DISSOCIATION BETWEEN STARTLE AND PREPULSE INHIBITION IN RATS EXPOSED TO GAMMA-RADIATION AT DAY 15 OF EMBRYOGENY

The role of prenatal trauma in disordered sensory gating was explored in albino rats of the Sprague-Dawley strain. Pregnant rats were expose d to 1.5 Gy (0.15 Gy/min) of the whole-body gamma radiation on days 15 , 17, or 19 of gestation. Controls were sham-exposed during 10 min in the same conditions. Exposed and control offsprings were evaluated for the auditory startle response (ASR) and its gating by either the habi tuation process or by the preceding weak sensory stimulus in the prepu lse inhibition of startle (PPI) procedure. The tests were conducted wh en the animals reached 27 and 57 days of age. A noticeable hyperrespon ding and delayed habituation of startle were found in rats exposed at E15, with meager effects in rats exposed at E17 and E19. Maximal defic it was obtained on tests conducted on P57 but not on P27. However, in rats pretreated with amphetamine, dysfunctional startle was unmasked a lready on the P27 test. By contrast, PPI was insensitive to the damagi ng effect of prenatal irradiation at either period. This dissociation is reminiscent of one observed in patients with posttraumatic stress d isorder (PTSD). (C) 1998 Elsevier Science Inc.