Comparative Distribution of Pituitary Adenylate Cyclase-Activating Polypeptide and Vasoactive Intestinal Polypeptide Immunoreactivity in the Chicken Forebraina (original) (raw)
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Annals of the New York Academy of Sciences, 1998
Pituitary adenylate cyclase-activating polypeptide (PACAP) is a relatively new member of the secretin/glucagon/vasoactive intestinal polypeptide (VIP) family. It was identified and purified on the basis of its ability to stimulate the accumulation of cyclic adenosine monophosphate (cAMP) in rat anterior pituitary cell cultures. Originally, two forms of the peptide were isolated from the ovine hypothalamus, one of 38 amino acids (PACAP-38) and a C-terminally truncated form of 27 residues (PACAP-27). The primary structure of PACAP is highly conserved during evolution. PACAP immunoreactivity is found in high concentration in the central nervous system of mammals (sheep, rat, monkey, and human) and amphibians (frog) and in various other tissues such as testis and adrenal gland. However, in avian species little is known about PACAP. Using polyclonal rabbit and sheep antisera we investigated the distribution of PACAP-containing neurons in the forebrain of juvenile female chickens intraven-tricularly injected with colchicine.
Regulatory Peptides, 1995
Pituitary adenylate cyclase activating polypeptide (PACAP) isolated from ovine hypothalamus is considered to be a member of the vasoactive intestinal peptide/glucagon/secretin/growth hormone-releasing hormone family of peptides. Two forms of PACAP, PACAP38 and PACAP27, have been demonstrated in the rat hypothalamus. The PACAP precursor contains another peptide called PACAP-related peptide (PRP), but so far no information on this peptide in tissue exists. We have developed three radioimmunoassays specific for PACAP38, PACAP27 and PRP and demonstrate that all three preproPACAP peptides are expressed in the rat hypothalamus, the PACAP38/PACAP27 ratio being around 60 and the PACAP38/PRP ratio being around 10. HPLC analysis of hypothalamic extract showed that PACAP38 and PACAP27 are found in only one form corresponding to the respective synthetic peptides, whereas PRP eluted in two peaks, the predominant form corresponding to synthetic PRP1-29. The cellular distribution of PACAP38, PACAP27, and PRP and corresponding mRNA in the hypothalamus was determined with immunohistochemistry and in situ hybridization histochemistry. PACAP-and PRP-immunoreactive neuronal perikarya were observed in the medial parvocellular part of the paraventricular nucleus (PVN) in colchicine pretreated rats. Some cell bodies of magnocellular variety were found in the PVN. PACAP mRNA containing cells were observed in moderate numbers in the same parts of the paraventricular nucleus. PACAP-and PRP immunoreactive fibres and varicosities were distributed in the PVN and in the periventricular nucleus. These da~:a show that PACAP38, PACAP27 and PRP are expressed in the parvocellular part of the PVN, implying roles as hypothalamic regulatory peptides.
Neuropeptides, 1993
The distribution of VIP-immunoreactive neurons and fibers was detected in the hypothalamus of the chick by immunohistochemistry and light microscopy. A large amount of VIP cellular bodies was localized in the anterior and medial area of the hypothalamus with the highest density of cells in supraoptic, magnocellular preoptic, suprachiasmatic and paraventricular nuclei. Only few VIP-immunoreactive neurons were observed in the caudal section of infundibuli nucleus. A considerable concentration of VIP-positive fibers was also detected in the external layer of the anterior and posterior median eminence. Their presence might have origin both from the neurons of the infundibuli nucleus and from the cells of the paraventricular nucleus. Few VIP-immunoreactive fibers were revealed in the organum vasculosum of the lamina terminalis. These results tend to suggest that VIP may play more than one role in the hypothalamic regions, particularly in the preoptico-hypothalamic area. The presence of this peptide in the median eminence supports even more the hypothesis that it may be released into the portal circulation and transported to the pars distalis of the pituitary gland.
Brain Research, 2007
Several lines of evidence support a role for pituitary adenylate cyclase-activating polypeptide (PACAP) in the regulation of energy balance. In the present study, we have used fluorescent in situ hybridization and immunohistochemistry to investigate in detail the cellular localization and chemical content of PACAP mRNA-and peptide-containing neuronal cell bodies in the mediobasal hypothalamus of the rat. PACAP mRNA-containing cell bodies were demonstrated in high numbers in the ventromedial hypothalamic nucleus (VMH) and in lower numbers in the arcuate nucleus (Arc). In colchicine-treated rats, PACAP immunoreactivity was demonstrated in many cell bodies of the VMH and several cell bodies of the ARC. Doublelabeling revealed that PACAP immunoreactivity was present in approximately 20% of pro-opiomelanocortin (POMC) neurons in the ventrolateral Arc as shown by presence of αmelanocyte-stimulating hormone (α-MSH), but not in agouti-related peptide (AgRP)containing neurons in the ventromedial aspect of the Arc. PACAP immunoreactivity was also colocalized with the vesicular acetylcholine transporter (VAChT; a marker for cholinergic neurons) in Arc POMC neurons. Brainstem POMC neurons in the commissural part of the solitary tract nucleus were devoid of PACAP immunoreactivity. However, several VAChTpositive neurons in the dorsal motor nucleus of the vagus nerve were also PACAP immunoreactive, whereas VAChT-positive neurons of the motor nucleus of the hypoglossal nerve were PACAP-negative. The results show presence of PACAP with α-MSH in a subpopulation of hypothalamic POMC neurons and point further to the neurochemical heterogeneity of hypothalamic, but not brainstem, POMC neurons.
Journal of Chemical Neuroanatomy, 1992
Pituitary adenylate cyclase-activating polypeptide (PACAP) is an amidated 38-residue polypeptide isolated from the ovine hypothalamus. Helodermin, a 35-amino acid peptide, and helospectins, peptides of 38 and 37 amino acid residues, have been isolated from lizard venom. PACAP, helodermin and helospectins share structural features and have a similar profile of pharmacological effects: they stimulate adenylate cyclase. We studied the distribution and characteristics of PACAP-like immunoreactivity in the rat brain with immunochemical and immunohistochemical methods and compared its distribution with that of helodermin-and helospectin-like immunoreactivities. With radioimmunoassay, the highest concentrations of PACAP-Iike immunoreactivity were found in the hypothalamus and cerebellum. PACAP-immunoreactive cell bodies were located immunohistochemically in the supraoptic nucleus, paraventricular and periventricular hypothalamic nuclei, and in the central grey. PACAP-immunoreactive fibres and terminals were detected in the medial part of the central nucleus of amygdala, in the median eminence and neurohypophysis, and in the central grey. No PACAPimmunoreactive structures were observed in areas such as the cerebral cortex, hippocampus, or cerebellum. The distribution of PACAP-like immunoreactivity differed considerably from the distribution of helodermin-and helospectin-like immunoreactivities. The results of this study suggest that PACAP is a neuropeptide with a role in the regulation of endocrine functions in the hypothalamo-hypophyseal axis.
Journal of Neuroendocrinology, 1997
Although vasoactive intestinal polypeptide (VIP) is thought to be a prolactin releasing factor, in vivo studies on sheep suggest that it is inactive in this species. Recent studies, based primarily on the rat, suggest that the related pituitary adenylate cyclase-activating polypeptide (PACAP) is also a hypophysiotrophic factor but again in sheep, this peptide has no in vivo effects on hormone secretion despite being a potent activator of adenylate cyclase in vitro. This lack of response to either peptide in vivo in sheep could be due to the low concentration of peptide that reaches the pituitary gland following peripheral injection. In the present study we therefore adopted an alternative approach of evaluating in vitro effects of these peptides on GH, FSH, LH or prolactin secretion from dispersed sheep pituitary cells. In a time-course study, PACAP (1 mmol/l) increased GH concentrations in the culture medium between 1 and 4 h and again at 12 h but had no effect in the 6 and 24 h incubations. Prolactin, LH and FSH were not affected by PACAP. The response to various concentrations of PACAP (1 nmol/l-1 mmol/l) were then evaluated using a 3 h incubation. Again prolactin and LH were not affected by PACAP and there was a small increase in GH concentrations but only at high concentrations of PACAP (0.1 and 1 mmol/l; P<0.05). PACAP also stimulated FSH secretion in cells from some animals although this effect was small. The GH response to PACAP was inhibited by PACAP(6-38), a putative PACAP antagonist, but not by (N-Ac-Tyr1, D-Arg2)-GHRH(1-29)-NH 2, a GH-releasing hormone (GHRH) antagonist. The cAMP antagonist Rp-cAMPS was unable to block the GH response to PACAP suggesting that cAMP does not mediate the secretory response to this peptide. At incubation times from 1-24 h, VIP (1 mmol/l) had no effects on prolactin, LH or GH secretion and, in a further experiment based on a 3 h incubation, concentrations of VIP from 1 nmol/l-1 mmol/l were again without effect on prolactin concentrations. Interactions between PACAP and gonadotrophin releasing hormone (GnRH), GHRH and dopamine were also investigated. PACAP (1 nmol/l-1 mmol/l) did not affect the gonadotrophin or prolactin responses to GnRH or dopamine respectively. However, at a high concentration (1 mmol/l), PACAP inhibited the GH response to GHRH. In summary, these results show that PACAP causes a modest increase in FSH and GH secretion from sheep pituitary cells but only at concentrations of PACAP that are unlikely to be in the physiological range. The present study confirms that VIP is not a prolactin releasing factor in sheep.
Journal of Neuroendocrinology, 1995
Pituitary adenylate cyclase activating peptide (PACAP) is a member of the vasoactive intestinal peptide-like peptide family. It is found in the hypothalamus, where the PACAP precursor is processed to form PACAP-38, the C-terminal truncated PACAP-27 and PACAP related peptide (PRP). Both PACAPs are potent stimulators of anterior pituitary adenylate cyclase activity, but the physiologically relevant anatomical sources of PACAP and possible importance of PRP in this regard are poorly understood. Using immunocytochemistry with epitope-specific antisera, we now show that PACAPS&, PACAP27-and PRP-positive nerve fibres are all present in the rat median eminence. The major immunoreactive species present was PACAP38. Numerous PACAP38-immmunoreactive nerve fibres were observed in the internal layer and a few were present in the posterior pituitary lobe. The external layer of the median eminence contained a few PACAP-38-immunoreactive fibres and PACAP-38-positive nerve terminals were rarely seen in the perivascular portal spaces. Surprisingly, delicate PACAP-38-positive nerve fibres were identified in the anterior pituitary lobe intermingled between the pituitary cells although none of the secretory pituitary cells contained immunoreactive PACAP38, PACAP27 or PRP and preproPACAP mRNA was not detected in the gland by Northern blotting or in situ hybridization. PACAP-27-and PRP-immunoreactive nerve fibres and terminals were found in the same locations as PACAP-38 although generally in lower numbers. Specific radioimmunoassays and HPLC revealed that PACAP-38 accounts for the vast majority of the adenohypophyseal PACAP-immunoreactivity, whereas PACAP-27 and PRP were found in low to undetectable concentrations. In primary cultures of rat pituitary cells and in the clonal gonadotrope-derived aT3-1 cell line, PACAP-27 and PACAP-38 were equipotent stimulators of cAMP accumulation, whereas PRP was ineffective. We conclude that the distribution of PACAP-imrnunoreactive nerve fibres in the hypothalamus of the adult male rat is not that expected for a classic releasing factor suggesting that other sources of PACAP are relevant for stimulation of anterior pituitary cells or that the hypothalamic PACAP system is activated under specific endocrine or developmental conditions.
The Journal of Comparative Neurology, 1994
The paraventricular nucleus of the hypothalamus (PVH) is innervated by a variety of types of neuropeptide-immunoreactive fibers. The cells of origin for many of these inputs are not known. In the present study, the combined retrograde fluorescence-immunofluorescence method was used to determine the cells of origin for neurotensin-, corticotropin-releasing factor-, brain natriuretic peptide-, somatostatin-, and met-enkephalin-like immunoreactive (-ir) fibers in the PVH. After injections of the fluorescent tracer Fluorogold into the PVH, the pattern of retrograde labeling was as previously reported (Sawchenko and Swanson, 1983, J. Comp. Neurol. 218r121-144; McKellar and Loewy, 1981, Brain Res. 217r351-357). The distribution of each type of double-labeled neuron was unique. Retrogradely labeled enkephalin-ir neurons were concentrated in two locations: the ventral part of the lateral septa1 nucleus and the lateral anterior nucleus within the AHA. A small cluster of corticotropin-releasing factor-ir neurons in the ventral lateral subnucleus of the bed nucleus of the stria terminalis were retrogradely labeled. Notable concentrations of somatostatin-ir double-labeled neurons were found in the ventral part of the lateral hypothalamic area and the medial part of the arcuate hypothalamic nucleus. Neurotensin-ir double-labeled neurons were most numerous in the anteroventral periventricular nucleus and in the retrochiasmatic area. Many brain natiuretic peptide-ir neurons in the tuberomammillary nucleus of the hypothalamus and in the pedunculopontine and laterodorsal tegmental nuclei were retrogradely labeled. The specificity of these chemically defined projections helps lay the groundwork for examining the functional organization of PVH afferents.
Cell and Tissue Research, 1990
Two nuclei, termed here the medial hypothalamic nucleus and the lateral hypothalamic retinorecipient nu= cleus, are possible homologs of the mammalian suprachiasmatic nucleus. As the mammalian suprachiasmatic nucleus is characterized by a dense concentration of vasoactive intestinal peptide (VIP)-and neurophysin (NP)-immunoreactire neurons and an absence of acetylcholinesterase (ACHE) staining, we decided to examine these factors in the ring dove hypothalamus. Neither the medial hypothalamic nucleus nor the lateral hypothalamic retinorecipient nucleus contained either VIP-or NP-like immunoreactive neurons. The lateral hypothalamic retinorecipient nucleus stained darkly for ACHE. Although there was some overlap in the distribution of VIP-and NP-like immunoreactive neurons, a clustering of both types into a well defined nucleus was not observed. Therefore, an avian homolog to the mammalian suprachiasmatic nucleus must differ in its chemoarchitecture from that of mammalian species described to date.