Effects of apamin on the discharge properties of putative dopamine-containing neurons in vitro.

An in vitro brain slice preparation was used to evaluate the effects of apamin, a selective inhibitor of calcium-activated potassium channels, on the discharge characteristics of presumed dopamine-containing neurons within the substantia nigra. Apamin administration (1 microM) was associated with an increase in neuronal excitability as evidenced by the emergence of both sustained irregular and intermittent bursting activity similar to that seen spontaneously in vivo. These data suggest that the characteristic regular activity observed among putative dopamine-containing neurons in vitro is mediated, in part, by a calcium-activated potassium conductance.