Fig. 7.

Effects of conditioning on locomotor responses to nicotine in a cross maze. One group of rats were pretreated with daily injections (s.c.) of saline or nicotine (0.4 mg/kg) for 16 days (chronic treatment) and returned to their home cages after each injection (non pre-exposed rats). On test days, the rats (N = 6 per group) were pretreated with MPEP (5.0 mg/kg, i.p. filled columns) or its saline vehicle (open columns), using a counter-balanced experimental design, 30 min before they were given a second s.c. injection (test treatment) of saline or nicotine. The same experimental design on the test days was used for a second group of rats which were pre-exposed to the maze by testing them for 15 min per day after each of their chronic injections. The data are expressed as means ± SEM. Significantly different from habituated to the maze with saline **P < 0.01. Significantly different from rats given i.p. saline on the test day ++P < 0.01