D1 Receptor Activation Enhances Evoked Discharge in Neostriatal Medium Spiny Neurons by Modulating an L-Type Ca2+ Conductance

摘要: Most in vitro studies of D1 dopaminergic modulation excitability neostriatal medium spiny neurons have revealed inhibitory effects. Yet made more intact preparations shown that receptors can enhance or inhibit the responses to excitatory stimuli. One explanation for these differences is effects on are dependent changes membrane potential occurring response cortical inputs seen only preparations. To test this hypothesis, we obtained voltage recordings from slices and examined impact receptor stimulation at depolarized hyperpolarized potentials. As previously reported, evoked discharge was inhibited by agonists when holding negative potentials (approximately −80 mV). However, −55 mV), enhanced activity. At potentials, cAMP analogs prolonged induced slow subthreshold depolarizations increased duration barium- TEA-induced Ca2+-dependent action Both were blocked L-type Ca2+ channel antagonists (nicardipine, calciseptine) occluded agonist BayK 8644—arguing receptor-mediated activity mediated enhancement currents. These results reconcile previous vivo showing dopamine activation either activity, depending level depolarization.