Effects of synaptic blockade on DA neuron spontaneous activity. Synaptic isolation by blockade of intraretinal synaptic inputs to DA neurons with a blocker mixture [containing the following (in μm): 20 CNQX, 50 AP-5, 30 bicuculline, 100 imidazole-4-acetic acid sodium salt, 3 strychnine, 30 eticlopride] increases bursting. A typical recording of DA neuron spontaneous activity in the absence (top) and presence (bottom) of the blocker mixture is shown.