FURTHER STUDIES OF X-RAY CONDITIONED SACCHARIN AVERSION DURING THE POSTEXPOSURE PERIOD

It has been demonstrated that a postexposure aversion to saccharin-flavored water could be conditioned in rats by a single pairing of the solution with a wholebody X-ray dose (1, 2). The aversion was noted in a preference test initiated 24 hours after termination of exposure. By means of a two-bottle preference test, it has been further shown that 100 r was adequate to condition an aversion to saccharin fluid when the presentation of the saccharin fluid (conditioned stimulus) followed the radiation exposure (unconditioned stimulus) (3). This study indicated that the aversive properties of the X-ray exposure did not terminate with the end of the radiation period. The results of a more recent study indicated that the aversive aspects of a 100-r exposure were present as long as 2 hours after termination of the beam (4). The evidence from these studies clearly indicated that stimuli presented during the early part of the postexposure period were a factor influencing the subsequent preference test. In the studies by McLaurin et al. (5-8) in which the preference test was initiated immediately after X-ray exposure, animals receiving water or no solution as the conditioned stimulus were noted to show a saccharin aversion during the preference test. These investigators questioned whether the saccharin avoidance phenomenon could be attributed entirely to a conditioning process (8). More recently it has been demonstrated that animals receiving no preirradiation solution showed this striking saccharin aversion only when the preference test was begun within a few