Abstract
When levodopa (L-DOPA) is administered to mice, the central nervous system responses to the dopamine stimulation were less sensitive in female than in the male mice. The sensitivity is reflected both behaviorally and biochemically. The behavioral response were measured by scores recorded after intraperitoneal injection of a standard dose of L-DOPA. The biochemical studies included the determination of the cyclic AMP produced by in vitro experiments after incubating dopamine with mouse caudate nucleus homogenates. This insensitivity to dopamine stimulation in female animals can be reversed by ovariectomy. Estradiol treatment in vivo suppressed the dopamine stimulation, while estradiol directly added to the caudate nucleus homogenate does not affect the dopamine-sensitive adenylate cyclase activity. These findings indicate that the estradiol-induced effects on the brain enzyme are indirect. The female sex hormone does have an effect on the central dopaminergic system. However, the underlying mechanism(s) cannot be delineated by the present studies.
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