Enhancement of sensitization to nicotine-induced ambulatory stimulation by psychological stress in rats.

1. The authors investigated the influence of psychological stress (PSY-stress) on sensitization to nicotine (0.5 mg/kg, s.c.)-induced ambulatory stimulation. 2. Rats were exposed to the emotional responses of animals which received foot-shock (FS), which they, themselves, did not receive. Ten daily exposures to PSY-stress for 20 min enhanced sensitization to the nicotine-induced ambulatory stimulation compared to that in non-stress rats. 3. However, the increased serum corticosterone levels following nicotine (0.5 mg/kg, s.c.) administered 24 hr after the tenth injection of nicotine in the behavioral study was almost the same in the rats exposed to PSY-stress as compared to non-stress rats. 4. These results suggest that PSY-stress may promote sensitization to nicotine-induced ambulatory stimulation and that the combined effect of PSY-stress and nicotine would facilitate the development of sensitization to nicotine.