Behavioral effects of nicotine withdrawal in adult male and female rats

Nicotine withdrawal may differ between men and women but clinical reports are inconsistent. Two experiments were conducted to examine behavioral effects of nicotine withdrawal in male and female adult rats in dimly-lit and brightly-lit environments. Ninety-six Sprague–Dawley male and female rats received 7 days continuous subcutaneous infusion via ALZET osmotic minipumps filled with saline or 3.16 mg/kg/day nicotine hydrogen tartrate expressed as base. Behavioral observations were made before, during, and after drug administration. During observations, occurrences of empty-mouth-chewing, whole-body-shakes, abnormal grooming, abnormal posture/movement, diarrhea, ptosis, eyeblinks, and any other abnormal behaviors were counted. Cessation of nicotine administration upon pump removal caused a significant increase in withdrawal behaviors in males and females in both environments. In the dimly-lit environment, females showed more withdrawal behavior than males; there was no sex difference in the brightly-lit environment. Males that had received nicotine displayed more withdrawal behavior in the brightly-lit environment than in the dimly-lit environment, while females that had received nicotine displayed similar amounts of withdrawal behavior in both environments. Behavioral symptoms of withdrawal may be more affected by the environment in male rats than in female rats. These experiments are the first to compare nicotine withdrawal in adult male and female rats.