Fig. 7.

Phosphorylation by protein kinase C inhibits the responses to dopamine, APGWa, and FMRFa. A, Repetitively induced responses to dopamine, APGWa, and FMRFa as indicated, in the absence and presence of TPA. Current amplitudes (I) are normalized to the current response at t = 0 (I₀).Arrows indicate the start of bath perfusion with 50 nm TPA (black diamonds;n = 3–5 for each agonist). Control current responses (contr, open diamonds;n = 5–6 for each agonist) were obtained from experiments performed without change of medium. SEMs are indi cated only by upward error bars. TPA strongly reduces the responses to the agonists. B, Percentage reduction of the FMRFa response after ∼16 min perfusion with 50 nm TPA or with a combination of TPA and the PKC inhibitor staurosporin (1 μm). Staurosporin strongly reduces the inhibitory effect of TPA. *p < 0.005; unpaired ttest; n = 3 for both groups.