Evaluation of the effect of drugs on dopamine metabolism in the rat superior cervical ganglion by HPLC with electrochemical detection.

Drugs known to affect central dopamine turnover, were investigated for their effects on dopamine metabolism in the rat superior cervical ganglion (SCG). A highly sensitive method (fmol range) for the determination of dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) based on isolation on Sephadex columns in combination with high performance liquid chromatography (HPLC) with electrochemical detection, has been developed. The rate of formation of dopamine as well as of DOPAC was determined by monoamine oxidase inhibition. The calculated rate of formation for dopamine was: 250 pmol/ganglion/h, and for DOPAC: 289 pmol/ganglion/h. (+)-Amphetamine, apomorphine as well as haloperidol induced a decrease in DOPAC concentration in the SCG. The effect of haloperidol lasted for at least 8 h. The DOPAC concentrations indicated that chloral hydrate anesthesia markedly inhibited the activity of dopaminergic neurons in the SCG. These observations strongly suggest that the interaction between postsynaptic receptor blockade and the release of dopamine differs in the SCG and in central dopamine receptors.