Biochemical and behavioral evidence for an interaction between ethanol and calcium channel antagonists

In the present series of experiments we have studied the effects of the dihydropyridine calcium channel antagonist nifedipine on ethanol-induced changes in behavior and dopamine (DA) release and metabolism. The locomotor-stimulatory effect of low doses of ethanol (2.5 g/kg) was antagonized by nifedipine, whereas ethanol-induced sedation observed after higher doses (4.5 g/kg) was potentiated. Biochemical studies indicated that ethanol enhanced the metabolism and release of DA in the striatum and the DA-rich limbic regions measured by post mortem analyses of DA-metabolites by HPLC with electrochemical detection and by in vivo voltammetry in anaesthetized rats, respectively. Pretreatment with nifedipine antagonized the stimulatory effects of ethanol on the DA-system. Nifedipine reduced the preference for ethanol, estimated by the relative intake of ethanol (6% v/v) and water in a free-choice situation, suggesting an influence of nifedipine not only on the stimulatory but also on the positive reinforcing effects of ethanol. The present results suggest that the locomotor-stimulatory and positive reinforcing effects of ethanol as well as its enhancing effect on dopaminergic activity may involve an enhancement of calcium mediated mechanisms.