The sialagogue response of striatal dopamine receptors to L-dopa is not influenced by castration or chronic estrogen treatment.
The secretory response of salivary glands to L-dopa, elicited by stimulation of dopamine receptors in the striatum and the circling behavior induced by apomorphine in animals bearing a unilateral kainic lesion of the entopeduncular nucleus, was studied in intact and ovariectomized female rats. Castration did not modify the sialagogue response to L-dopa, while the turning behavior was significantly increased. Daily administration of 17-beta-estradiol benzoate during 7 days to ovariectomized rats decreased the circling activity to the level of intact female rats, while the salivary secretion to L-dopa was unaffected. The above findings suggest that the sialagogue response induced by L-dopa may be due to the interaction of this agonist with D1 striatal receptors, whose activity is not influenced by estrogens. However, we cannot rule out any possible alteration in the metabolism and/or presynaptic conversion of L-dopa to dopamine by estrogen treatment. The changes in turning behavior may be attributed to an antidopaminergic effect of estrogens and/or, like L-dopa, to modifications in the metabolism of apomorphine induced by the hormone.
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism; D003714:Denervation; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D007608:Kainic Acid / Q000494:pharmacology; D007980:Levodopa / Q000494:pharmacology*; D010052:Ovariectomy; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects*; D012469:Salivary Glands / Q000378:metabolism* / Q000503:physiopathology; D013997:Time Factors
D011954:Receptors, Dopamine; D007980:Levodopa; D004958:Estradiol; D007608:Kainic Acid