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The presence of PACAP was revealed in the anterior pituitary with RIA, HPLC, and with the demonstration of its mRNA. The level of PACAP mRNA in the anterior pituitary is the highest during the proestrous LH surge. In our immunohistochemical studies we were able to demonstrate PACAP immunoreactive cells in the anterior pituitary. The shape and the distribution of PACAP immunoreactive cells were very similar to that of the gonadotropes; however, the number of PACAP cells was less than that of LH cells. Additionally, another PACAP-positive cell population with small diameter appeared in the proestrous stage, during pregnancy and lactation. Double labeling revealed that the major part of large PACAP cells exhibited LH immunoreactivity and those with a small diameter contained PRL. It is not clear whether the pituitary- or the hypothalamic-born PACAP, or both, influence pituitary LH and PRL secretion. I.c.v. administration of PACAP just prior to the critical period in the proestrous stage inhibited the expected ovulation and blocked the proestrus LH and PRL surge, although i.v. administration of PACAP had no effect. PACAP antiserum did not interfere with ovulation when i.c.v. or i.v. injection was used. Our results support the view that PACAP has a role in the control of LH and PRL secretion during the estrous cycle, pregnancy, and lactation. The inhibitory effect of PACAP on ovulation is mediated through the hypothalamus.

By means of a whole mount immunocytochemical approach, the distribution patterns of pituitary adenylate cyclase-activating polypeptide (PACAP)-27 and PACAP-38 were identified in the ventral nerve cord (VNC) ganglia of the earthworms Eisenia fetida and Lumbricus terrestris. Each PACAP form appears to occur in a distinct neuron population. Positions of these populations, as well as numbers and sizes of the constituting neurons do not essentially differ between the two species. The data suggest that in Lumbricid Oligochaetes, PACAP-27 and PACAP-38 neuron populations may mediate distinct physiological processes.

Activity-dependent neurotrophic protein (ADNP) was discovered as a novel response gene for VIP and has neuroprotective potential. When the VIP paralog, PACAP38 was added to mouse neuron-glia co-cultures, it induced ADNP mRNA expression in a bimodal fashion at subpico- and nanomolar concentrations with greater response at subpicomolar level. The response was attenuated by a PAC1-R antagonist at both concentrations and by a VPAC1-R antagonist at nanomolar concentration only. An IP3/PLC inhibitor attenuated the response at both concentrations of PACAP38, but a MAPK inhibitor had no effect. A PKA inhibitor suppressed the response at nanomolar concentration only. These findings suggest that ADNP expression is mediated through multiple receptors and signaling pathways that are regulated by different concentrations of PACAP.

Pituitary adenylate cyclase-activating polypeptide (PACAP) has been reported to decrease ischemic neuronal damage and increase IL-6 secretion in rats. However, the mechanisms underlying neuroprotection are still to be fully elucidated. The present study was designed to investigate the role played by PACAP and IL-6 in mediating neuroprotection after ischemia in a null mouse. Infarct volume, neurological deficits, and cytochrome c in cytoplasm were higher in PACAP +/− and PACAP −/− mice than in PACAP +/+ animals after focal ischemia, although the severity of response was ameliorated by the injection of PACAP38. A decrease in mitochondrial bcl-2 was also accentuated in PACAP +/− and PACAP −/− mice, but the decrease could be prevented by PACAP38 injection. PACAP receptor 1 (PAC1R) immunoreactivity was colocalized with IL-6 immunoreactivity in neurons, although the intensity of IL-6 immunoreactivity in PACAP +/− mice was less than that in PACAP +/+ animals. IL-6 levels increased in response to PACAP38 injection, an effect that was canceled by cotreatment with the PAC1R antagonist. However, unlike in wild-type controls, PACAP38 treatment did not reduce the infarction in IL-6 null mice. To clarify the signaling pathway associated with the activity of PACAP and IL-6, phosphorylated STAT (signal transducer and activator of transcription) 3, ERK (extracellular signal-regulated kinase), and AKT levels were examined in PACAP +/− and IL-6 null mice after ischemia. Lower levels of pSTAT3 and pERK were observed in the PACAP +/− mice, whereas a reduction in pSTAT3 was recorded in the IL-6 null mice. These results suggest that PACAP prevents neuronal cell death after ischemia via a signaling mechanism involving IL-6.

We have found previously that pituitary adenylate cyclase-activating polypeptide (PACAP) increases the number of astrocytes generated from cultured mouse neural stem cells (NSCs) via a mechanism that is independent of the cyclic AMP/protein kinase A pathway (Ohno et al., 2005). In the present study, the signaling pathway involved in the differentiation process was further investigated. PACAP-induced differentiation was inhibited by the phospholipase C inhibitor, U73122, the protein kinase C (PKC) inhibitor, chelerythrine, and the intracellular calcium chelator, BAPTA-AM, and was mimicked by phorbol 12-myristate 13-acetate (PMA), but not by 4alpha-PMA. These results suggest that the PACAP-generated signal was mediated via the PACAP receptor, PAC1 stimulated heterotrimeric G-protein, resulting in activation of phospholipase C, followed by calcium- and phospholipid-dependent protein kinase C (cPKC). To elucidate the involvement of the different isoforms of cPKC, their gene and protein expression were examined. Embryonic NSCs expressed alpha and betaII PKC, but lacked PKCgamma. When NSCs were exposed to 2 nM PACAP, protein expression levels of the betaII isoform transiently increased two-fold before differentiation, returning to basal levels by Day 4, whereas the level of PKCalpha increased linearly up to Day 6. Overexpression of PKCbetaII with adenovirus vector synergistically enhanced differentiation in the presence of 1 nM PACAP, whereas expression of the dominant-negative mutant of PKCbetaII proved inhibitory. These results indicate that the beta isoform of PKC plays a crucial role in the PACAP-induced differentiation of mouse embryonic NSCs into astrocytes.

In neuronal/glial cocultures, pituitary adenylate cyclase-activating polypeptide 38 (PACAP38) prevented neuronal death induced by gp120, lipopolysaccharide (LPS), or other toxic agents, but the dose response of the neuroprotective effect is bimodal, with a peak at a subpicomolar concentration and another peak at a subnanomolar to nanomolar concentration. Although the signaling cascade involved in neuroprotection by nanomolar concentration of the peptide has been shown to be mediated by activation of cAMP-dependent protein kinase and subsequent activation of mitogen-activated protein kinase (MAPK), the mechanism for neuroprotection by a subpicomolar level of PACAP38 remains elusive. In the present study, the signaling involved in neuroprotection by subpicomolar PACAP38 was studied in rat neuronal/glial cocultures. Addition of PACAP38 stimulated expression and activation of extracellular signal-related kinase-type MAPK with a peak response at 10-13 M; greater concentrations of the peptide induced lesser response. cAMP production also increased at subpicomolar levels of PACAP38, but the level remained unchanged at a level four to five times higher than the base level at concentrations below 10-11 M. cAMP then started increasing again dose-dependently in a range >10-11 M PACAP38. Lipopolysaccharide (LPS)-induced neuronal death, indicated by increased release of neuron-specific enolase, was suppressed by PACAP38 in a bimodal fashion. Neuroprotection by 10-12 M PACAP38 was completely abolished by a MAPK kinase-1 inhibitor, PD98059, and also partially suppressed by Rp-cAMP, a cAMP-dependent protein kinase inhibitor. Moreover, neuroprotection by a nanomolar level of PACAP38 was completely suppressed by Rp-cAMP but not affected by PD98059. We conclude that neuroprotection by subpicomolar PACAP38 is mainly mediated by the signaling pathway involving MAPK activation and partially regulated by cAMP-dependent protein kinase activation. Furthermore, PACAP38 stimulated expression of activity- dependent neuroprotective protein (ADNP), with a peak at 10-13 M. Greater doses of the peptide induced lesser response. However, 10-13 M PACAP38-stimulated expression of ADNP was not affected by PD98059. This suggests that neuroprotection by subpicomolar PACAP38 might be mediated partially by expression of ADNP, but the major events for neuroprotection by subpicomolar PACAP38 remain to be identified.

Postischemic hyperthermia occurs after the occlusion of the middle cerebral artery (MCAO) with an intraluminal filament in rats. The cause of hyperthermia is presumed to be damage to the preoptic area, which is one of the temperature-regulatory centers of the hypothalamus. In the present study, reactions of microglial cells and astrocytes in the preoptic area were examined during the first 6 h following transient MCAO. Microglial cells and astrocytes were visualized with immunohistochemistry using antibodies against the CR3 complement receptor and the glial fibrillary acidic protein, respectively. One hour after the occlusion, activated microglial cells were observed in both the medial and lateral preoptic areas ipsilaterally, and in the medial preoptic area contralateral to the infarct. Following reperfusion, the activation of microglial cells decreased in the medial preoptic area of both hemispheres, and in the lateral preoptic area there was a loss of immunoreactive microglial cells. Fragmentation of astrocytic processes was detected in the lateral preoptic area, while in the ipsilateral medial preoptic area a moderate swelling was observed. Immunohistochemistry with an antibody against interleukin-1beta (IL-1beta) revealed scattered immunoreactive cells in both the ipsilateral and the contralateral medial preoptic area 2 h after the MCAO. Our results show that microglial activation in the preoptic area coincides with postischemic hyperthermia. However, an exclusive role for IL-1beta in the generation of hyperthermia is unlikely, and other factors are probably also responsible for postischemic hyperthermia.

Atrial natriuretic peptide (ANP) is present in gastric mucosa and preferentially binds to two subtypes of natriuretic peptide receptors (NPR), NPR-A and NPR-C. The present study examines the role of endogenous ANP in regulating endocrine secretion in rat and human stomachs. NPR-A protein expression and transcripts were identified in rat antral and fundic mucosa by Western blot and RT-PCR. In superfused rat and human antral and fundic segments, ANP (0.1 pM to 0.1 μM) caused a concentration-dependent increase in somatostatin secretion. In antrum, this was accompanied by a decrease in gastrin, and in fundus, this was accompanied by a decrease in histamine secretion. Changes in gastrin and histamine secretion reflected changes in somatostatin secretion and were abolished by somatostatin antibody. The NPR-A receptor antagonist anantin 1) inhibited basal somatostatin secretion and 2) abolished the somatostatin, gastrin, and histamine responses to ANP. We conclude that endogenous ANP, acting via the NPR-A receptor, stimulates somatostatin secretion from both antrum and fundus of rat and human stomach. Stimulation of somatostatin secretion is coupled to inhibition of gastrin secretion in the antrum and inhibition of histamine secretion in the fundus.

Mammalian testicular development and the maintenance of spermatogenesis are hormone-dependent processes that are controlled by the pituitary gonadotropins and testosterone. Recent studies have demonstrated the presence of many neuropeptides and their receptors in the testis, suggesting that these peptides operate as local regulators of testicular germ cell development and function. Among these testicular neuropeptides, the peptides that belong to the pituitary adenylate cyclase-activating polypeptide (PACAP) family, particularly growth hormone-releasing hormone and secretin, appear to show some unique common features in terms of intratesticular localization and the time of expression during the spermatogenic cycle. However, their precise physiologic roles and mechanisms of action remain unknown. This review analyzes the available information on the functional interactions among the testicular cells that appear to be mediated by locally produced neuropeptides, with a special emphasis on the peptides of the PACAP family.

Atrial natriuretic peptide (ANP) as well as its receptor, NPR-A, have been identified in gastric antral mucosa, suggesting that ANP may act in a paracrine fashion to regulate gastric secretion. In the present study, we have superfused antral mucosal segments obtained from rat stomach to examine the paracrine pathways linking ANP and somatostatin secretion in this region.ANP (0.1 pM to 0.1 microM) caused a concentration-dependent increase in somatostatin secretion (EC(50), 0.3 nM). The somatostatin response to ANP was unaffected by the axonal blocker tetrodotoxin but abolished by addition of the selective NPR-A antagonist, anantin. Anantin alone inhibited somatostatin secretion by 18+/-3% (P0.005), implying that endogenous ANP, acting via the NPR-A receptor, stimulates somatostatin secretion. Somatostatin (1 pM to 1 microM) caused a concentration-dependent decrease in ANP secretion (EC(50), 0.7 nM) that was abolished by addition of the somatostatin subtype 2 receptor (sst2) antagonist, PRL2903. Neutralization of ambient somatostatin with somatostatin antibody (final dilution 1:200) increased basal ANP secretion by 70+/-8% (P001), implying that endogenous somatostatin inhibits ANP secretion. We conclude that antral ANP and somatostatin secretion are linked by paracrine feedback pathways: endogenous ANP, acting via the NPR-A receptor, stimulates somatostatin secretion, and endogenous somatostatin, acting via the sst2 receptor, inhibits ANP secretion.

PACAP exerts neuroprotective effects under various neurotoxic conditions in vitro. In vivo, it reduces brain damage after global and transient focal ischemia. The present study investigated whether PACAP has neuroprotective effects when applied before the onset of permanent ischemia. Rats were given bolus injections of PACAP38 intracerebroventricularly, and then underwent permanent middle cerebral artery occlusion. The results show that 2 microg of PACAP significantly reduced the infarct size measured 12 and 24h after the onset of ischemia. No further reduction was obtained by a 7-day pretreatment. PACAP also ameliorated certain sensorimotor deficits. Our present study provides further evidence for the neuroprotective effects of PACAP, and implies that it might be a promising preventive therapeutic agent in ameliorating ischemic brain damage.

The onset of puberty is a concerted action of many factors which leads to cyclic LHRH release in rats. It has been demonstrated that; in common with vasoactive intestinal polypeptide (VIP), pituitary adenylate cyclase activating polypeptide (PACAP) is also involved in the differentiation of the central nervous system. In our previous work, it was shown that a single PACAP injection into neonatal female rats delayed puberty. In the present work, neonatal administration of PACAP delayed the vaginal opening and decreased the weight of anterior pituitaries, the number of expelled ova at the first ovulation and the intensity of LHRH immunostaining in the septo-preoptico-infundibular system. PACAP antiserum had a reverse effect on LHRH immunoreactivity. The other studied parameters in the latter group remained unchanged compared to control rats. It was concluded that neonatal PACAP administration delayed the onset of puberty through the influence of the LHRH neuronal system.

One of the recently found functions of pituitary adenylate cyclase activating polypeptide (PACAP) is the modulation of circadian rhythms. Widespread distribution of PACAP-containing neurons and receptors has been shown in the chicken. Recently, we have demonstrated that PACAP levels oscillate in a circadian manner in the chicken brain. Daily variation in PACAP levels might be influenced by several regulatory mechanisms. Among the structures that may regulate PACAP levels, one candidate is the pineal gland. Therefore, in the present study, we investigated the effect of pinealectomy on the levels of PACAP in the chicken brain. Animals were kept under 12:12-h light–dark schedule. Pinealectomy was performed at 3 weeks of age; sham-operated animals were used as controls. The animals were sacrificed at 15 and 24 h 1 week after pinealectomy. The brainstem and diencephalon were removed, and tissue samples were processed for PACAP and cAMP radioimmunoassay (RIA). PACAP and cAMP levels showed nighttime elevations in both the sham-operated and pinealectomized animals, except for the PACAP content in the diencephalon of pinealectomized chicken. PACAP levels of pinealectomized animals were significantly higher in the diencephalon and brainstem as compared to the control animals at both time-points. Levels of cAMP correlated well with levels of PACAP. The present results provide evidence that the pineal gland has an inhibitory impact on PACAP-neurons in the chicken brainstem and diencephalon.

Corticotropin-releasing factor (CRF), sauvagine, and urotensin I are all members of the so-called CRF neuropeptide family. Urocortin (Ucn), a 40-amino-acid neuropeptide recently isolated from the rat brain, is the newest member of this family. Until now, the distribution of Ucn in the central nervous system (CNS) has been studied only in placental mammals. We used a polyclonal antiserum against rat Ucn to determine the distribution of Ucn-like immunoreactivity in the CNS of the green frog, Rana esculenta. The great majority of Ucn-immunoreactive perikarya was seen in the anterior preoptic area, ventromedial thalamic nucleus, posterior tuberculum, nucleus of the medial longitudinal fasciculus, and Edinger-Westphal nucleus. Urocortin-immunoreactive nerve cells were also observed in the motor nuclei of the trigeminal and facial nerves and in the hypoglossal nucleus. Immunoreactive fibers were found in the medial and lateral septal nuclei, bed nucleus of the stria terminalis, many of the thalamic and hypothalamic nuclei, mesencephalic tectum, tegmental nuclei, torus semicircularis, and dorsal horn and central field of the spinal cord. Only scattered Ucn-immunoreactive axon terminals were observed in the external zone of the medial eminence. The densest accumulations of Ucn-immunoreactive nerve terminals were seen in the granular layer of the cerebellum and cochlear nuclei. Our results suggest that an ortholog of mammalian Ucn occurs in the CNS of the green frog. The distribution of Ucn-like immunoreactivity in Rana esculenta showed many similarities to the distribution in placental mammals. The distribution of Ucn-like immunoreactivity in the anuran CNS was different from that of CRF and sauvagine, so our results suggest that at least three different lineages of the CRF neuropeptide family occur in the anuran CNS.

Urocortin (Ucn), a newly identified member of the corticotropin-releasing factor (CRF) family, is not only expressed in the brain, but also abundantly present in the peripheral tissues, especially in the gastrointestinal tract (GI) as determined by radioimmuoassay. In order to determine the precise localization of urocorin in the GI, we mapped the distribution of urocortin-like immunoreactivity (ir) in the GI of the rat using an immunofluorescence histochemical technique. Ucn, both in the brain and the peripheral tissues, is involved in the regulatory control of host-defense mechanism during stress. In order to study the possible involvement of the sympathetic system in the expression of GI urocortin in response to stress, we examined the effect of chemical sympathectomy on urocortin-ir and its colocalization with tyrosine hydroxylase (TH). UCn was expressed in all parietal cells of the stomach, myenteric and submucosal plexuses as well as in cells in Lieberkühn crypts of the small and large intestine. Most of the acid secreting parietal cells contained both Ucn and TH. Chemical sympathectomy did not affect Ucn immunoreactivity of parietal cells.

The complete amino acid sequence of porcine LH- and FSH-releasing hormone has been provisionally determined by the use on a micro-scale of the combined Edman-dansyl procedure coupled with the selective tritiation method for C-terminal analysis. These procedures were used directly on the digestion products of LH-RH with chymotrypsin and thermolysin, without separation of the fragments. Additional data were provided by high resolution mass spectral fragmentation of LH-RH. On the basis of these results, we propose the following decapeptide sequence for LH-RH: (pyro)Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2.

Levels of PACAP38 were measured in different areas of the chicken brain under various lighting conditions by radioimmunoassay (RIA). Selected groups of animals were maintained under light for 14 h alternating with 10 h of darkness (LD), reversed lighting conditions (DL) and constant light (LL) or constant dark (DD). Daily variations of PACAP levels were observed in the brainstem, diencephalon, telencephalon and retina. In the brainstem and diencephalon, levels of PACAP increased during subjective nighttime, except in the DL group where levels were elevated between 15–21 h. In the telencephalon, the lowest level of PACAP was measured between 12–21 h except in the DL group where two peaks occurred at 18 and 03 h. In the retina, all 4 groups showed a similar level and pattern, with lowest levels during midday hours. No daily variation was observed in the pineal gland. According to the present observations, it is suggested that PACAP levels differ in several areas of the chicken brain under various lighting conditions and photic stimuli do not appear to be the main regulators of the circadian variations of PACAP.

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 expressed 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.

The MtT/S somatotroph cell line should be a growth hormone-releasing hormone (GHRH)-responsive model system for the study of physiological control of growth hormone (GH) transcription because GH secretion from these cells is stimulated by GHRH. To examine the GH transcriptional activity of these cells, endogenous GH mRNA levels were measured using a ribonuclease protection assay following treatment under a variety of hormonal conditions. While omission of serum led to reduction of GH mRNA to 22% of control levels by 2 days and to 8% by 5 days (P0.05 for both), GH mRNA levels were maintained at control values in serum-free medium containing 5 nM dexamethasone and 30 pM triiodothyronine (TDM). However, the addition of 10 nM GHRH under any treatment condition did not significantly alter GH mRNA levels. Characterization of the MtT/S cells showed that GHRH-receptor (GHRH-R) mRNA was detectable by reverse transcription-polymerase chain reaction (RT-PCR) amplification. Measurement of extracellular cAMP showed that the MtT/S cells have basal levels ofor =20 nmol/10(6) cells per h in both serum-containing and serum-free media, and that GHRH had no effect on cAMP levels, suggesting constitutive activation. To rule out the possibility of autocrine stimulation by GHRH produced endogenously, GHRH mRNA was not detectable in MtT/S cells using RT-PCR amplification. The stimulatory G-protein alpha subunit, mutations of which are known to activate adenylate cyclase constitutively in acromegaly, was sequenced but found not to differ from normal pituitary in the regions most commonly mutated. Finally, treatment with 10 microM forskolin, to directly activate adenylate cyclase, increased GH mRNA to 140% of controls in TDM, and to 163% in serum-free medium after 2 days, and to 166% in TDM-treated cells and 174% in serum-free culture after 5 days (all P0.05). Taken together, these data indicate that although MtT/S cells express the GHRH-R, GHRH cannot stimulate adenylate cyclase to increase GH transcription due to constitutive elevation of cAMP levels, by a means that may be similar to that in cases of acromegaly not caused by oncogenic gsp mutations.

Urocortin, a member of the corticotropin releasing factor (CRF) peptide family, has a 45%sequence identity to CRF. Urocortin is ten-times more potent than CRF in increasing CAMP in cells expressing the CRF, receptor, therefore it was postulated to be an endogenous ligand for this receptor. Urocortin possesses the biological activity of CRF, and by activating the CRF(2) receptors, it can directly affect autonomic functions and play an important role in modifying the efferent components of endocrine, immune and behavioral responses to stress.Although urocortin's distribution in the rat brain has been described, with the most abundant urocortin-ir perikarya present in the Edinger-Westphal nucleus (E-WN), little is known about the physiological significance of brain urocortin. Since immediate early gene expression is seen in several midbrain regions, such as in the E-WN, following acute stress, we hypothesized that acute pain stress can result in the activation of the urocortinergic neurons in the E-WN.Fos immunoreactivity, the protein product of the immediate early gene c-fos, was used as a marker of cellular activity. Double-label immunohistochemical and double label immunofluorescence techniques were used in an acute pain stress model to reveal the colocalization of Fos-immunopositivity with urocortin-immunoreactivity (ir) within the E-WN.Our results showed that acute pain stress resulted in the activation of urocortin-ir neurons in the E-WN, peaking at 4 h after acute pain stress, based on the colocalization of Fos-ir with urocortin-ir, and the upregulation of urocortin mRNA transcripts in the E-WN. Based on these results, we suggest that the E-WN is a brain area that shows sustained activation by a painful stressor.

Investigating the cellular events in the pituitary gland, the intracellular cyclic AMP (cAMP) of the neural lobe (NL), intermediate lobe (IL), the inner (IZ-AL) and outer zone (OZ-AL) of the anterior lobe (AL) have been measured during the suckling stimulus. Ten-minutes suckling, parallel to the elevation of plasma PRL, induced a significant increase of cAMP concentration in the IZ-AL. In contrast, 10- and 30-min suckling resulted in a decrease of cAMP level in the NL. Changes in cAMP of the OZ-AL and the IL as well as in the plasma level of alpha-MSH could not be detected. These region-specific changes of cAMP in the pituitary gland during suckling stimulus seems to be related to interacting neuroendocrine signals delivered concomitantly from the hypothalamus and from the NIL to the IZ-AL.

Background and Purpose —Many substances have been shown to reduce brain damage in models of stroke, but mainly when given either before or shortly after the onset of ischemia. Delayed systemic administration of pituitary adenylate cyclase–activating polypeptide (PACAP) has been shown to attenuate the neuronal damage in the hippocampus in a model of global ischemia in rats. The present study examined the neuroprotective action of delayed systemic administration of PACAP38 in a model of transient focal ischemia produced by middle cerebral artery occlusion (MCAO) in rats. Methods —We administered PACAP38 as an intravenous bolus (20 nmol/kg body wt) followed by an intravenous infusion for 48 hours using a micro-osmotic pump at a rate of 160 pmol/μL per hour, beginning 4, 8, or 12 hours after a 2-hour transient MCAO using a filament model. The size of the infarct was determined by examining 2-mm-thick brain sections stained with triphenyltetrazolium chloride, followed by image analysis. Control animals received intravenously 0.1% bovine serum albumin in 0.9% saline as a bolus and infusion at the same time intervals. Results —The administration of PACAP38 beginning 4 hours after MCAO significantly reduced the infarct size by 50.88%. Treatment with PACAP38 starting 8 or 12 hours after the onset of ischemia did not result in a significant reduction of the infarct size, although infarct volumes tended to be smaller than in the control groups. Conclusions —Systemic administration of PACAP38 should be clinically useful for reducing brain damage resulting from stroke even when administration is delayed for several hours.

Expression of pituitary adenylate cyclase-activating polypeptide (PACAP), a neuropeptide with considerable homology to vasoactive intestinal peptide, has been shown to be stimulated by gonadotropins in the ovary. The present studies further evaluated the cell-type specific expression and gonadotropin regulation of PACAP type I receptor (PACAPR) messenger RNA in immature rat ovaries and in cultured preovulatory follicles. Northern blot analysis of ovaries obtained from prepubertal rats revealed the increased expression of PACAPR during prepubertal development. The major cell types expressing PACAPR messenger RNA were granulosa cells of large preantral follicles. Treatment of immature rats with PMSG caused a decrease in ovarian PACAPR expression. In contrast, treatment with human (h) CG at 2 days after PMSG treatment stimulated ovarian PACAPR messenger RNA within 3–6 h in granulosa cells of preovulatory follicles. Treatment of cultured preovulatory follicles in vitro with LH further confirmed the time- and ...

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a pleiotropic neuropeptide and its specific receptor (the PAC(1) receptor) is widely distributed in the rat brain. It has been reported that alternative splicing of the region encoding the third intracellular loop of the PAC(1) receptor generates six isoforms which are differentially coupled to signal transduction pathways, but the precise distribution and localization of these splice isoforms in the brain remain to be determined. Using the initial specific primer pairs which correspond to the 'hip' or 'hop' types of receptors for the solution-phase reverse transcription-polymerase chain reaction (RT-PCR), we demonstrated that the major splice variants of the PAC(1) receptor in various regions of the rat brain are the short splice isoform 'PAC(1)-R-s' which does not contain either the 'hip' or 'hop' cassette and the another splice isoform, 'PAC(1)-R-hop', which contains the 'hop' cassette. With an innovative molecular histochemical technique, in situ RT-PCR, we determined that these two splice isoforms are both intensely expressed in the mitral cells of the olfactory bulb, the Purkinje cells of the cerebellum, the pyramidal cells of the hippocampus and neocortex, and many neurons in the nuclei of hypothalamus and thalamus as well as other regions. The initial mapping of the cell type-specific expression of these two splice variants of the PAC(1) receptor provides the basis for a better understanding of the functional significance of the PAC(1)-R and its ligand PACAP in various brain regions.

Pituitary adenylate cyclase activating polypeptide 38 (PACAP38) is a novel peptide hormone and has a variety of biological actions. In studies of the physiological behavior of endogenous PACAP, the determination of PACAP38 levels in biological materials requires a highly sensitive and specific method. Therefore, we developed a sensitive bioluminescent enzyme immunoassay (BL-EIA) for PACAP38 using acetate kinase (AK) as a reporter enzyme and the luciferin–luciferase reaction. Accordingly, we developed BL-EIA using biotinylated PACAP38 as a labeled antigen and biotinylated AK–streptavidin complex as a detector of biotin on solid phase. The measurable range was 62–16000 pg ml −1 for PACAP38 by the proposed BL-EIA. The PACAP38 concentration of various tissue extracts of rat and plasma of rat and human could be measured by the proposed BL-EIA. Furthermore, a high degree of correlation for various samples was found between the results obtained by BL-EIA and radioimmunoassay.

Pituitary adenylate cyclase-activating polypetide (PACAP) exists in two amidated forms, PACAP38 and PACAP27, which are expressed in the magnocellular and parvocellular neurons of the paraventricular nucleus (PVN) and the magnocellular neurons of the supraoptic nucleus (SON) of the hypothalamus. The prohormone convertases PC1 and PC2, subtilisin-like PCs of the Kex2 family, are expressed in neuroendocrine cells. Immunocytochemistry and in situ hybridization of PC1 and PC2 in the hypothalamus have shown that PC1 and PC2 are also present in the PVN and SON. Therefore, it is possible that the precursor of PACAP is processed by PC1 and/or PC2 in the hypothalamic nuclei and then converted to its mature forms. To test this hypothesis, rat pituitary GH4C1 cells were supertransfected with human PACAP cDNA and either rat PC1 or PC2 cDNA. The acid extracts of these cells were analyzed by reversed-phase HPLC for proPACAP, PACAP38 and/or PACAP27 radioimmunoassays using three antibodies with different recognition sites, and then bioassayed for the ability to stimulate adenylate cyclase. The cells transfected with PACAP cDNA alone yielded PACAP-like immunoreactivity (PACAP-li) corresponding to molecular weights between 15 and 20 kDa without PACAP bioactivity. Cotransfection of these cells with PC1 or PC2 generated PACAP-li, which coeluted with synthetic PACAP38 and PACAP27, respectively. Western blot also revealed 4.5- and 3.0-kDa PACAP-li bands, which correspond to the molecular weights of PACAP38 and PACAP27, respectively. The HPLC fractions containing PACAP-li, which were coeluted with synthetic PACAP38 and PACAP27, showed marked bioactivities. These findings suggest that the precursor of PACAP expressed in the PVN and SON of the hypothalamus could be efficiently processed by PC1 and PC2, and then converted to mature, bioactive PACAP38 and PACAP27.

Radioimmunoassay has revealed an abundance of PACAP in the rat testis. In the present study, a novel stamp preparation together with light microscopic immunohistochemistry were used to investigate in detail the intracellular localization of PACAP-like immunoreactivity (PACAP-LI) in rat germ cells. Samples were obtained by pressing the freshly cut surfaces of the testes against glass slides. PACAP-LI was clearly identified in developing acrosomes using five antisera which recognize PACAP 38, or both PACAP 27 and PACAP 38. Immunoreactivity with the antisera specific to PACAP38 was strictly localized in the developing acrosomes of the spermatids but vanished in the mature spermatids. Using an antiserum which detects PACAP 27 specifically, little staining was observed. Based on the specificities of antisera used, it was suggested that the PACAP-LI in the acrosomes represents mainly PACAP 38-LI. In addition, the present results supported the usefulness of the stamp preparation for immunohistochemical study of testicular tissues.

The bed nucleus of the stria terminalis (BSTL), which is known to be involved in the modulation of stress responses, exhibits a dense network of pituitary adenylate cyclase activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) immunoreactive (ir) fibers. The origin of the PACAP-ir fibers is unknown, and the origin of the VIP-ir fibers remains uncertain. The most important brain regions connected to the BSTL are the amygdaloid nuclei, the paraventricular and ventromedial hypothalamic nuclei, mesencephalic periaqueductal grey, the dorsal and linear raphe nuclei, the parabrachial nucleus, and the dorsal vagal complex. After microinjecting cholera toxin B subunit (CTB) in the BSTL as a retrograde tracer, neurons were double labeled for CTB and PACAP or VIP immunohistochemistry and the cells from which the PACAP- and VIP-ir fiber networks in the BSTL originated were identified. Cholera toxin B subunit labeled and VIP-ir cells were found in the mesencephalic periaqueductal grey and the dorsal and linear raphe nuclei, but no double labeled cells were seen in the amygdaloid nuclei or the hypothalamic region. CTB- and PACAP-ir neurons were observed in the paraventricular nucleus and the dorsal vagal complex. No double labeled perikarya were seen in the parabrachial nucleus or in the amygdaloid nuclei.

The complementary DNA encoding pituitary adenylate cyclase-activating polypeptide (PACAP) has been cloned from two species of teleost fishes, the Sockeye salmon and the Thai catfish, and the amino acid sequence of PACAP has been determined in another teleost, the stargazer. However, to date, the detailed distribution of PACAP immunoreactivity has never been investigated in the fish brain. In the present study, we have determined the localization of PACAP-immunoreactive neurons in the central nervous system of a primitive teleost fish, the European eel Anguilla anguilla, using an antiserum raised against PACAP27. PACAP-positive perikarya were exclusively observed in the diencephalon, i.e. in the preoptic nucleus of the hypothalamus and in the dorsal and ventral nuclei of the thalamus. PACAP-immunoreactive fibers were detected in various areas of the brain, notably in the ventral telencephalon, the diencephalon, the mesencephalon, the cerebellar valvula, and the medulla oblongata. In addition, a dense accumulation of PACAP-containing nerve terminals was found in the pars distalis of the pituitary. The PACAP-like immunoreactivity contained in the eel brain was characterized by HPLC analysis combined with RIA quantification. The major form of PACAP-immunoreactive material coeluted with mammalian PACAP38. Molecular cloning of the PACAP precursor has previously shown that in fish, PACAP and GH-releasing hormone (GHRH) originate from the same precursor. We have thus investigated the effects of PACAP and GHRH on GH secretion from eel pituitary cells in primary culture. Dose-response experiments revealed that PACAP27 and PACAP38 possessed the same efficacy, but PACAP38 was 12 times more potent than PACAP27 in stimulating GH release (ED50 = 4.3 x 10(-10) and 3.5 x 10(-9) M, respectively). In contrast, GHRH, even at a high concentration (10(-6) M), had no effect on GH release. Taken together, these data indicate that in the eel, PACAP may play a significant role in the regulation of somatotrope cells: 1) PACAP-immunoreactive neurons are exclusively located in the diencephalon and send numerous projections in the pars distalis; and 2) PACAP, but not GHRH, dose dependently stimulates GH secretion from cultured eel pituitary cells.