In vivo release of endogenous dopamine from rat caudate nucleus by phenylethylamine.

The in vivo release of endogenous dopamine (DA) from the rat caudate nucleus has been measured in the presence and absence of beta-phenylethylamine. A push-pull cannula was implanted into the brain and the tissue was perfused with artificial cerebrospinal fluid (CSF) containing phenylethylamine in concentrations ranging from 5 X 10(-3) to 5 X 10(-7) M. The DA released into the perfusate was determined radioenzymatically. Dopamine was released at rates significantly greater than its resting rate by concentrations of phenylethylamine of 5 X 10(-3) to 5 X 10(-5)M; 5 X 10(-6)M phenylethylamine caused a slight increase in release, but the difference from the resting rate was not significant. The absence of calcium in the perfusing medium did not significantly alter either the unstimulated release rate of DA or the release rate stimulated by 5 X 10(-5)M phenylethylamine. The concentrations of phenylethylamine required to increase release of DA in vivo are discussed briefly in relation to the doses required to elicit behavioural effects.