Exp Clin Endocrinol Diabetes 1995; 103(3): 196-204
DOI: 10.1055/s-0029-1211350
Original

© J. A. Barth Verlag in Georg Thieme Verlag KG Stuttgart · New York

Time course of the effects of steroid hormone deprivation elicited by ovariectomy or ovariectomy plus adrenalectomy on the affinity and density of GABA binding sites in distinct rat brain areas

A. Jussofie, I. Körner, C. Schell, C. Hiemke*
  • Institut für Physiologische Chemie, Universitätsklinikum Essen, Germany
  • * Psychiatrische Klinik der Joh.-Gutenberg Universität Mainz, Germany
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Publication History

Publication Date:
15 July 2009 (online)

Summary

The time course of the behaviour of GABAA receptors (affinity of muscimol for GABA binding sites and their number) in membranes obtained from five distinct rat brain areas was evaluated in dependence of the decline of the serum concentrations of estradiol and progesterone following hormone deprivation by either ovariectomy (OVX) or ovary- plus adrenalectomy (OVX-ADX) after 1, 2, 3, 5, 14 and 30 days. Diestrus rats served as control. The effect of OVX on the GABA binding sites was due to a decrease of affinity rather than alterations in their density. Conversely, the combined surgery of OVX plus ADX affected both the affinity and the density. Also, the OVX-linked changes of muscimol binding were observed only after five days as compared to control animals, while the initial OVX-ADX associated changes occurred already after one day. OVX-ADX produced significant decreases in the number of binding sites at the shortest times investigated, in frontal cortex (FC) at day one and two and in the medulla oblongata (MED) after three days, which disappeared in the subsequent times studied. Concomitant with the major decrease of steroid hormone serum levels one day after OVX-ADX the FC displayed an increase in affinity by 45%. From the time when steroid serum levels are low the alterations in affinity elicited by both OVX-ADX and OVX only take a similar course reflected by the following decrease in affinity. In MED an additional adrenalectomy did not significantly modify the OVX linked decrease of affinity, except that the initial effect was already evident two days after OVX-ADX. The cerebellum (CER) displayed an increase of affinity only following OVX-ADX after one and two days, while the affinity determined in the hippocampus (HIP) and hypothalamus (HYP) was not affected by either OVX or OVX-ADX. These findings show that the brain areas investigated behave differently to peripheral steroid hormone deficit and argue strongly in favour of a dual steroid hormone action: The effect of OVX on the GABAA receptor complex may be primarily mediated by an indirect mechanism of steroid action while the effect of an additional ADX seems to include direct steroid actions.

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