Acetylcholine release from guinea pig caudate slices evoked by phorbol ester and calcium

Abstract

In guinea pig caudate slices preloaded with [³H]choline, superfusion with medium containing Ca²⁺ and the phorbol ester TPA (12‐O‐tetradecanoyl phorbol 13‐acetate) produced an increase in the Ca²⁺‐dependent, depolarization‐evoked Ca²⁺ influx. The effect of TPA was antagonized by polymyxin B and H‐7, both inhibitors of protein kinase C. The combination of TPA and calcium ionophore (A23187) provoked the release of ACh to a level equal to the maximal response induced by depolarizing stimuli. TPA alone had no significant effect on the release of ACh. These results suggest that protein kinase C probably plays a role in transmembrane signal transduction involved in the release of neurotransmitter from nerve terminals in the brain.