Dopamine inhibits burst-firing of neurosecretory cell R 15 in Aplysia californica: establishment of a dose-response relationship.

Burst-firing in neurosecretory cell R 15 of Aplysia californica is inhibited by the bath application of dopamine. Voltage-clamp analysis reveals a complex series of changes in the current-voltage relationship of R 15. Dopamine reduces the inward current in the region of negative slope conductance and tends to linearize the current-voltage curve. A variable increase in potassium conductance is frequently observed. The loss of inward current in the region of negative slope conductance is dose-dependent, highly reproducible and relatively resistant to desensitization, and for these reasons a valid dose-response relationship can be described. The dose-response curve is sigmoidal in shape and rises from a minimal effect near 50 microM to a maximal effect near 500 microM. This dose-response curve is useful as a standard of comparison in studies of agonists and antagonists. A protocol for the quantitative study of this system is described, and the constellation of changes in the current-voltage curve produced by dopamine is discussed.