REVERSAL OF LEARNED HELPLESSNESS BY CHRONIC LITHIUM TREATMENT AT A PROPHYLACTIC LEVEL

1. The effect of chronic lithium (Li) administration in a learned help lessness (LH) model was investigated. Female Wistar rats (190-210 g) r eceived either tap water ad libitum (N = 56) or 20 mM LiCl (N = 63) in the drinking water or were water restricted (35% based on tower liqui d intake of rats receiving lithium, N = 40) for 30 days. On the 28th d ay, each of these groups was divided into three subgroups which receiv ed escapable (ES), inescapable (IS) or no shock (NS) treatment in shut tle boxes. All groups were submitted to the escape test on the 29th da y and sacrificed on the 30th day, when blood samples were taken for me asurement of serum lithium, sodium and potassium concentrations. 2. Th e NS group had lower serum Li levels (0.36 +/- 0.06, N = 15) than the ES (0.46 +/- 0.07, N = 15) or IS group (0.44 +/- 0.09, N = 25). The Li -pretreated group subjected to IS had a more effective escape performa nce than the IS group under water restriction and showed the same beha vior as animals not submitted to shocks. 3. We conclude that chronic t reatment with Li at a serum level of 0.44 +/- 0.09 mEq/l prevents lear ned helplessness in rats. These results corroborate the validity of th e use of this model for the assessment of the capacity of Li to protec t against some depressive episodes.