Effects of mecamylamine on flash-evoked potentials, body temperature, and behavior in Long-Evans rats

This experiment examined the effects of mecamylamine, a nicotinic acetylcholine receptor antagonist, on flash-evoked potentials (FEPs) recorded from the visual cortex (VC) and superior colliculus (SC) of chronically implanted male Long-Evans rats, and on body temperature and open field behavior. FEPs were recorded at 20 and 35 min following intraperitoneal injections of saline, and of 0.3, 3.0, and 10.0 mg/kg mecamylamine on separate days. The 0.3 mg/kg dose did not produce significant effects. The amplitude of VC components N(30), P(48), and P(87) increased. N(150) and P(231) decreased, and P(23), N(40), N(58), and N(68) were unchanged following administration of the 10.0 mg/kg dose. In the SC, component P(28) was unaffected, 1339 was reduced, and N(49) was augmented by the 10.0 mg/kg dose. All component peak latencies were increased by the 3.0 and 10.0 mg/kg doses. Significant hypothermia was also produced by the 3.0 and 10.0 mg/kg doses, suggesting that this was the basis for the increased latencies. The 10.0 mg/kg dose produced a significant decrease in movement during the recording sessions. In subsequent open field observations, both line crossings and rearings were reduced by the 3.0 and 10.0 mg/kg doses. The results suggest that endogenous acetylcholine acting on nicotinic acetylcholine receptors plays at most a modest role in producing FEPs recorded from the VC and SC. (C) 2010 Elsevier Inc. All rights reserved.