Prenatal cocaine exposure affects the acoustic startle response in adult rats

This study investigated whether prenatal exposure to cocaine alters reflex excitability in adulthood. Pregnant rats received 30 or 60 mg/kg/day cocaine HCl i.g. during gestational days 8-22. Vehicle treated control rats were pair-fed/watered to rats receiving 60 mg/kg cocaine. A non-treated control group was also maintained. At parturition, litters from all four groups were surrogate fostered and then weaned at 21 days of age. In adulthood, rats were tested in an acoustic startle response (ASR) apparatus for 120 trials using a 116 dB signal on 2 consecutive days. On Day 2: subjects received a single injection of d-amphetamine sulfate s.c. (1.0 mg/kg) just prior to testing. ASR amplitude and latency were recorded. For average amplitude, significant effects for prenatal treatment were observed. Cocaine-exposed female rats demonstrated decreased ASR amplitude compared to offspring of pair-fed controls during both the initial test Session and following amphetamine administration as well. Overall, amphetamine increased startle. For latency, there were no significant treatment effects or effects of amphetamine administration. However, preplanned comparisons indicated that prenatal cocaine exposure interacted with trial block. Therefore, these data indicate that prenatal cocaine decreased startle amplitude in adults, primarily in females, and that startle-elicited amphetamine responses were dampened as well. The effects on latency indicate that amphetamine does not alter reaction times in prenatal cocaine exposed rats while it does in controls.