No abstract

Premcubatlonof intact fetal bram neurons m culture with the phorbol ester TPA (12-0-tetradecanoyl phorbol-13-acetate) m the presence of calcmm, resulted m the enhancement of the depolanzatlon-mduced, Ca2+-dependent neurotransmltter release by the cells This effect was due to a marked decrease m the concentratlon of extracellular CaZ+ reqmred to provoke the release The concentration of Ca2+ needed to produce half-maximal release shlfted from approx 0 1 mM m the absence of TPA to 0 018 mM m Its presence This actlvlty of TPA was concentration-dependent (half-maximal effect at 4 nM TPA) and was also dependent on the presence of calcmm durmg the premcubatlon period The TPA-induced enhancement of the stimulated release was also observed when Ca2+ entry mto the depolarized cells was partially mhlblted by Co2+ The results suggest that TPA acts synerglstlcally with Ca *+ to activate neuronal component (s) involved m Ca*+-dependent neurosecretlon Phorbol ester Calcium Brain neuron Neurotransmltter

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