Taste aversions conditioned with multiple exposures to gamma radiation: abolition by area postrema lesions in rats.

Lesions which destroy the area postrema (AP) and damage the adjacent nucleus of the solitary tract (NTS) attenuate conditioned taste aversions (CTA) induced by a variety of pharmacological agents as well as exposure to radiation. In this experiment the possibility that AP lesions might not attenuate a radiation-induced CTA, when multiple pairings of the novel taste stimulus and exposure to gamma radiation occurred, was examined. Three groups of male rats received lesions of AP and another 3 groups received sham lesion. Following a recovery period all rats were adapted to a 23.5 h/day water deprivation schedule. A sodium saccharin solution (0.1%) was offered to all rats during the regular drinking period (0.5 h) on two days per week, with water available on the other days. Access to saccharin was followed by exposure to 0, 20 or 40 rad of gamma radiation with one lesioned and one sham-lesioned group assigned to each dose level. After 4 pairings of saccharin with radiation the sham-lesioned groups exposed to 20 and 40 rad of radiation exhibited a dose-dependent aversion to the saccharin solution (P less than 0.0001), whereas the AP-lesioned groups did not differ significantly from the 0 rad sham-lesioned group. Subsequent two-bottle choice tests, which are a more sensitive measure of CTA, confirmed that the AP-lesioned rats exposed to 20 and 40 rad radiation did not develop a significant CTA relative to the two 0 rad radiation groups. Thus, AP lesions abolished the CTA normally induced by multiple pairings of saccharin with exposure to 20 or 40 rad gamma radiation.