摘要:

Indirect immunocytochemistry of corticotropin-releasing factor (CRF) and peptide histidine isoleucine amide (PHI) was performed by the use of antibodies raised to CRF and PHI. The staining intensity was quantitated by using an automated microfluorimeter. CRF and PHI immunoreactive fibres showed a similar pattern of distribution in the zona externa of the median eminence of the rat hypothalamus. Administration of colchicine (50 µg i.c.v.) resulted in the appearance of PHI and CRF immunoreactive cell bodies in the parvocellular part of the paraventricular nucleus. The PHI immunoreactive cell bodies were of low intensity and less abundant than those stained with the CRF antisera. Microfluorimetric measurements of the immunostaining in the median eminence showed parallel changes of PHI and CRF immunostaining after adrenalectomy, administration of reserpine and/or pargyline. In order to evaluate whether these data demonstrate that PHI and CRF are colocalized in hypothalamic neurons, we studied the specificity of PHI immunostaining by the use of a nonbiological gelatin model. Although CRF and PHI do not show structural homologies, the PHI antisera caused staining of PHI containing gels (range: 0.001–1 µM) but also of rat CRF (rCRF)-containing gels (range: 10–300 µM). In addition, preincubation of one of the PHI antisera with PHI or rCRF both caused a concentration-dependent quenching of the immunostaining in PHI- and CRF-containing gels and in preparations of the median eminence. Again, higher concentrations of rCRF (100 µM) than PHI (0.1 µM) were needed to show immunoinhibition, suggesting that the PHI antiserum has much lower avidity for native and fixed rCRF than for native and fixed PHI. We conclude that PHI immunostaining in the rat median eminence as found under the conditions used, is due, at least partially, to cross-reaction of the PHI antisera w

ISSN:0028-3835    

DOI:10.1159/000124666

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Serum testosterone and androstenedione levels were lower in the subordinate female talapoin monkeys of four social groups than either dominant or intermediate-ranking females. This was found in both intact or ovariectomized (oestrogen-treated) animals, which suggests that androgen from the adrenals contributed to this rank-related endocrine effect. These differences disappeared when the females were housed singly, levels in all animals becoming similar to those in subordinates in the group cage. There were no rank-related differences in progesterone levels during either the follicular or luteal phase of the cycle in intact females, or in those of ovariectomized females of different rank, but cortisol was highest in dominant group-living animals in these experiments. Significant correlations were found between androgen levels in group-living females and the amount of sexual interest shown in them by males; the amount of aggressive interaction involving each female did not correlate with her androgen levels. Social rank is defined according to the direction, not the amount, of aggression. These findings suggest that the social hierarchy regulates androgen levels in these female monkeys; there may also be effects on the ability of females to respond to their own, or to administered, androgen. Similar findings have been made previously in male talapoins. Since androgens fill a critical role in the sexual behaviour of both sexes in primates, this may be a neuroendocrine mechanism of general significance relating behaviour to social rank.

ISSN:0028-3835    

DOI:10.1159/000124667

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Our laboratory has previously described the widespread distribution of an immunoreactive and bioactive rat growth hormone (rGH)-like protein in rat brain. It has also been demonstrated that regulation of pituitary rGH secretion is at least partly mediated by a short-loop negative feedback system. In such a system, increased levels of rGH, acting at a suprapituitary locus, would decrease pituitary GH secretion. Thus, the present study has dealt with attempts to further investigate the hypothesis that one function of brain-based rGH might be as a mediator of the short-loop negative feedback system controlling pituitary rGH release. If brain-based rGH were to function as a mediator of such a system, then in situations where serum rGH levels are decreased, brain rGH concentrations should increase, indicating activation of a negative feedback loop. In the present communication we report that significantly decreased serum GH levels in oophor-ectomized and in thyroidectomized rats were coupled with a significant increase in rGH concentrations in the hypothalamus and in the amygdala. By contrast, adrenalectomy, which was not associated with any changes in levels of GH in serum caused no perturbations in levels of rGH in the brain. These discordant changes in serum and brain-based rGH are findings compatible with the hypothesis that one function of brain-based rGH is as a mediator of the short-loop negative feedback system regulating the release of pituitary GH.

ISSN:0028-3835    

DOI:10.1159/000124668

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

In situ hybridization has been used to identify specific hypothalamic magnocellular neurons, in normal and Brattleboro rats, that contain vasopressin (VP) or oxytocin (OT) mRNA. The subnuclear distribution of identified neurons in hypothalamic magnocellular nuclei after hybridization with several probes specific for OT or VP mRNA was in direct agreement with immunocytochemical descriptions of the distribution of cells containing VP or OT hormone. The number of grains per cell suggested that Brattleboro rats contained greater levels of OT mRNA, while hybridization with VP probes produced fewer grains in tissue from Brattleboro rats compared to normal rats. This paper provides the first cell-by-cell description of VP gene expression in the Brattleboro rat and demonstrates that VP gene transcription is confined precisely to the magnocellular neurons that normally synthesize VP hormone in normal rats.

ISSN:0028-3835    

DOI:10.1159/000124669

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Rats were injected through the carotid artery (cephalad direction) with 18.9 µCi of either 125I-Arg 101-Tyr 126 atrial natriuretic factor alone or together with an excess of unlabeled hormone. At 2 min after injection, all rats were fixed in vivo by perfusion and serial sections of the whole brain were processed for light microscope radioautography. The radioautographic reaction produced by 125I-atrial natriuretic factor alone was localized in all circumventricular organs (except the subcommissural organ), the smooth muscle cells and endothelial cells of arteries, arterioles, veins, venules, the endothelial cells of intraparenchymal capillaries and the epithelial cells of the choroid plexus. In rats which received 125I-atrial natriuretic factor plus an excess of unlabeled hormone, the radioautographic reaction was reduced by 70–90%. Binding sites are thus localized in regions of the brain, some of them involved in the central monitoring of blood pressure and osmolarity. In addition, the presence of binding sites in the cerebral vasculature and in the epithelium of the choroid plexus suggests that circulating ANF may play a role in the control of cerebral blood flow and in the production of vertebrospinal flu

ISSN:0028-3835    

DOI:10.1159/000124670

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

We have recently purified a novel pituitary polypeptide, designated 7B2. Subsequently, we developed a sensitive and specific radioimmunoassay (RIA) for this novel polypeptide. Our aim in the present study was to investigate the release of 7B2 from rat pituitary induced by various hypothalamic factors [luteinizing hormone-releasing factor (LH-RH), corticotropin-releasing factor (CRF), and growth hormone-releasing factor (GRF)]. The anterior pituitaries were removed from rats and immediately dispersed enzymatically (a mixture of collagenase/dispase/deoxyribonuclease/chicken serum) and plated on collagen-coated multiwell plates in culture medium containing 10% fetal bovine serum. After 2 days of attachment period, the medium was replaced with fresh medium every 24 h. The primary cell culture was incubated with various concentrations of LH-RH, CRF or GRF. Subsequently, the concentrations of IR-7B2, IR-LH, IR-FSH, and IR-ACTH released into the medium were quantified by specific RIA. LH-RH, at a concentration as low as 7.5 ng/ml (6 × 10–9 M; dose range 7.5–60 ng/ml) stimulated the release of IR-7B2, IR-LH, and IR-FSH, by 2- to 3-fold, 17- to 18-fold, and 3-fold, respectively, over basal levels. No significant increase of IR-7B2 was observed when stimulated by CRF or GRF at doses as high as 100 ng/ml. In addition, K+ (50 mM) stimulated the release of all the peptides measured. In conclusion, our studies suggest that the novel peptide 7B2 is under LH-RH control and indirectly confirm the immunohistochemical results of its cellular co-localization in FSH and LH c

ISSN:0028-3835    

DOI:10.1159/000124671

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The effects of cholinergic antagonists on vasopressin (VP) release were studied in an organ-cultured, compartmentalized, rat hypothalamo-neurohypophysial system which allows selective application of stimuli to either hypothala-mus or pituitary without disrupting axonal connections. Release of vasopressin from the neurohypophysis was measured by radioimmunoassay. Hexamethonium (10–5M) and atropine (5 × 10–5M) were tested both alone and in combination with hypothalamic osmotic stimulation (+15 mosm/kg H2O). In hypothalamus, neither hexamethonium nor atropine had any effect on basal VP release from pituitary. Hexamethonium, but not atropine, prevented the increase in VP release produced by increased osmolality of the hypothalamus side culture medium. In contrast, hexamethonium had no effect when applied to pituitary side, whereas atropine suppressed both basal and osmotically stimulated VP release. Atropine had no effect on basal or KC1-induced VP release in detatched neural lobes. Acetylcholine (Ach) (10–5M) to pituitary plus simultaneous hypothalamic stimulation (osmotic or 10–5M Ach) did not increase VP release above the hypothalamic stimulus alone. The results support a role for a hypothalamic excitatory nicotinic mechanism in osmoregulation. The presence of a muscarinic mechanism affecting VP release in pituitary was reconfirmed, but the data did not support the hypothesis that Ach stimulates VP release in pituitary by a presynaptic facilitatory m

ISSN:0028-3835    

DOI:10.1159/000124672

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Dihydropyridines that have been shown in studies on other tissues either to facilitate Ca influx (BAY K 8644) or depress it (nimodipine and nifedipine) were examined for their effects on the secretory activity of the melanotrophs. Isolated mouse neurointermediate lobes, cultured for a week or longer to allow the nerves to degenerate, were perifused and output of MSH activity was measured by bioassay. The Ca-channel agonist BAY K 8644 augmented secretion under basal conditions and potentiated secretion evoked by 30 mM K+, a submaximally depolarizing concentration. The stimulant effect on secretion under basal conditions persisted in the presence of tetrodotoxin (which blocks the action potentials, Na spikes, in the melanotrophs) but was lost when Ca2+ was omitted or nimodipine added. The results are considered to support the view that the prominent basal secretory activity in these cells, as well as that evoked by excess K+, involve the inward flux of Ca2+ through dihydropyridine-sensitive Ca channels. If the stimulant and inhibitory effects of the dihydropyridines on basal secretion are to be attributed to actions on voltage-regulated Ca channels, as the results from other tissues would suggest, then such channels in the melanotrophs are different from those previously described in other tissues.

ISSN:0028-3835    

DOI:10.1159/000124673

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

We readdressed the question of whether or not rat adenohypophyseal vasopressin receptors have a ligand selectivity which is similar to that of the V1 subtype of vasopressin receptors. Vasopressin analogues substituted in positions 7 and 1 were used. By incubating rat anterior pituitary quarters or by perifusing rat isolated anterior pituitary cells the effect of the vasopressin analogues on the release of β-endorphin-like or adrenocorticotropin-like immunoreactive was examined. The replacement of the proline residue in position 7 by sarcosine or N-methyl-alanine did not change the maximum effect reached but increased the EC50 values 20- or 5-fold, respectively, when compared with arginine vasopres sin. This decrease in β-endorphin-releasing activity was no longer observed after additional removal of the α-amino group of cysteine in position 1. Since these substitutions are known to drastically reduce vasopressor activity, these data sugges that the β-endorphin-releasing activity of vasopressin can be dissociated from its V1 receptor activity. Vasopressin ana logues substituted in position 7 and with deaminopenicillamine or β-mercapto-ββ-cyclopentamethylenepropionic acid it position 1 were found to be weak antagonists of the β-endorphin-releasing activity of vasopressin. Since these analogue: are potent antagonists at the V1 receptor, these data suggest that the deaminopenicillamine and, more so, the β-mercapto ββ-cyclopentamethylenepropionic acid residues in position 1 of vasopressin are strong ‘binding elements’ at the V1 vaso pressin receptor but weak ‘binding elements’ at the adenohypophyseal vasopressin receptor. A positive correlation was found between the EC50 values or inhibition constants of the analogues for their effect on β-endorphin release on the on< hand and their potency to displace 3H-arginine vasopressin binding to anterior pituitary membranes on the other hand Therefore, these data support and extend previous suggestions that the structural requirements of the adenohypophysea vasopressin receptor differ from those of the V1 vasopressin receptor. In this sense, the adenohypophyseal vasopressin receptor may represent a novel type of va

ISSN:0028-3835    

DOI:10.1159/000124674

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The concentration of gonadotropin-releasing hormone (GnRH) in the placenta, maternal plasma and fetal hypothalamus was measured in rats during days 13–21 of gestation. A substantial amount of GnRH was detectable in the extract of placenta and maternal plasma samples collected between days 13 and 21 and in the extract of fetal hypothalamus collected between days 19 and 21 of pregnancy. The GnRH level in the placenta and fetal hypothalamus, but not in plasma, fluctuated significantly during pregnancy. The level of GnRH gradually decreased in the placenta but increased in the fetal hypothalamus as the pregnancy proceeded. After gel filtration of placental extract, GnRH eluted in the same position as synthetic GnRH and hypothalamic GnRH. Dilution of placental extracts produced a displacement curve parallel to that of GnRH and hypothalamic extracts. These results indicate that GnRH is present in the placenta and that placental GnRH may have a role in the maintenance of pregnancy in rat

ISSN:0028-3835    

DOI:10.1159/000124675

出版商:S. Karger AG    

年代:1986

数据来源: Karger