INTRACEREBROVENTRICULAR NICOTINE AND MECAMYLAMINE ALTER RADIAL-ARM MAZE PERFORMANCE IN RATS

In rats, the effects of an intracerebroventricular (ICV) nicotinic ago nist nicotine (NIC), the nicotinic antagonist mecamylamine (MEC), and combinations of NIC + MEC were assessed in a radial-arm maze (RAM). In experiment 1, exploratory behavior was assessed in untrained rats (N = 13). The rats received 4 mu g, 8.65 nmol NIC (NIC 4), 200 mu g, 0.98 mu mol MEC (MEC), and saline (SAL) ICV infusions. NIC 4 caused a sign ificant increase in choice distribution compared to SAL (P < 0.025). I n experiment 2, rats (N = 10) were trained to perform a working memory task for food reinforcement in the RAM. ICV doses of SAL, NIC 4, NIC 8, MEC, MECNIC 4, and MECNIC 8 were administered after completion of t he training period. MEC caused a significant deficit in choice accurac y when compared to SAL (P < 0.025). This deficit was reversed when NIC 8 was coadministered with MEC (P < 0.05). There were no significant e ffects on choice latency for either study. The effects of ICV NIC and MEC on RAM performance are generally similar to their systemic effects in that NIC improves and MEC impairs choice accuracy. The reversal of the MEC-induced choice deficit by ICV NIC administration has not been reported with systemic administration. ICV MEC induces a choice accur acy deficit without increasing choice latency. This has not been seen with systemic MEC administration. The current result implies that the MEC-induced choice accuracy deficit did not result from MEC-induced se dation. The data indicate that previously reported changes in choice a ccuracy from peripherally administered NIC and MEC result from their c entral effects, (C) 1993 Wiley-Liss, Inc.