Amphetamine-stimulated release of endogenous dopamine from the rat caudate nucleus in vivo

The in vivo release of endogenous dopamine (DA) has been measured from the rat caudate nucleus. A push-pull cannula was implanted into the brain and the tissue was perfused with artificial cerebrospinal fluid (CSF) containing amphetamine in concentrations ranging from 5 X 10(-3) to 5 X 10(-7) M. The DA released into the perfusate was determined by a radioenzymatic procedure. DA release was increased to levels significantly above its resting rate by amphetamine concentrations of 5 X 10(-6) M or greater. Release stimulated by 5 X 10(-5) M amphetamine was significantly reduced by removing calcium from the perfusing fluid; the unstimulated release rate was not significantly affected. The concentrations of amphetamine required to increase DA release in vivo would appear to be similar to those found in the brain following intraperitoneal doses which produce increases in locomotor activity and stereotyped behavior.