In the present experiment we tested the effects of L-DOPA and amphetamine upon dopamine and DOPAC efflux in vitro from superfused corpus striatal tissue fragments of male rats who had been pretreated with reserpine. Male rats were treated with reserpine (5 mg/kg) or its vehicle at 24 hours prior to sacrifice and superfusion of the corpus striatum. Two different modes of L-DOPA (5 microM) and amphetamine (10 microM) stimulation, a brief 10-minute and a continuous 60-minute infusion, were tested for their ability to evoke striatal dopamine and DOPAC efflux. Depletion of monoamine storage capacity as achieved with reserpine significantly reduced the amount of basal dopamine and DOPAC released from superfused striatal tissue fragments of male rats. Although basal release rates were significantly reduced, the amount of dopamine and DOPAC released in response to in vitro L-DOPA infusions (10 or 60 minute infusions) was equivalent between reserpine and vehicle treated animals. In contrast, amphetamine stimulated DA release was significantly reduced in male rats treated with reserpine. For both L-DOPA and amphetamine, significantly greater amounts of dopamine were obtained with the 60- versus 10-minute infusion modes. These results demonstrate that the capacity for L-DOPA, but not amphetamine, to evoke dopamine efflux is unaltered under conditions when monoamine storage ability is diminished.

In the present report we examined the effects of estrogen upon catecholamine release from superfused medial basal hypothalamic tissue fragments of pre-pubertal ovariectomized CD-1 mice. Prepubertal mice treated with estradiol benzoate (EB--5 micrograms x 2 days, sc), showed significantly reduced amounts of dopamine but no changes in norepinephrine release in response to a depolarizing concentration of potassium (30 mmol/L) compared with their respective groups receiving the oil vehicle. Since EB treatment reduced potassium stimulated dopamine release in these pre-pubertal mice, in a second experiment we compared the effects of EB versus oil vehicle treatment upon potassium stimulated dopamine release from the hypothalamus of the ovariectomized adult female mouse. Similar to that observed in the pre-pubertal mouse, EB treatment significantly reduced the amount of potassium stimulated dopamine release. Interestingly, the absolute amounts of potassium stimulated dopamine release was substantially greater in adult compared with pre-pubertal mice. These results demonstrate that the hypothalamic dopaminergic system of both pre-pubertal and adult mice show relatively similar responses to estrogen treatment but differ in absolute amounts of dopamine released.