摘要:

Catecholamines were measured in the separated intermediate and posterior lobes of the rat after stalk section and bilateral superior cervical ganghonectomy. In the intermeiate lobe, after stalk section, dopamine decreases 96%, norepinephrine decreases 80%, and epinephrine is undetectable. In the posterior lobe, dopamine and epinephrine are absent, and norepinephrine decreases by 70% after the operation. In contrast, bilateral superior cervical ganghonectomy produces only a 40% decrease in norepinephrine in the posterior lobe, and no changes in catecholamines in the intermediate lobe. Our results demonstrate that most of the intermediate and posterior pituitary catecholamines are present in nerve fibers of brain origin, and that the posterior lobe has a dual norepinephrine innervation, partly originating in the superior cervical ganglia.

ISSN:0028-3835    

DOI:10.1159/000124087

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Olfactory bulbectomy unmasks photoperiodic responsiveness in normally nonphotoperiodic rats. We assessed whether the photoperiodic effects of bulbectomy reflect disruption of chemosensory input. At 26–28 days of age, male Sprague-Dawley rats were subjected to removal of their vomeronasal organ (VNO) complex, a sham-VNO ablation or large electrolytic lesions aimed at the pyriform cortex or corticomedial nuclei of the amygdala. Other rats were infused with (1) 7.5% ZnSO4, a treatment that destroys the olfactory neuroepithelium, (2) 0.09% saline, or (3) air in each external nare every 4 days; rats from each treatment condition were assigned either to a long (LD 14:10) or short (LD 8:16) day lighting regimen and were autopsied at 90 days of age. Seminal vesicle and paired testes weights did not differ significantly among long-day groups. Mean seminal vesicle and paired testes weights were decreased only in short-day rats treated with ZnSO4. These results indicate that the VNO does not mediate the effects of photoperiod on rat reproduction. Olfactory information, not transduced by the amygdala, or nonsensory components of the olfactory bulbs appear to mask photoperiodism in intact rat

ISSN:0028-3835    

DOI:10.1159/000124088

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

To assess the role of peripheral sympathetic nerves in the regulation of parathyroid hormone (PTH) release rats subjected to bilateral superior cervical ganglionectomy (SCGx) 8–24 h earlier were used. SCGx did not result in significant changes of basal serum calcium (Ca) or immunoreactive PTH (iPTH) levels. The i.p. administration of EDTA every 30 min for up to 3 h brought about an impending decrease of serum Ca levels in both sham-operated and SCGx rats when assessed 23 h after surgery. The extent of hypocalcemia was significantly larger in the SCGx group. In sham-operated controls serum iPTH increased by 32–145%, 1–3 h after beginning EDTA treatment whereas such increases were considerably lower or absent in SCGx rats. In 3 out of 7 SCGx animals that survived to a double EDTA dose, iPTH increased to levels indistinguishable from controls. When SCGx rats subjected to surgery 23 h earlier and receiving d-l-propranolol (5 mg/kg) or phentolamine (10 mg/kg) 4 h and 30 min earlier were submitted to iterative EDTA injection serum iPTH increased, whereas no changes were detected in SCGx rats treated with vehicle and subjected to the same EDTA treatment. These data indicate that (1) SCGx does not affect basal release of iPTH or serum Ca concentration; (2) 23–26 h after SCGx there is a significant impairment of homeostatic iPTH responses to low Ca levels which can be overcome by suitable Ca stimulus; (3) circulating catecholamines may affect denervated parathyroid cells, as revealed by the changes in serum iPTH and Ca elicited by α- and β-adrenoceptor-blocker treatment of

ISSN:0028-3835    

DOI:10.1159/000124089

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

These studies were designed to: (1) determine the effects of continuous infusion of synthetic ACTH (1–24) on postcastration changes in serum and pituitary LH, FSH and prolactin in the male rat; (2) assess the effects of adrenalectomy on the gonadotropin and prolactin response to ACTH, and (3) test the hypothesis that ACTH may directly (not via adrenal factors) alter gonadotropin secretion at the brain and/or pituitary level. Adult male rats were either orchidectomized (ORX) or orchidectomized-adrenalectomized (ORX-ADX), and were treated continuously for 6 days with ACTH (1–24) (10 µg/day) or saline using an osmotic minipump. Animals were killed on day 6 following castration. ACTH treatment reduced serum LH and prolactin levels in ORX rats to mean values ± SE of 204 ± 25 and 37 ± 3 ng/ml respectively, compared to 366 ± 72 and 62 ± 7 ng/ml in saline-treated ORX animals. Serum FSH concentrations were not altered by ACTH administration. Pituitary concentrations of LH and FSH, but not prolactin were enhanced by ACTH treatment. Adrenalectomy had no effect on serum and pituitary gonadotropin and prolactin levels, but abolished the effects of ACTH on these parameters. Central (intracerebroventricular) infusion of ACTH (1–24) (6 µg/day × 4 days) failed to alter the rise in serum LH in male rats following orchidectomy. Acute treatment with large doses of ACTH of perifused anterior pituitary glands from male rats and chronic treatment with ACTH of enzymatically dispersed anterior pituitary cells from female rats did not influence basal or GnRH-stimulated LH secretion. Our results suggest that in the male rat ACTH retards LH secretion via unknown adrenal factors. We were unable to find any evidence that ACTH per se is capable of directly modulating gonadotropin secretion at either the brain or pi

ISSN:0028-3835    

DOI:10.1159/000124090

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The effects of morphine (10 mg i.v.), an opioid agonist, and of naloxone (10 mg i.v.), an opioid antagonist, on serum levels of TSH and PRL were studied in 7 hypothyroid patients and in 5 normal volunteers. Morphine administration induced a prompt, significant increase in serum TSH and PRL in all subjects. The degree of PRL release after morphine was similar in the two groups, while, as regards TSH, the increase was more evident in hypothyroid subjects. Pretreatment with naloxone (4 mg i.v. 5 min before morphine administration) blocked these effects in all subjects. In contrast, naloxone alone was not able to affect significantly TSH and PRL secretion. Moreover, in 5 other euthyroid volunteers, morphine significantly enhanced the response of TSH and PRL to TRH stimulation (200 µg i.v.)

ISSN:0028-3835    

DOI:10.1159/000124091

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Compensatory thyroid growth in rats subjected to unilateral thyroidectomy (Tx) and superior cervical ganglionectomy (SCGx) performed ipsilaterally to the remaining lobe was about 2-fold that of rats subjected hemiTx alone, when assessed 7–15 days after surgery. HemiTx depressed serum T4 levels by 33% and increased serum TSH by 80% in control rats. Unilateral SCGx, which did not affect circulating T4 or TSH by itself, prevented hemiTx-induced changes of hormone levels. After hypophysectomy (Hpx) thyroid involution ensued. The subsequent hemiTx of Hpx rats did not affect Hpx-induced thyroid regression 7 days later, but abolished it 15 days later. At this time a factorial analysis of variance revealed lack of significant interaction between Hpx and hemiTx thus suggesting that a similar thyroid growth ensues after hemiTx regardless of pituitary intactness. However, both serum T4 and TSH levels were very low in Hpx rats regardless of whether one or two thyroid lobes were present indicating that thyroid growth in the absence of pituitary was not accompanied by increased secretory activity. SCGx performed ipsilaterally to the remaining lobe blunted the growth of the lobe in Hpx hemiTx rats. Moreover, the denervated thyroid lobe regressed in Hpx rats to values significantly lower than those of Hpx rats having intact sympathetic nerves both in the presence or in the absence of a contralateral thyroid lobe. SCGx did not modify the very low serum TSH and T4 levels of Hpx rats. These results indicate that (1) in rats with intact pituitaries ipsilateral SCGx amplifies the compensatory growth and increases T4 secretion of the remaining lobe after hemiTx; (2) in Hpx rats ipsilateral SCGx blunted the growth that follows unilateral Tx and induces further regression of the denervated lobe regardless of whether a contralateral lobe is present or no

ISSN:0028-3835    

DOI:10.1159/000124092

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

This paper presents evidence which demonstrates that a site within the anterior hypothalamus of the Syrian hamster is essential for the expression of a photoperiodic response but not for the expression of oestrous or circadian activity rhythms. Selective lesions of the anterior hypothalamic nucleus (AHN) were produced by localized infusions of n-methyl aspartic acid (NMA). Histological analysis revealed that the suprachiasmatic and paraventricular nuclei were resistant to the toxin. Circadian locomotor activity rhythms and oestrous cyclicity were unaffected by these lesions but the photoperiodic response of the gonads to short day length (8L:16D) was completely prevented. In marked contrast to control animals, lesioned animals maintained large testes or ovulatory ovaries, even after 10 weeks of exposure to the inhibitory photoperiod. These data suggest that neurones within the AHN form an essential component of the photoperiod time-measuring apparatus which is independent of that controlling circadian rhythmicity.

ISSN:0028-3835    

DOI:10.1159/000124093

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Mediobasal hypothalamic (MBH) slices of adult ovariectomized (OVX) rats with or without 17β-estradiol (E2) pretreatment, were superfused in buffered (pH 7.2) oxygenated Locke medium containing bacitracin. Pulsatile or continuous administration of progesterone (10–7 or 10–8M) produced a marked increase in luteinizing hormone-releasing hormone (LHRH) release provided the animals had received E2 prior to sacrifice. Omission of Ca++ in the medium, or addition of a Ca++ channel blocker (D-600, 10–4M), of a calmodulin inhibitor (trifluoperazine, 30 µM) or of a calmodulin-dependent tubulin kinase inhibitor (phenytoin, 50 µM), antagonized the stimulatory effect of progesterone. When sodium channels were blocked by tetrodotoxin (5 × 10–7M), the stimulatory effect of the steroid was completely abolished. The amplitude of the K+-induced LHRH release was slightly increased in the presence of progesterone (10–7M) but only from MBH slices of OVX-E2-treated rats. These results indicate that the secretory response of LHRH to progesterone requires priming with estradiol, is Ca++-dependent and involves mediation of calmodulin and a calmodulin-dependent

ISSN:0028-3835    

DOI:10.1159/000124094

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The relative importance of several phospholipid pathways in cyclic AMP (cAMP) metabolism and growth hormone (GH) release was determined by an indirect, pharmacological approach in cultured anterior pituitary cells. The diglyceride lipase inhibitor RHC-80267 (30–100 µM) had no significant effect on cAMP levels but markedly inhibited basal and growth hormone-releasing factor- (GRF) stimulated GH secretion. A phospholipase A2 inhibitor quinacrine (30 µM) increased cellular cAMP content while decreasing GH release. Indomethacin, which reduces cyclooxygenase activity, affected neither cAMP levels nor GRF-enhanced GH release; this drug (30–100 µM) did reduce basal GH release. The lipoxygenase inhibitors nordihydroguaiaretic acid and BW-755c both reduced basal and GRF-stimulated GH release in a concentration-dependent manner. Both agents had various effects on cAMP levels. These results suggest that phospholipid metabolism, through both the cyclooxygenase and lipoxygenase pathways, contributes to basal GH release, wihle the lipoxygenase route predominates in GRF-stimulated GH release in vitro. Interestingly, cAMP metabolism can be dissociated from GH release with some of these probes, indicating an action of phospholipid metabolites distal or lateral to the cAMP-generating

ISSN:0028-3835    

DOI:10.1159/000124095

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Ultracentrifugation and sucrose gradient separation techniques have been applied to study of the subcellular distribution of hypothalamic luteinizing hormone (LH). Subcellular particle-bound LH accounted for 42% of the total LH while cytoplasm contained 58% of the total immunoassayable LH in these extracts. 70% of particle-bound LH was present in the P2 fraction and most of the particle-associated LH was found in subfractions of P2 rich in synaptosomes but poor in myelin and mitochondria. While actual amounts of LH in the P3 and P4, the microsomal fractions, were relatively small, the concentration of LH, expressed as nanograms per milligram of protein was quite high. Both content and concentration of LH in the nuclear pellet, P1, were substantially lower. These findings provide further framework for speculation on the role of brain-based LH.

ISSN:0028-3835    

DOI:10.1159/000124096

出版商:S. Karger AG    

年代:1985

数据来源: Karger