Rat strain differences in the ability to disrupt sensorimotor gating are limited to the dopaminergic system, specific to prepulse inhibition, and unrelated to changes in startle amplitude or nucleus accumbens dopamine receptor sensitivity

Previous studies indicate that a variety of pharmacological agents interfer e with the prepulse inhibition of the acoustic startle (PPI) response inclu ding phencyclidine (PCP), 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT ), amphetamine, and apomorphine. Strain differences have been observed in t he ability of apomorphine to disrupt PPI, although the degree to which thes e strain differences occur after administration of nondopaminergic drugs or the degree to which differences can be observed in other models of dopamin e (DA) receptor activation has not been elucidated. The present study teste d the effects of apomorphine, amphetamine, 8-OH-DPAT, and PCP on PPI in the Sprague Dawley and Wistar rat strains. Because apomorphine disrupts PPI vi a activation of DA receptors in the nucleus accumbens, apomorphine-induced hyperlocomotion, also a behavioral model of nucleus accumbens DA receptor a ctivation, was measured in both rat strains. Administration of PCP or 8-OH- DPAT attenuated PPI in both strains, whereas apomorphine and amphetamine on ly attenuated PPI in Wistar rats. The ability of apomorphine to increase mo tor activity in the absence of a startle-eliciting stimulus was similar in the two strains, as was apomorphine-induced hyperlocomotion, A time course analysis of the effects of apomorphine on startle response in Sprague Dawle y rats found that changes in the magnitude of PPI followed changes in basic startle amplitude, Similarly, no apomorphine-induced attenuation of PPI wa s observed in Sprague Dawley rats after 8-OHDA-induced DA receptor supersen sitivity in the nucleus accumbens. These data suggest a dissociation betwee n the effects of DA receptor agonists in PPI and other behavioral models of DA receptor activation.