Alterations in Ca²⁺-dependent and Ca²⁺-independent release of catecholamines in preparations of rat brain produced by ethanol treatment in vivo

Compared to preparations from control animals, superfused striatal slice preparations from brains of rats treated chronically with ethanol released a significantly greater fraction of stored [³H] dopamine on depolarisation in 40 mM K⁺. Similarly, the electrically-evoked release of [³H]-norepinephrine from cortical slices and of [³H]-dopamine from striatal slices is also increased, although with this mechanism of depolarisation the change is significant only in the case of [³H] norepinephrine release. In contrast to this tendency to enhancement of Ca²⁺-dependent depolarisation-induced release, a reduced fraction of stored [³H]-catecholamines was released from these preparations by the indirect sympathomimetics tyramine and (+)-amphetamine. The catecholamine release induced by these indirect sympathomimetics is largely independent of external Ca²⁺ and the results are interpreted as suggesting that chronic alcohol treatment changes the distribution of catecholamine neurotransmitters between storage pools in the nerve terminal which do or do not require Ca²⁺ entry for release.