Avoidance of and anticipatory responses to shock in prenatally X-irradiated rats

Abstract Male MP1 albino rats were exposed to X-irradiation in utero at a single dose of 200 R on Day 17 of gestation. This experiment was aimed to determine just how irradiated rats could differ from controls in a shuttlebox avoidance response. Irradiated rats had a significantly higher anticipatory response to CS which predicts shock, and also made a significantly higher incidence of consecutive anticipatory responses during the CS-US interval. Thus, facilitated avoidance behavior in irradiated rats is probably a consequence of a strong tendency to running induced by shock in shuttlebox. Since cell destruction caused by irradiation was evident in the primordial hippocampus, a smaller hippocampus developed. The dendrites of pyramidal neurons in Ammon's horn were abnormally oriented. Behavioral changes in shuttlebox after irradiation may be related to the hippocampus abnormality, based on stress-arousal interpretation of hippocampal functioning in a situation employing noxious stimulation.