Reduced G_i and G_o protein function in the rat nucleus accumbens attenuates sensorimotor gating deficits

Prepulse inhibition of the acoustic startle response (PPI) is a cross-species measure of sensorimotor gating, which is severely disrupted in patients with schizophrenia. PPI deficits can be produced in experimental animals by administration of selective D₂-like dopamine receptor agonists in the nucleus accumbens (NAc). G proteins coupled to these receptors reportedly are altered in the NAc of patients with schizophrenia. Therefore, we sought to determine whether experimental inactivation of intracellular G proteins in the NAc alters PPI. In adult male Sprague-Dawley rats, baseline PPI was determined by presenting acoustic pulse stimuli (120 dB) alone or preceded 100 ms earlier by prepulse stimuli (3, 6 or 12 dB above 70 dB ambient noise). PPI disruption was assessed in the presence of quinpirole (0.0, 0.05, 0.1, 0.5 mg/kg, sc), and pertussis toxin (PTX; 0.05 μg/side) was then infused into the NAc bilaterally. Ten days later, quinpirole-mediated disruption of PPI was significantly reduced; neither PTX alone, nor heat-inactivated PTX had any effect on quinpirole-induced PPI reductions. PPI was significantly higher after PTX infusion upon moderate quinpirole challenge, suggesting that D ₂-like receptors were less effective. PTX treatment significantly reduced basal and dopamine-stimulated [³⁵S]GTPγS binding in the NAc core and shell, and reduced G_iα protein immunoreactivity in the NAc. The results suggest that PPI disruption mediated by D₂-like receptor activation in the NAc depends on coupling to G_i and G_o proteins, alteration of which could cause sensorimotor gating deficits in schizophrenia.