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B D Shivers

Publications and source records attributed to B D Shivers.

44 records · Page 3Linked to original sources
PubMed1983

Immunocytochemical localization of luteinizing hormone-releasing hormone in male and female rat brains. Quantitative studies on the effect of gonadal steroids.

The peroxidase-antiperoxidase immunocytochemical method was used to determine quantitatively the effects of gonadal steroids on the immunoreactive luteinizing hormone-releasing hormone (LHRH) content in the brain of male and female rats. In the male rat, gonadectomy decreased both the number of cell bodies and optical density of staining in cell bodies containing immunoreactive LHRH; decreased the percentage of area covered by LHRH fibers in the middle and caudal aspects of the median eminence (ME) but not the organum vasculosum lamina terminalis (OVLT), and decreased the number of LHRH fibers localized in the midbrain central gray (MCG). Since others have shown previously that gonadectomy increases the LHRH content of portal blood in the male rat, the results suggest that the decreased somal accumulation of LHRH and decreased LHRH content in fibers in the ME and MCG measured in the present study following loss of testicular steroids reflect increased LHRH release from the ME and MCG into the portal blood and brain, respectively. Estrogen replacement in the gonadectomized female rat increased the optical density of staining in cell bodies but not the number of cell bodies containing immunoreactive LHRH, increased the percentage of area containing LHRH fibers in the caudal aspect of the ME but not the OVLT, and decreased the number of fibers containing LHRH in the MCG. Since others have shown previously that estrogen replacement to gonadectomized female rats decreases LHRH release into portal blood, the present results suggest that the estrogen-induced increases in somal accumulation of LHRH and increases in LHRH content in fibers in the ME reflect a decreased LHRH release from the ME into the portal blood. By analogous reasoning, the decreased LHRH fiber content measured in the MCG following estrogen replacement to gonadectomized females reflects an increased LHRH release into the MCG. This inference is consistent with a postulated role for LHRH in this brain site in the facilitation of lordotic responsiveness.

Animals↗
PubMed1982

Intrahypothalamic colchicine infusions disrupt lordotic responsiveness in estrogen-treated female rats.

Since some estrogenic effects on lordotic responsiveness are mediated through hypothalamic protein synthesis, we conducted experiments to determine if axoplasmic transport in the hypothalamus is necessary for the induction and maintenance of this reflex by estrogen. Colchicine infusion into the hypothalamus, but not into the dorsal thalamus, of ovariectomized rats 24 h prior to administration of subcutaneous estrogen implants delayed the induction of lordotic responsiveness, as measured by the manual (cutaneous-pressure) method, by 2 days, as compared with vehicle-infused rats. In other experiments, colchicine infusion into the hypothalamus, but not into the dorsal thalamus, of conscious, ovariectomized, estrogen-implanted rats displaying maximal lordotic responsiveness resulted in a bimodal decline in lordotic responsiveness. An initial decline occurred 20-40 min after infusion, and was associated with general behavioral agitation and hyperactivity. A subsequent decline began 4 h after infusion and lasted for several days. Vehicle infusion did not decrease lordotic responsiveness. Colchicine infusion did not alter multiunit electrical activity recorded near hypothalamically directed cannulae tips over a period of several hours. Results suggest that axoplasmic transport within and/or from the hypothalamus is necessary for the estrogenic induction and maintenance of the lordosis reflex in rats.

Animals↗
PubMedDate not supplied

Failure of urethane anesthetic to block induction of pineal serotonin N-acetyltransferase activity in the rat.

Ability of urethane anesthetic to block induction of pineal serotonin N-acetyltransferase (SNAT; E.C.2.3.1.5) activity was measured in individual rat pineal glands in animals receiving urethane (25% w/v, IP, 1.2 g/kg) or saline, 6 hr prior to sacrifice. Using a radioenzymatic assay, SNAT determinations were made twice daily (at 1200 or 2400 hr) immediately after the sacrifice of each animal. The results show that urethane had no effect on the induction of SNAT activity: (1) implying that the neural activity of those structures involved in induction of SNAT activity (e.g., suprachiasmatic nucleus) is not substantially altered by this anesthetic and (2) suggesting that the central blockade of ovulation by urethane does not include alterations in suprachiasmatic nucleus activity.

Acetyltransferases↗
PubMedDate not supplied

Absence of oestradiol concentration in cell nuclei of LHRH-immunoreactive neurones.

Oestrogen, acting in both the brain and pituitary, has a critical role in regulating the reproductive cycle in most mammals. In the brain, oestrogen regulates the release of luteinizing hormone-releasing hormone (LHRH) partly through a mechanism that is blocked by inhibitors of DNA-dependent RNA synthesis or protein synthesis. The distributions of oestrogen-concentrating neurones and of LHRH neurones overlap. The present study was undertaken to determine whether genomic effects of oestrogen mediated by nuclear oestradiol concentration include a direct effect on LHRH-containing neurones. During extensive studies in which the immunocytochemical method for localizing LHRH neurones was optimized and made compatible with the autoradiographic method for detecting oestrogen-concentrating neurones, doubly-labelled cells were very rarely seen. This suggests that genomic regulatory effects of oestrogen which depend on nuclear retention are not exerted directly on most LHRH neurones, but rather must be mediated by another class of neurones.

Animals↗