Rat strain differences in startle gating-disruptive effects of apomorphine occur with both acoustic and visual prepulses

Prepulse inhibition of startle (PPI) is an operational measure of sensorimotor gating that is impaired in schizophrenia and is disrupted in rats by dopamine (DA) agonists like apomorphine (APO). Using acoustic prepulses and acoustic startle pulses, previous studies have demonstrated heritable strain differences between Sprague Dawley (SD) and Long Evans (LE) rats in the sensitivity to the PPI-disruptive effects of APO. As PPI deficits in schizophrenia are evident with both uni- and cross-modal stimuli, we tested whether strain differences in the gating-disruptive effects of APO occur with a cross-modal visual and acoustic stimulus combination. APO caused a dose-dependent disruption of both acoustic and visual PPI in SD rats. Compared to LE rats, SD rats were more sensitive to the PPI-disruptive effects of APO with both acoustic and visual PPI. These findings suggest that SD vs. LE strain differences in PPI APO sensitivity are mediated outside of the auditory system, within higher circuitry that regulates or processes multi-modal information. The present findings provide further validation for this heritable model of impaired sensorimotor gating in schizophrenia, which can be detected across multiple sensory modalities.