摘要:

Lower concentrations of immunoreactive (IR) β-endorphin were present in the neurointermediate pituitary lobes of streptozotocin-induced diabetic versus control animals at both 2 and 4 weeks after the onset of diabetes. The forms of β-endorphin-like material present appeared to be similar in both groups when studied with cation-exchange chromatography. Insulin therapy via minipump for 2 weeks did not alter this finding of lowered β-endorphin concentrations in diabetic animals, despite normalization of blood glucose levels and body weight gain. Lower IR β-endorphin levels were also found in neurointermediate lobes of weight-restricted rats, but this group had increased plasma IR β-endorphin concentrations compared to diabetic animals. Concentrations of IR β-endorphin in microdissected brain regions and in anterior pituitaries of the diabetic animals failed to show consistent changes; in addition, ACTH concentrations in pituitary lobes and plasma did not differ among groups. Circadian rhythmicity of plasma insulin and corticosterone concentrations was absent in the diabetic animals, although food and water intake, while elevated, showed the normal nocturnal pattern of increased ingestion. Furthermore, adrenal hypertrophy was present in the diabetic animals and was accompanied by an elevation of mean plasma corticosterone levels. The present findings indicate that diabetes is associated with a decrease of neurointermediate pituitary lobe synthesis of β-endorphin, while not affecting the processing of the peptide in this lobe, and confirm previous reports of altered adrenal function in diabetic a

ISSN:0028-3835    

DOI:10.1159/000124155

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

These experiments were conducted sequentially in two parts. In the first, we examined the effect of frontal hypothalamic deafferentation (FHD) on photoperiod-induced changes in luteinizing hormone (LH) concentration in ovariectomized ewes (‘steroid-independent’ changes). In the second we placed Silastic implants of estradiol-17β in these same ewes and examined the effect of FHD on photoperiod-induced changes in the LH concentration in the presence of estradiol (‘steroid-dependent’ changes). 15 ovariectomized Suffolk ewes were subjected either to FHD (n = 10) or sham FHD (n = 5). They were placed in a photochamber and exposed to the following lighting regimens. In the first part, two trials of alternating lighting periods were used: trial 1 = 120 days of 8 h light (L):I6 h dark (D) followed by 90 days of l6L:8D; trial 2 = 90 days of 8L:I6D followed by 60 days of l6L:8D. In the second part, three lighting periods of alternating daylengths were used: 65 days of l6L:8D, followed by 60 days of 8L:I6D and by 60 days of l6L:8D. Blood samples were collected from the jugular vein at 20-min intervals for 3 or 4 h during the last day of each lighting period. Data on mean LH concentrations were obtained. The location of the FHD was verified histologically. In the absence of gonadal steroids, l6L:8D increased, whereas 8L:I6D decreased the LH concentration (p < 0.001) in both sham FHD and FHD ewes. In the presence of estradiol, the LH concentration in sham FHD ewes was 1.53 ± 0.94 ng/ml under l6L:8D, increased to 6.89 ± 4.04 under 8L:I6D, and returned to 0.72 ± 0.14 ng/ml under l6L:8D. In contrast, the LH concentration in FHD ewes was 1.45 ± 0.28 ng/ml under l6L:8D, decreased to 0.82 ± 0.17 under 8L:I6D, and further decreased to 0.54 ± 0.02 ng/ml under l6L:8D. These findings suggest that disruption of the direct neural connections between the anterior and mediobasal hypothalamus did not disrupt steroid-independent photoperiod-induced changes of the LH concentration, but prevented estrogen-dependent photoperiod-induced changes of the LH concentration. These results suggest that direct neural pathways between the anterior and mediobasal hypothalamus are essential for normal photoperiod-induced changes in LH secretion in the ewe and are compatible with hypothesis that the neural pathways which mediate steroid-independent and steroid-dependent changes may no

ISSN:0028-3835    

DOI:10.1159/000124156

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Adenohypophyseal fragments from 8 rats were perifused in small 0.2-ml chambers with medium alone or with medium containing 0.2 or 2 µg/dl T3 or 20 µg/dl T4. The TSH secretion in response to 1-min perifusion with 3 × 10–8M TRH was measured before and at 20- to 40-min intervals after beginning T4 or T3 perifusions. A similar temporal course of inhibition of TRH-induced TSH secretion was produced by both iodothyronines, suggesting but not proving that T4 may inhibit the TSH secretion by a direct effect not dependent on its prior intra- or extrapituitary conversion t

ISSN:0028-3835    

DOI:10.1159/000124157

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

This study was designed to correlate the endocrine responses elicited by acute ether stress with the changes in metabolism of several monoamines in discrete nuclei of the rat brain. Concentrations of norepinephrine (NE), dopamine (DA), and 5-hydroxytryptamine (5-HT) and also of the specific metabolites of NE, DA, and 5-HT, 3-methoxy-4-hydroxyphenylethylene glycol, 3,4-dihydroxyphenylacetic acid, and 5-hydroxyindole-3-acetic acid, respectively, were concurrently measured in microdissected nuclei using high-performance liquid chromatography with electrochemical detection. The ratio of the metabolites to their respective amines was used as an estimate of the metabolism of NE, DA, and 5-HT. Acute exposure to ether vapors induced, within 5–15 min, large increments in plasma levels of adrenocorticotropic hormone (ACTH), β-endorphin, and prolactin (PRL), and decrements in the levels of plasma growth hormone (GH). Significant increases in NE metabolism were observed in the rostral (ANr) and caudal (ANC) divisions of the arcuate nucleus, as well as in the paraventricular (PVN) and dorsomedial nuclei, 15 min after ether stress. A significant decrease in 5-HT metabolism was observed in the PVN, supraoptic nucleus, and ANC, whereas significant increases in 5-HT metabolism were detected in the suprachiasmatic nucleus and ANr. DA metabolism selectively increased in the ANr. The present results indicate that the acute changes in ACTH, β-endorphin, PRL, and GH release induced by ether exposure are temporally correlated with (1) increases in NE metabolism in many hypothalamic nuclei; (2) a selective increase in DA metabolism restricted to the ANr, and (3) differential effects on 5-HT metabolism, probably reflecting selective activation or inhibition of different populations of 5-HT neur

ISSN:0028-3835    

DOI:10.1159/000124158

出版商:S. Karger AG    

年代:1985

数据来源: Karger