Dopaminergic reduction of excitability in nucleus accumbens neurons recorded in vitro

Dopamine (DA) receptor activation has been shown to affect the striatal complex in a multidimensional manner However, the question of whether its net effect on postsynaptic targets in the nucleus accumbens and striatum is excitatory or inhibitory in nature has been a topic of controversy for some time. This study focuses on the effects of DA agonists on indices of postsynaptic cell membrane excitability in nucleus accumbens neurons, such as the amount of intracellular current injection required to elicit spike firing and the membrane potential at which action potentials are evoked. Administration of the nonspecific D-1/D-2 DA agonist apomorphine induced a membrane depolarization that was not mimicked by the D-1 agonist SKF 38393, by the D-2 agonist quinpirole, or by the combined administration of both drugs. On the other hand, subsets of neurons responded to apomorphine or combined D-1/D-2 agonist administration with a response that reversed near -90 mV. Following the administration of apomorphine or the combined administration of the D-1 and D-2 agonists, nucleus accumbens neurons required significantly higher amplitudes of depolarizing current injection to elicit spike firing. These results suggest that coactivation of D-1 and D-2 receptors on accumbens neurons causes a reduction in their membrane excitability.