摘要:

The effects of abdominal vagotomy at proestrus on ovarian weight and antral follicles greater than 150 µm diameter and on serum levels of gonadotropins and testosterone were assessed 24 and 48 h and 4 and 8 days after surgery. Serum levels of estradiol were assessed at 4 and 8 days. Vagotomy (1) increased ovarian weight at 48 h, decreased ovarian weight at 4 days, but had no effect by day 8. (2) Vagotomy increased healthy antral follicles 151–394 µm diameter at 24 and 48 h and increased atresia in this size range at 4 and 8 days. (3) Vagotomy decreased healthy follicles 151–394 µm at day 8. (4) Vagotomy decreased healthy follicles 395–570 µm at 24 h and decreased atretic follicles at 48 h. (5) Vagotomy decreased the largest (over 570 µm diameter) healthy follicles at 24 h and 8 days. (6) Vagotomy decreased basal serum LH levels at 48 h and 8 days. (In contrast, vagotomy increased FSH at 24 h). There was no effect on blood levels of estradiol and testosterone. These findings are discussed in relation to the hypothesis that the vagus nerve is a component of the hypothalamohy-pophyseal-ov

ISSN:0028-3835    

DOI:10.1159/000124486

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The role of oxytocin (OT) in regulating stress-induced ACTH secretion was investigated by immunoneutralization of endogenous OT with an antiserum raised against synthetic OT. Rats were subjected to one of three stresses: novel environment, tail-hang, or ether. In otherwise untreated rats, ACTH levels rose at least 3-fold in response to all three stresses whereas OT levels increased only in response to tail-hang and ether. Injection of a highly specific antiserum to OT 60 min before the experiment inhibited the ACTH response to tail-hang and ether by 64 and 56%, respectively, but had no effect on the ACTH response to novel environment stress. The data support a physiologic role for OT in the control of ACTH secretion but suggest that it is not until OT levels rise in response to stress that the effects of OT are expressed.

ISSN:0028-3835    

DOI:10.1159/000124487

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Hypothalamic tissue contains TSH-like material which is biologically, immunologically, and physicochemically similar to pituitary TSH. Immunoreactive thyroid-stimulating hormone (IR-TSH) is released from hypothalamic tissue in vitro by depolarizing concentrations of potassium or veratridine by a calcium-dependent mechanism. In the present study, we investigated the subcellular localization of IR-TSH using equilibrium density centrifugation. Tissue homogenates from intact, hypophysectomized or thyroidectomized rats were centrifuged at 150 g at 4°C for 10 min and the supernatants were layered onto continuous sucrose gradients (1.00–1.27 g/ml) and centrifuged at 100,000 g (max) for 16 h. IR-TSH in pituitary supernatants from intact and thyroidectomized rats showed high equilibrium density peaks with a modal density around 1.2 g/ml. Fractionation of the supernatant from ventral or dorsal hypothalamic homogenates resulted in abimodal distribution of IR-TSH. In supernatants from both tissues, IR-TSH containing particles were found at the top of the gradient in a low equilibrium density peak between 1.0 and 1.08 g/ml. In addition, IR-TSH containing particles were found in ventral and dorsal hypothalamic supernatants with modal densities at 1.16 and 1.25, respectively. These high density IR-TSH particles were present in tissue taken from hypophysectomized rats, and were not appreciably affected by thyroidectomy. Homogenization of the tissue in a hypo-osmotic medium disrupted the high density IR-TSH particles resulting in a single low density peak at the top of the gradient. These data suggest that hypothalamic IR-TSH is stored in membrane bound particles which have densities similar to that of secretory granul

ISSN:0028-3835    

DOI:10.1159/000124488

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The effects of corticotropin-releasing factor (CRF) and growth hormone-releasing factor (GRF) on electroencephalograpic (EEG) and behavioral signs of sleep and wakefulness following intracerebroventricular (ICV) administration was investigated in adult male rats. Visual scoring of EEG records as well as spectral analysis revealed that CRF (0.0015–0.015 nmol) produced decreases in slow wave sleep concomitant with significant decreases in spectral power in lower frequencies (1–6 Hz) and increases in high frequencies (32–64 Hz). In contrast, GRF (2.0 nmol) produced increased EEG and behavioral signs of slow wave sleep associated with significant increases in spectral power in the low frequencies (1–2 Hz) and decreases in high frequencies (32–64 Hz). ICV administration of GRF was also found to produce decreases in locomotion when administered during the active part of the rats’ circadian cycle. These EEG and behavioral findings seen following CRF and GRF are consistent with the behaviors frequently correlated with the known circadian timing of the release of corticosteroids and growth hormone during the sleep-waking cycle in ra

ISSN:0028-3835    

DOI:10.1159/000124489

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

We have investigated the effects of intravenous administration of a low dose of dopamine (DA) on plasma growth hormone (GH) concentrations in acromegalic patients and normal subjects with the aim of defining the somatotroph responsiveness to peripheral (i.e., outside the blood-brain barrier) specific dopaminergic stimuli. DA (0.02 µg/kg/ min) was infused for 180 min into 12 acromegalic patients and 10 normal subjects. DA infusion discriminated between two groups of acromegalics. In group I (n = 7), the elevated plasma GH levels (64.1 ± 29.9 ng/ml, mean basal value ± SEM) decreased significantly (mean overall GH inhibition, 26% reduction from basal levels; range, 10–49), whereas in group II (n = 5) plasma GH levels (29.8 ± 12.5 ng/ml) remained elevated (mean GH variation, 8% above baseline; range, 0–15). Plasma GH concentrations showed a significant rebound above baseline values after stopping DA infusion only in group I. In contrast, the responsiveness to TRH was not significantly different between the groups (percentage increase 767 ± 317% in group I vs. 382 ± 210% in group II) and they were also comparable with regard to sex, age, glucose tolerance, plasma prolactin (PRL) concentrations and adenoma size. However, the mean duration of the disease was significantly (p < 0.02) longer in group I (12.8 ± 2.6 years) than in group II (4.5 ± 1.5 years). Further, 3 patients with previous radiotherapy for invasive adenomas were nonresponders to DA. In normal subjects, DA infusion had no significant effect on plasma GH levels. It is concluded that: (1) somatotroph responsiveness to DA is not a constant feature of acromegaly. This responsiveness may be selectively altered in the cases of invasive and irradiated adenomas. (2) Peripheral specific DA stimuli does not increase GH release in

ISSN:0028-3835    

DOI:10.1159/000124490

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Release of vasopressin (AVP) and oxytocin (OT) from rat median eminence and posterior pituitary tissue was studied in vitro by incubation in Krebs-56 mM KCl buffer. Both total tissue content and releasable pool of each hormone was measured in control rats, adrenalectomized rats and dexamethasone-treated rats. Adrenalectomy resulted in significantly increased release of AVP, but not OT, from median eminence tissue, whereas dexamethasone treatment failed to affect release of either hormone. Neither treatment had any effect on AVP or OT release from posterior pituitary tissue. Similarly, neither treatment caused any significant changes in total median eminence or posterior pituitary AVP and OT contents relative to controls, although dexamethasone-treated rats had a significantly lower posterior pituitary OT content than adrenalectomized rats. KCl-stimulated hormone release from median eminence tissue most likely represents an estimate of AVP and OT in zona externa terminals rather than in zona interna axons, because release was blocked by CoCl2 indicating calcium-dependent exocytosis. Immunohistochemical staining of median eminence tissue correlated well with the results of in vitro hormone release, in that increased AVP staining in the zona externa of adrenalectomized rats was also the only significant change noted using this methodology. Since increased levels of releasable AVP in the median eminence probably reflects similarly increased AVP levels in the hypothalamo-hypophyseal portal vessels of adrenalectomized rats, these results support a potential physiologic role for median eminence AVP, but not OT, in the chronic stimulation of adrenocorticotropin hormone secretion following adrenalectomy.

ISSN:0028-3835    

DOI:10.1159/000124491

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

In female golden hamsters, vomeronasal organ removal disrupts the elicitation of lordosis by lumbosacral tactile stimulation. A similar disruption occurs if the nasopalatine ducts are closed, without removing the vomeronasal organ. Injection of luteinising hormone-releasing hormone reverses the effect of vomeronasal organ removal. These findings suggest that chemosensory signals from the male hamster act via the accessory olfactory system, to facilitate the triggering of lordosis by somatic stimulation.

ISSN:0028-3835    

DOI:10.1159/000124492

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The effect of estrogen on prolactin (PRL) synthesis at a single-cell level was studied by in situ hybridization and immunohistochemistry. Long-term estrogen treatment increased PRL-containing cells from 10–20% of total cell population to 80–90%, as revealed by immunohistochemistry. PRL mRNA containing cells also increased in a similar fashion. Moreover, cytoplasmic PRL mRNA expressed as the number of silver grains per cell increased 4- to 5-fold by estrogen. These results suggest that long-term estrogen treatment causes not only PRL cell proliferation but also an increase in PRL mRNA in a single c

ISSN:0028-3835    

DOI:10.1159/000124493

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Male Syrian hamsters were kept under either 14 h light/10 h dark (lights on at 06.30 h) or 2 h light/22 h dark (lights on at 14.30 h) photoperiods. Groups of hamsters under each photoperiod were rendered hypothyroid by addition of 0.4% thiourea to the drinking water. These hamsters received, in addition, either a daily evening injection of saline or a daily injection of 25 µg melatonin in saline. Groups of intact controls and pinealectomized control hamsters were also maintained under the two photoperiodic conditions. After 10 weeks under the different conditions the hamsters were killed by decapitation, and serum samples assayed for thyroxin, thyroid-stimulating hormone (TSH), and prolactin (PRL). Pituitary extracts were assayed for TSH and PRL. Hypothyroidism in hamsters receiving thiourea was confirmed by radioimmunoassay data showing low serum thyroxin and greatly elevated serum TSH concentrations. Melatonin injections resulted in significant depression of serum TSH in thiourea-treated hamsters under short photoperiod compared to saline-injected controls. Both melatonin injections and short photoperiod resulted in a significant reduction of pituitary TSH in hamsters on thiourea compared to values obtained from similarly treated animals under the 14 h light/10 h dark photoperiod. Hypothalamic concentrations of thyrotropin-releasing hormone (TRH) were significantly elevated by melatonin injections and by short photoperiodic conditions, but not by thiourea administration. The short photoperiod resulted in testicular involution which was completely reversed by pinealectomy and partially reversed (to 53% of controls) by thiourea treatment. Involution of gonads was complete in thiourea-treated animals under short photoperiod, if they received melatonin injections. It is concluded that the inhibitory effect of melatonin on the pituitary-thyroid axis is the result of an inhibition of release of hypothalamic TRH. Since incomplete gonadal involution was observed in hypothyroid hamsters under short photoperiod, the data suggest a thyroxin requirement for complete gonadal involution. The hypothesis that inhibition of both TSH and PRL secretion is the result of decreased release of hypothalamic TRH is discussed

ISSN:0028-3835    

DOI:10.1159/000124494

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

In order to gain additional information on the role played by the opioids in the control of the secretion of anterior pituitary gonadotropins, morphine (an opioid agonist) and naloxone (an opioid antagonist) have been injected intraventricularly (i.v.t.) into normal or castrated male rats. The animals were killed by decapitation at different time intervals after treatment and serum luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin were measured by radioimmunoassay. Animals injected i.v.t. with 0.9% saline solution and sacrificed at the same time intervals served as controls. When morphine (at the dose of 200 and 400 µg/rat) and naloxone (at the dose of 7.5 and 15 µg/rat) were injected i.v.t. into normal male rats, a significant increase of serum levels of LH was observed 10 and 20 min after injection. There was no effect at 5, 40 and 60 min. Lower doses of morphine (6.25, 12.5, 25, 50 and 100 µg/rat) given i.v.t. were ineffective. When morphine (200 µg/rat) and naloxone (either in the dose of 7.5 µg/rat or of 15 µg/rat) were given simultaneously, serum LH was significantly higher than in the saline-treated controls both at 10 and 20 min. However, the increases of serum LH levels induced by the combined treatment were in both instances lower than those produced by the administration of either drug alone. Morphine (200 µg/rat) when administered i.v.t. to normal male rats significantly enhanced prolactin release at 10 and 20 min, and this effect of morphine was blunted by the concomitant i.v.t. administration of naloxone (7.5 and 15µg/rat). Finally morphine, when injected i.v.t. in the dose of 200 µg/rat into male rats castrated 4 weeks before, significantly decreased serum LH levels beginning 40 min after treatment; this effect of morphine lasted up to the last interval of observation (180 min). No one of the subcutaneous or i.v.t. treatments discussed above exerted any consistent effect on serum FSH levels either in normal or castrated male rats. The following conclusions may be drawn from our observations: (1) The stimulatory effect exerted by naloxone given i.v.t. on LH secretion confirms that endogenous opioids exert mainly an inhibitory influence on LH secretion. (2) The stimulatory effect on LH secretion observed following the i.v.t. injection of morphine into normal male rats suggests that opioid pathways (or receptors) influencing in a stimulatory way the mechanisms controlling LH secretion might also exist. (3) The opposite effects exerted by i.v.t. morphine in normal and castrated male rats indicates that the endocrine ‘milieu’ present in the animal at the time of the experiment is crucial in directing the effects exerted by the opioids on LH secretion. (4) The lack of effect of morphine and naloxone on the release of FSH suggests that brain opioids do not participate in the regulation of the release of this gonadotropin. It appears from the data that the mechanisms controlling LH and FSH release are substantial

ISSN:0028-3835    

DOI:10.1159/000124495

出版商:S. Karger AG    

年代:1986

数据来源: Karger