OPEN-FIELD, LEARNED HELPLESSNESS, CONDITIONED DEFENSIVE BURYING, AND FORCED-SWIM TESTS IN WKY RATS

Wistar Kyoto (WKY) and Wistar rats were observed in four tests; the op en field test (OFT), the conditioned defensive burying (DB) test, and two tests which are considered animal models of depressive behavior, n amely the Porsolt forced-swim test (FST) and the shuttlebox escape res ponding following exposure to inescapable shock, that is, learned help lessness (LH). The four tests were administered according to a semiran domized schedule to control for sequence effects. All rats were later exposed to water-restraint stress and stomachs were subsequently inspe cted for ulcers. Stress ulcer severity was greater in WKY rats. WKY ra ts, as compared to Wistar rats, were hypoactive in the OFT, did not en gage in DB, rapidly acquired the LH task, and were significantly more immobile in the FST. The FST was positively correlated with behaviors in the LH procedure and, to a lesser degree, with DB, but these relati onships were observed only with WKY rats, not Wistar rats. The data su ggested that the use of WKY rats represented a more sensitive procedur e for detecting possible relationships between putative animal models of depressive behaviour.