Some Factors Which Influence Radiation-Conditioned Behavior of Rats

Abstract

The use of radiation as a stimulus to motivate avoidance behavior in animals has been demonstrated (1-3). For example, rats learn to avoid a compartment in which they have been exposed; however, the avoidance behavior is more pronounced when taste cues are coupled with radiation exposure. The radiation stimulus in these studies does not appear to act through the usual sensory channels. During repeated exposures there is no evidence of excessive urination, defecation, or squealing to indicate that exposure is painful to the animal. Visual effects (phosphenes) have been produced in the dark-adapted eye by ionizing radiations (4). However, conditioned aversions have been produced in opthalmectomized animals, demonstrating that radiation does not act through the retina to motivate the animals (5). Alterations in auditory, touch, taste, and pain sensitivity, as a result of exposure, have been reported (6, 7). These effects, as well as other signs of postirradiation sickness, do not occur until hours or days postirradiation. In contrast, experimentation with the temporal relationships in the conditioning situation indicates that the avoidance responses are due to a prompt effect of the exposure on the animal (3). The present studies are a continuation of efforts to define experimentally the physiological mechanisms which result in the avoidance behavior. Localized radiation exposure, as well as hypophysectomy and adrenalectomy, was employed in an attempt to specify the site of action involved in conditioning through radiation exposure. The effects of these experiences on preference for the fluid was observed in postirradiation consumption tests.