Attenuation of Pilocarpine-Induced Drinking By Chronic Treatment with Estrogens

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Abstract
Acute i.p. administration of graded doses of the parasympathomimetic agent, pilocarpine, to female rats increased their water intake, urine output and urinary Na excretion rate in a graded fashion. Of the 3 responses, urine output and urinary Na excretion rate increased on administration of a dose of pilocarpine that had minimal effect on water intake. Chronic treatment of female rats with estradiol benzoate (21 and 42 .mu.g/kg per day) or estradiol-17.beta. (6.5 and 16.5 .mu.g/kg per day) attenuated significantly the drinking response to pilocarpine (3 mg/kg i.p.) but failed to affect the increase in urine output or urinary N2 excretion rate. The mechanism by which chronic treatment with estrogens attenuates pilocarpine-induced water intake is unknown and awaits additional study.