CHRONIC ADMINISTRATION OF ORG-2766 FOR 6 MONTHS PRODUCES A SUBTLE IMPAIRMENT IN STRATEGIC LEARNING BY RATS

Rats were administered saline or 10 mu g of the ACTH(4-9) analog ORG 2 766 on alternate days for 160 days (i.e. 80 injections total). Behavio ral assessments began 1 week later. Locomotor competence was assessed by examining the number of slips and falls made by the animals on a ro tating rod. The rats were also trained on a position task and 10 subse quent position reversals in a 'T' shaped water maze. Exposure to ORG 2 766 failed to affect either locomotor competence or the overall number of errors committed while learning the original position habit and 10 reversals. However, the response accuracy of the ORG 2766-treated ani mals on trial 2 of the reversals was equivalent to that expected by ch ance (58% correct choices), whereas saline-treated animals effectively altered their behavior after experiencing nonreinforcement on the ini tial trial of a reversal (77% correct choices). This result is consist ent with other observations revealing that ORG 2766 can influence atte ntion and, therefore, some cognitive functions.