Figure 4.
Habituation (tolerance) of the behavioral and physiological effects of nicotinePM. A, Top, Relative changes in NAcc, temporal muscle, and facial skin temperatures (°C). Middle, Changes in NAcc–muscle and skin-muscle temperature differentials (°C). Bottom, Locomotor activity (counts/min) induced by intravenous injections of nicotinePM in drug-naive conditions (left) and after 2 d of previous drug exposure (right). n is the number of averaged tests. Vertical hatched line shows the start of injection. Horizontal lines of respective colors represent values significantly different from preinjection baseline (p < 0.05). B, Mean (±SEM) changes in temperatures (°C) and locomotor activity (counts/min) calculated for 20 min after injection. Data are grouped depending on the drug tested (saline, nicotinePM) and previous drug experience: (Naive), No experience; (nicotinePM), 2 d of nicotinePM exposure. ○Significantly different from saline control (p < 0.05). #Significant differences in the effects of nicotinePM between drug-naive and drug-experienced conditions (p < 0.05). Numbers of trials in each group (n) are shown within bars.