, [Ala2, D-Cys14]- and [D-Trp8, D-Cys14]somatostatin were tested in a 4-point assay. They all showed dissociated activity in inhibiting the secretion of glucagon more than that of insulin.

There is now good evidence that the secretion of LH and FSH from the anterior pituitary gland is controlled principally by the central nervous system and a feedback system, involving sex steroids [1, 2]. The hypothalamus stimulates the secretion of follicle stimulating hormone (FSH), luteinizing hormone (LH) and other pituitary hormones by releasing regulatory substances into portal blood flowing from the median eminence region into the pars distalis [3, 4]. Table 1 lists the known hypothalamic hormones and the new nomenclature we have proposed for them [4]. In this report we shall be concerned only with LH-releasing hormone (LH-RH) and FSH-releasing hormone (FSH-RH). Their function is to augment the secretion of LH and FSH.