The ontogeny of amphetamine-induced dopamine release in the caudate-putamen of the rat.

Amphetamine-induced dopamine (DA) release in the caudate-putamen of adult rats was compared with that in the 35-36-day-old and 21-22-day-old rat pup, using in vivo voltammetry. In the adult and 35-36-day groups, 1.0 mg/kg amphetamine (AMP) produced a significant increase in DA release, while 0.1 mg/kg produced no significant change in DA release. In the 21-22-day group, 1.0 mg/kg AMP produced a slight increase, followed immediately by a significant decrease in DA release. Similarly, at a dose of 0.1 mg/kg, AMP produced a significant decrease in DA release. This decrease was greater than that seen after the 1.0 mg/kg dose of AMP. Tyramine produced no significant change in DA release, however, it served as a control for peripheral cardiovascular effects. These data suggest that AMP-induced DA release in the caudate-putamen is mature by postnatal day 35. The AMP-induced decrease in DA release found in the 21-22-day group is not due to either the cardiovascular effects of AMP or to a depletion of DA content. This decrease in neostriatal DA release may be due to a decrease in the neuronal firing of nigrostriatal DA neurons that is caused by an AMP-induced increase in dendritic DA release in the substantia nigra, exerting an inhibitory effect through DA autoreceptors.