Dk. Raap et al., Estrogen desensitizes 5-HT1A receptors and reduces levels of G(z), G(i1) and G(i3) proteins in the hypothalamus, NEUROPHARM, 39(10), 2000, pp. 1823-1832
The present study investigated whether estrogen would desensitize hypothala
mic serotonin(1A) (5-HT1A) receptors by examining the neuroendocrine respon
se to 8-OH-DPAT, a 5-HT1A agonist. Rats were ovariectomized, allowed to rec
over for 5 days, then given 2 daily injections of estradiol benzoate or veh
icle (10 mu g/day, s.c.). Twenty-four hours after the second injection, rat
s were challenged with a sub-maximal dose of 8-OH-DPAT (50 mu g/kg, sc) or
saline 15 min prior to sacrifice. 8-OH-DPAT produced a significant increase
in plasma oxytocin, ACTH and corticosterone levels in ovariectomized rats.
While estrogen treatment for 2 days did not alter basal hormone levels, it
did significantly reduce the magnitude of oxytocin, ACTH and corticosteron
e responses to 8-OH-DPAT, The reduction in hormone responses was accompanie
d by a significant reduction in hypothalamic levels of G(z), G(il) and G(i3
) proteins (by 50%, 30% and 50%, respectively). These findings suggest that
a reduction in these G proteins may contribute to the mechanisms underlyin
g estrogen-induced desensitization of 5-HT1A receptors. The desensitization
of 5-HT1A receptors has been suggested to underlie the therapeutic effects
of antidepressant 5-HT uptake inhibitors (SSRIs). Thus, the present result
s suggest that estrogen or estrogen-like substances in combination with SSR
Is may prove effective in developing novel therapeutic strategies for neuro
psychiatric disorders in women. (C) 2000 Elsevier Science Ltd. All rights r
eserved.