Inhibitory effect of cyclooxygenase inhibitors on the step-through passive avoidance performance in mice treated with NC-1900, an arginine-vasopressin fragment analog

Abstract

To examine the participation of endogenous cyclooxygenase (COX) in the mnemonic effect of NC-1900, an arginine-vasopressin fragment analog, the latencies of mice in the step-through passive avoidance (PA) task were determined following the administration of COX inhibitors and/or NC-1900 (1 ng/kg). When administered immediately after the acquisition trial (Acq) in the PA task, indomethacin (20 mg/kg), a nonspecific COX inhibitor, and NS-398 (10 and 20 mg/kg), a specific COX-2 inhibitor, but not piroxicam (10 and 20 mg/kg), a specific COX-1 inhibitor, decreased the latency on the retention trial (Ret). The mnemonic effect of 1 ng/kg NC-1900 on the Ret in the PA task was also inhibited by the administration of either indomethacin (20 mg/kg) or NS-398 (20 mg/kg) but not by piroxicam. However, when 20 mg/kg indomethacin and NS-398 were administered 3 h after the Acq, the increase in Ret latency induced by NC-1900 was not inhibited. These results suggested that the action of NC-1900 on the early stage of memory formation in the PA task may be modulated by endogenous COX-2 but not by COX-1.