Different effects of chronic nicotine treatment regimens on body weight and tolerance in the rat.

The effect of different chronic nicotine administration regimens on body weight and the development of tolerance was examined in female rats. Groups of animals were either treated with nicotine via a subcutaneous continuous release pellet or via two injections each day of either a high (5.6 mg/kg) or low (0.8 mg/kg) dose. Both the Pellet and Low injection groups showed a progressive weight loss during nicotine treatment followed by a weight gain upon cessation of treatment, but the time course and size of these weight changes were quite distinct. In contrast, the High injection group gained weight during the 17 days of nicotine treatment. Tolerance, as measured by locomotor activity following an acute injection of nicotine 1 week after cessation of chronic nicotine treatment, was evident only in the Low injection group. This study demonstrates that the regimen in which nicotine is administered is an important factor in determining the behavioral effects produced by chronic nicotine treatment.