Time-dependent effects of ovarian steroids on tyrosine hydroxylase activity in the limbic forebrain of female rats.
In this work, we have studied the time-course of the effects of pharmacological administration of ovarian steroids on tyrosine hydroxylase (TH) activity in the limbic forebrain of ovariectomized rats. Administration of estradiol produced a late decrease in TH activity. This effect was found 24 hours after the last steroid injection, disappearing at 32 hours. It was antagonized by progesterone, since a single injection of this steroid to estradiol-pretreated rats reversed to control values the estradiol-induced decrease. Nevertheless, the administration of progesterone after estradiol treatment caused a short-time decrease in the limbic activity of TH, which was observed 4 hours after the last steroid injection, disappearing subsequently. On the other hand, the administration of progesterone alone produced a biphasic effect, with a reduction at 24 hours, followed by an increase at 32 hours. These effects were only observed in the animals non-treated with estradiol, disappearing with a previous treatment with estrogens. Hence, it can be concluded that both ovarian steroids may affect the limbic TH activity. Thus, estradiol produced a late inhibitory effect on the activity of this enzyme, which was antagonized by progesterone. Administration of the last one to estradiol-treated rats produced a short-time inhibitory effect, whereas its administration to non-treated rats produced a late biphasic effect (inhibition followed by stimulation), which was not observed in estradiol-treated rats.
Hernández
M L
ML
Department of Biochemistry, Faculty of Medicine, Complutense University, Madrid, Spain.
Fernández-Ruiz
J J
JJ
de Miguel
R
R
Ramos
J A
JA
D000818:Animals; D004298:Dopamine / Q000378:metabolism; D004347:Drug Interactions; D004790:Enzyme Induction / Q000187:drug effects; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D008032:Limbic System / Q000187:drug effects* / Q000201:enzymology; D010052:Ovariectomy; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D013997:Time Factors; D014446:Tyrosine 3-Monooxygenase / Q000037:antagonists & inhibitors* / Q000378:metabolism
D011374:Progesterone; D004958:Estradiol; D014446:Tyrosine 3-Monooxygenase; D004298:Dopamine