NICOTINE WITHDRAWAL - A BEHAVIORAL-ASSESSMENT USING SCHEDULE-CONTROLLED RESPONDING, LOCOMOTOR-ACTIVITY, AND SENSORIMOTOR REACTIVITY

Three different behavioral measures were used to assess the effects of abrupt cessation of chronic nicotine treatment. Nicotine (0, 3, or 6 mg/kg per day) was continuously administered for 12 days in rats by su rgically implanting Alzet osmotic mini-pumps subcutaneously. Experimen t 1 employed a light/dark discrimination task. There were no significa nt effects on number of responses or percent correct responding either during nicotine administration, or following cessation of nicotine. E xperiment 2 examined ambulatory (locomotor) and nonambulatory activity . Chronic nicotine administration produced significant dose-dependent increases in both ambulatory and nonambulatory activity during the fir st 3 days of exposure. However, no significant alterations were seen i n activity levels following nicotine cessation. Experiment 3 examined sensorimotor reactivity using the auditory startle response. During ni cotine withdrawal, significant increases were seen in startle amplitud e in both nicotine groups for 4 days. Nicotine (0.4 mg/kg, IP) adminis tered before startle testing during the withdrawal phase attenuated th e increased reactivity seen during nicotine cessation. These studies i ndicate that 1) rats display increased sensorimotor reactivity after c essation of chronic nicotine exposure, and 2) the expression of nicoti ne dependence and withdrawal is dependent on the behavioral task emplo yed.