Progesterone enhances L-dopa-stimulated dopamine release from the caudate nucleus of freely behaving ovariectomized-estrogen-primed rats.
In the present experiment we examined the effect of progesterone upon dopamine (DA) release induced by a direct infusion of unlabeled L-dihydroxyphenylalanine (L-DOPA) into the caudate nucleus of freely behaving rats. Ovariectomized rats were implanted with a push-pull cannula directed at the caudate nucleus and subjected to perfusion under 3 different hormonal conditions: (1) following 4 days of treatment with estradiol benzoate (EB), (2) following 4 days of treatment with estradiol benzoate plus progesterone at 4-6 h prior to perfusion (EB + P-4-6 h) and (3) following 4 days of treatment with estradiol benzoate plus progesterone at 28 h prior to perfusion (EB + P-28 h). During each perfusion session and under each of the 3 hormonal treatment conditions, L-DOPA was infused through the push side of the cannula. Three increasing doses of L-DOPA (10(-6), 10(-5) and 10(-4) M) were infused with a 45-75 min interval between infusions. Regardless of hormonal treatment condition, a clear dose-response increase in DA and 3,4-dihydroxyphenylacetic acid (DOPAC), but not 5-HIAA, output was observed in response to the increasing doses of L-DOPA infusion. For each of the 3 doses of L-DOPA, maximal DA output was observed for animals tested under the EB + P-4-6 h hormonal condition, with statistically significant differences in the areas under the L-DOPA-stimulated DA response curves obtained following the 10(-6) and 10(-5) M doses of L-DOPA infusion.(ABSTRACT TRUNCATED AT 250 WORDS)
Dluzen
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Department of Physiology and Biophysics, University of Illinois, Urbana 61801.
Ramirez
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D000818:Animals; D002421:Caudate Nucleus / Q000187:drug effects / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D007980:Levodopa / Q000494:pharmacology*; D010052:Ovariectomy; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats
D007980:Levodopa; D011374:Progesterone; D004958:Estradiol; D004298:Dopamine