摘要:

The distribution of neuropeptide Y-like immunoreactivity (NPY-LI) was investigated by immunohistochemistry and radioimmunoassay (RIA) in the brain of the Djungarian hamster (Phodopus sungorus) held under either long or short photoperiods. In the diencephalic and telencephalic structures studied, distinct patterns of NPY-LI were basically consistent in male and female animals of both groups. NPY levels detected by RIA from tissue samples taken at six time points throughout the 24-hour cycle were in the range of 15-60 pmol/ mg protein in the diencephalon or below 5 pmol/mg protein in cerebral cortex. In the diencephalon, immunoreactive structures were seen in the preoptic, peri- and paraventricular, supraoptic, anterior, lateral, dorso- and ventromedial hypothalamic nuclei and in the median eminence. The suprachiasmatic nuclei exhibited a dense innervation by NPY-LI terminals mainly in its ventrolateral subdivision. NPY levels in the suprachiasmatic nucleus were nocturnal-ly augmented under long-day, but not under short-day conditions. The quantification of NPY in the paraventricular nucleus revealed a decrease at night in long-day animals and a small nocturnal augmentation in short-day hamsters. In the pineal gland and habenular nuclei, varicose fibers were observed which appeared mainly perivascular in location (pineal) or formed a dense plexus (habenular nuclei). Pineal NPY contents fell during the night in long-day animals and were relatively constant in short-day hamsters. NPY-LI structures were also observed in the metathalamic intergeniculate leaflet and in a variety of telencephalic structures including the cerebral cortex, caudate nucleus puta-men, lateral septal nucleus, bed nucleus of the stria terminalis and amygdala.

ISSN:0028-3835    

DOI:10.1159/000126856

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Melanin-concentrating hormone (MCH) is a cyclic peptide which is predominantly synthetized in the hypothalamus of fish and mammalian brains. In the present paper we examined the expression of MCH mRNA and pro-MCH-derived peptides, i.e. MCH and neuropeptide-(N)-glutamic acid (E) isoleucine (I) amide (NEI), in peripheral tissues of adult rodents. By means of polymerase chain reaction (PCR) of reverse-transcribed RNA, low levels of MCH gene transcripts were detected reliably in testis, stomach, and intestine of Sprague-Dawley and Wistar rats, whereas strong expression was found in hypothalamus. Subsequent sequence analysis of the PCR products verified the authenticity of MCH mRNA found in hypothalamus and stomach. The length of MCH RNA species was measured by Northern blot and multiple MCH RNA species were detected in both rat species. Shortest polyadenylated tails were found in MCH RNAs isolated from the peripheral organs by comparison with hypothalamus MCH RNAs of Wistar rats. In order to localize MCH expression in gastrointestinal and genital tracts of Wistar rats we performed in situ hybridization with specific 33P-labeled oligo-probes joined to immunocytochemical studies with rat MCH or NEI antisera. In testis, the MCH transcripts and pro-MCH-derived peptide immunoreactivities were found at the periphery of the seminiferous tubules, suggesting expression in Sertoli cells. Studies with MCH oligoprobes and antisera directed towards MCH, NEI and αA-inhibin revealed similar pattern of expression in isolated Sertoli cells from Swiss mice, indicating that MCH RNA species were actually synthesized and translated in these cells. In the gastrointestinal (GI) tract, the cells expressing MCH RNA species and pro-MCH-derived peptides were predominantly expressed in the antral portion of the stomach and duodenum. Strikingly, distinct oligoprobes, recognizing antisense MCH transcript, revealed a pattern of hybridization in the GI tract similar to this observed with oligoprobes revealing the mature MCH mRNA. Furthermore, total RNA from the pyloric junction, duodenum, jejunum, ileum and hypothalamus as well appeared to contain RNA complementary to MCH mRNA suggesting therefore that antisense MCH RNA species may play a general role in regulation of MCH synthesis. Taken together, our present and previous data indicate that authentic MCH RNA species and translational products are expressed in various rodent tissues at the periphery. The cellular location suggests that MCH and associated peptides may play a role in spermatogenesis and in digestive processes

ISSN:0028-3835    

DOI:10.1159/000126857

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

The presence and distribution of bombesin (BBS)/gastrin-releasing peptide (GRP)-like immunoreactivity (IR) was examined in the goldfish pituitary and forebrain. BBS/GRP-like IR nerve fibres were consistently observed throughout the pituitary neurointermediate lobe (); occasionally, BBS/GRP-like material was localized in cells and few fibres within the pars distalis. Within the goldfish forebrain, sparse, fine-beaded BBS/GRP-like IR fibres and few perikarya were detected in the preoptic hypothalamus. BBS/GRP-like IR material was also present in the ventro-posterior hypothalamus and the hypothalamic inferior lobes, and, in particular, within the nucleus lateral tuberis pars anterioris (NLTa) and nucleus lateral tuberis pars posterioris (NLTp), nucleus anterior tuberis (NAT), nucleus recessus lateralis (NRL), nucleus recessus posterioris (NRP), and the nucleus diffusus lobi inferioris (NDLI). Several BBS/GRP-like IR perikarya were observed in periventricular regions of the NLT, NRL, and NRP. Finally, BBS/GRP-like IR material was detected in the nucleus habenularis, the nucleus rotundus, several thalamic nuclei, and the optic tectum of the dorso-posterior diencephalon. The presence of BBS/ GRP-like IR material within the preoptic hypothalamus, hypophysial stalk, and in the pituitary suggests that BBS-like peptides may regulate pituitary hormone release in fish. Perifusion of goldfish pituitary fragments with initial pulses of 0.1,10,100 or 1,000 nMBBS stimulated both growth hormone (GH) and gonadotropin (GtH-II) release. Repeated pulses of the same dose of BBS generally stimulated GH and GtH-II release to a similar magnitude. These studies provide initial evidence that BBS/GRP-like peptides are present within the central nervous system of teleost fish. The anatomical distribution of BBS/ GRP-like IR in goldfish hypothalamic feeding center supports our previous report indicating a role for BBS in the central regulation of food intake in fish. Additionally, the presence of BBS/GRP-like IR material in the pituitary and brain areas associated with the regulation of anterior pituitary hormone secretion, as well as evidence demonstrating a direct action of BBS at the level of the goldfish pituitary to modify GH and GtH-II secretion, indicates that BBS/ GRP-like peptides likely act to regulate pituitary hormone release in teleosts.

ISSN:0028-3835    

DOI:10.1159/000126858

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a novel 38-residue neuropeptide which stimulates adenylate cyclase activity in rat pituitary cells as well as in other neuronal and non-neuronal tissues. In this study we have investigated whether PACAP27 and PACAP38 may stimulate either cyclic AMP accumulation or phosphoinositide formation in cultured cerebellar granule cells. In cultures at 8 days of maturation in vitro (DIV), a 15-min exposure to PACAP27 or PACAP38 equally promoted a concentration-dependent increase in intracellular cAMP content: the effect was significant at 1-5 nM and maximal between 10 and 100 nM, while VIP was 1,000-fold less potent in elevating cAMP levels. In the presence of 3-isobutyl-1-methylxan-thine (200 µM), stimulation by PACAP was present already at 0.1 nM and was maximal (6-fold increase) at 1 nM. A rapid elevation in intracellular cAMP (about 80%) was observed within a 30-second exposure to 10 µM PACAP38 or PACAP27; the maximal activity of PACAP was present between 15 and 30 min and progressively declined at 60 min without reaching basal values. PACAP27 and PACAP38, but not VIP, were also able to stimulate inositol phospholipid hydrolysis: PACAP38 (EC50: 0.16 nM) was 10-fold more potent than PACAP27 (EC50: 2.1 nM) in stimulating [3H]inositol phosphate formation. The effect of PACAP was rapid: fractionation of [3H] inositol phosphates revealed that inositol trisphosphate and inositol bisphosphate increased earlier (within 20 s) than inositol monophosphate (within 60 s). Stimulation of inositol phospholipid hydrolysis by PACAP was not mediated through the activation of the adenylate cyclase-cAMP system because neither 10 µM forskolin nor VIP (1–10 µM) were able to affect inositol phospholipid turnover. Interestingly, while the cAMP response was already present (and maximal) at 2 DIV, PACAP increased phosphoinositide hydrolysis only at 4 DIV. Our results provide clear evidence for the presence of PACAP receptors linked to both the adenylate cyclase-cAMP system and the phosphoinositide turnover in cerebellar granule

ISSN:0028-3835    

DOI:10.1159/000126859

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Nicotinic cholinergic agonists stimulate ACTH secretion by a central mechanism involving brainstem catecholamines. In vivo microdialysis studies were conducted to measure the release of norepinephrine (NE) in the hypothalamic paraventricular nucleus (PVN) in response to the administration of nicotine (Nic) or another nicotinic cholinergic (NAch) agonist, cytisine (Cyt), directly into the IVth ventricle. Alert, freely mobile rats, equipped 24 h previously with a chronic guide cannula in the IVth ventricle and microdialysis probe in the PVN, were injected with artificial cerebrospinal fluid (CSF, 500 nl/60 s), Nic (1–5 µg), or Cyt (1–25 µg) after three 20-min baseline samples had been taken. Analysis of the dialysates by HPLC with electrochemical detection demonstrated the dose-dependent secretion of PVN NE to Nic or Cyt with ED50s of approximately 1 or 6 µg, respectively; these were completely blocked by prior IVth ventricular injection of the NAch antagonist, mecamylamine (4 µg). In contrast, α-bungarotoxin, which antagonizes the action of NAch agonists by acting through the α7bungarotoxin-type NAchR, failed to reduce the NE response to Nic. Partial, but significant desensitization of NE secretion in response to a second injection of Nic (2.5 or 5 µg) 100 min after the first was seen, whereas NE responses to the second injection of Cyt (5 or 25 µg) were completely desensitized. However, cross-desensitization of each agonist to the other did not occur. This may reflect heterogeneity of the NAch receptor subtypes involved. The results of this study establish a correlation between the action of nicotine on brainstem norepineph-rinergic regions and the resultant release of NE in the PVN, which would lead to the release of ACTH se

ISSN:0028-3835    

DOI:10.1159/000126860

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Galanin (GAL) is a 29-amino acid peptide that is present in the hypothalamic magnocellular neurons of the rat supraoptic nucleus (SON) and paraventricular nucleus (PVN). Since previous studies revealed a possible role of GAL in the hydroosmotic regulation, we have investigated the effects of GAL on the vasopressin (AVP) mRNA content in the hypothalamic magnocellular neurons. We demonstrated by in situ hybridization (ISH) and immunohistochemistry that 100 pmol of GAL or GAL fragment (1-16) injected into the lateral ventricle of anesthetized dehydrated male rats induced a rapid (10 min time interval) decrease of AVP mRNA and AVP content in the magnocellular cell bodies of SON and PVN. These effects were quantified on an autoradiographic film and were also obvious at the cellular level by using ISH with a radiolabeled or digoxigenin-labeled oligonucleotide probe. Oxytocin mRNA content is not altered by the same injection either in dehydrated male or lactating female rats. Under the same conditions of lactation, AVP mRNA content is not modified and the i.c.v. injection of GAL has no effect. GAL antagonist (M15) injection suppressed the GAL-induced decrease of AVP mRNA in the dehydrated rats and increased AVP mRNA level in control rats. The efficacy of M15 in antagonizing GAL effects on AVP mRNA suggests the involvement of GAL receptors in the regulation of the vasopressinergic cell bodies. Moreover, endogenous GAL seems to depress the AVP mRNA content of SON and PVN in vivo. The possible origin of endogenous GAL and the mechanisms by which GAL can regulate the AVP mRNA content are also discussed.

ISSN:0028-3835    

DOI:10.1159/000126861

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

We previously reported that gonadal steroids modify the expression of arginine vasopressin (AVP) in the hypothalamus of rats administered 2% sodium chloride solution for 5 days. Gonadectomy prevented, and testosterone (T) replacement restored, enhanced AVP mRNA levels in the supraoptic nucleus (SON) of male rats receiving this hyperosmotic challenge. The present study investigated the effects of the androgenic and estrogenic metabolites of T on hypothalamic AVP mRNA levels in response to chronic hyperosmolality. Gonadectomized male rats receiving 2% NaCl for 5 days and treated with T, dihydrotestosterone (DHT), or DHT + estradiol (E2), but not E2 alone or empty implants, had increased AVP mRNA levels compared to gonadectomized animals receiving tap water. Our results support a role for T and DHT-mediated effects upon the enhanced accumulation of AVP mRNA in the SON of male rats receiving a chronic hyperosmotic challenge.

ISSN:0028-3835    

DOI:10.1159/000126862

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Previous studies have shown that many treatments that stimulate the peripheral secretion of oxytocin (OT) and vasopressin (AVP) from the pituitary simultaneously increase the levels of these peptides in the cerebrospinal fluid (CSF). Since osmotically and nonosmotically stimulated pituitary secretion of OT and AVP is markedly blunted in hyponatremic rats, the present studies evaluated whether central OT and AVP secretion into the CSF is similarly inhibited during sustained hyponatremia. Adult male rats with indwelling cisterna magna cannulae were rendered hyponatremic (plasma [Na+] <110 mmol/l) by s.c. infusion of desmopressin (dDAVP; 10 ng/h) in combination with ingestion of a liquid diet for 3 days, then subjected to osmotic (i.v. or i.p. injection of 2 M NaCl; HS) or nonosmotic (6 mmol/kg of 0.15 M LiCl i.p.) stimulation. In normonatremic rats both i.v. and i.p. HS caused marked increases in plasma OT and AVP levels 30 min after treatment. Significant elevations of OT, but not AVP, were also present in CSF. Despite similar increases in plasma Na+ concentrations, plasma OT responses in the hyponatremic rats were absent after HS i.v. and were significantly blunted after HS i.p., but neither group had increased plasma AVP. In parallel with the plasma results, CSF OT responses were absent in hyponatremic rats given HS i.v. and significantly blunted in hyponatremic rats given HS i.p., but neither group had increased CSF AVP. Nonosmotic stimulation with isotonic LiCl increased OT levels both in plasma and CSF in normonatremic rats 20 min after treatment. Although plasma OT responses were significantly blunted in the hyponatremic rats, the equivalent decreases in the CSF OT responses did not reach statistical significance. These results demonstrate that sustained hyponatremia inhibits both central and neurohypophyseal OT secretion in response to acute osmotic stimuli. The parallel changes in CSF and plasma OT levels under hyperosmolar and hypoosmolar conditions supports the likelihood that the increased CSF OT found during osmotic stimulation is of magnocellular origin, possibly reflecting dendritic release. The incomplete inhibition of plasma and CSF OT responses seen after i.p. injection of HS and LiCl in hyponatremic rats further indicates that nonosmotic afferent inputs can override osmotic inhibition of magnocellular OT neurons.

ISSN:0028-3835    

DOI:10.1159/000126863

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Although the presence of thyrotropin-releasing hormone (TRH) in the posterior pituitary (PP) was reported more than one decade ago, knowledge on its origin, regulation and functional significance is lacking. In the present study we investigated the regulation of TRH in the rat PP. Analysis by specific RIA, anion and cation exchange chromatography and reverse-phase HPLC showed that all TRH immunoreactivity in the PP is accounted for by authentic TRH. Induction of hyperthyroidism with thyroxine increased levels of TRH in the PP by 20%, whereas in methimazole-treated, hypothyroid rats the content decreased by 25% versus untreated, euthyroid controls. Food deprivation for 3 days increased levels by 35% and refeeding completely normalized TRH content again. Also 14–17 days after castration, TRH in the PP was increased by 25% while testosterone substitution prevented this increase. Castration did not affect proTRH mRNA levels in the hypothalamus. One week after adrenalectomy or daily subcutaneous dexamethasone injections, TRH content in the PP was not affected. Treatment with disulfiram, an inhibitor of the peptidylglycine α-amidating monooxygenase (PAM), reduced levels of TRH in the PP by 20%. ProTRH and PAM mRNA levels were not affected in the hypothalamus by this treatment. Since TRH in the PP has been suggested to play a role in prolactin (PRL) release, we determined the content of TRH in the PP during a 6-hour suckling stimulus that increased PRL levels in peripheral blood 30-fold. Whereas TRH in the median eminence increased by 35%, 6 h after the initiation of suckling, TRH levels in the PP remained constant. In conclusion, (1) authentic TRH accounts for all TRH immunoreactivity in the PP, (2) TRH content in the PP is increased in conditions in which hypothalamic TRH release is reportedly decreased (hyperthyroidism, starvation, castration) and decreased when TRH release is increased (hypothyroidism) – its levels may thus be used as a parameter of TRH content in hypothalamic hypophysiotropic neurons; (3) the changes in TRH levels in the PP in conditions that alter thyroid-stimulating hormone (TSH) levels in peripheral plasma suggest a role in TSH secretion, and (4) TRH in the PP does not seem to be important for the suckling-induced PRL rel

ISSN:0028-3835    

DOI:10.1159/000126864

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Previous studies have shown that melanotrope cells of the pars intermedia of Rana ridibunda are inhibited by dopaminergic D2 agonists and stimulated by β-adrenergic agonists. In the present study, we have examined the possible involvement of α-adrenoreceptors in the regulation of frog melanotrope cells. Reversed-phase HPLC analysis combined with electrochemical detection revealed the presence of both dopamine and noradrenaline in pars intermedia extracts (74.1 and 3.2 ng/mg protein, respectively), while adrenaline was undetectable. Administration of graded doses of noradrenaline and adrenaline (from 0.1 to 10 µM) to perifused frog neurointermediate lobes induced a dose-dependent inhibition of α-MSH release. The inhibitory effect of adrenaline was partially blocked by the D2-dopaminergic antagonist sulpiride and totally suppressed by concomitant administration of sulpiride and yohimbine (an α2-adrenergic antagonist). Conversely, in the presence of sulpiride, noradrenaline provoked a strong stimulation of α-MSH secretion which was totally blocked by the β-adrenergic antagonist propranolol. Taken together, our results indicate that endogenous catecholamines may exert a complex regulatory action on frog melanotrope cells through activation of dopaminergic D2, α2- and β-adrenergic r

ISSN:0028-3835    

DOI:10.1159/000126865

出版商:S. Karger AG    

年代:1995

数据来源: Karger