MECAMYLAMINE BLOCKADE OF NICOTINE RESPONSES - EVIDENCE FOR 2 BRAIN NICOTINIC RECEPTORS

Mice of two inbred strains, DBA and C3H, were pretreated with mecamylamine before challenge with nicotine. Mecamylamine blocked nicotine-induced seizures, enhanced startle, and alterations in respiratory rate, Y-maze activity, heart rate and body temperature. Mecamylamine blocked nicotine-induced seizures and enhanced startle with IC50 values of less than 0.1 mg/kg. The other nicotine effects were blocked by mecamylamine with IC50 values between 0.8 and 2.8 mg/kg. Strain differences in sensitivity to mecamylamine blockade were also detected. These results suggest that nicotine elicits its effects at two receptors, which may be those labeled with [125I]-.alpha.-bungarotoxin and with [3H]-nicotine.