Dopamine modulates the afterhyperpolarization in neostriatal neurones

Intracellular techniques were used to study the actions of dopaminergic D1 agonists on the afterhyperpolarization (AHP) that follows action potentials in rat neostriatal neurones. Dopamine or Cl-APB (10 μM), or 1–10 μM 6-C1-PB all increased AHP amplitude. This effect was blocked by 1 μM SCH-23390, a D1 antagonist, but not by 1 μM sulpiride, a D2 antagonist. Both 500 μM dibutyryl cAMP and 5 μM BayK 8644 induced a similar AHP increase. BayK 8644 occluded the effect of agonists. The results suggest that the action of dopamine is mediated via the recently described protein kinase A enhancement of L-type Ca2+ channels. The results partially explain the decrease in firing frequency induced by dopamine and a possible site of antagonism with cholinergic modulation.