Influence of Sex and Female Hormones on Nicotine-Induced Changes in Locomotor Activity in Rats

Abstract

KANÝT, L., I. P. STOLERMAN, C. J. CHANDLER, T. SAIGUSA AND Ş. PÖĞÜN. Influence of sex and female hormones on nicotine-induced changes in locomotor activity in rats. PHARMACOL BIOCHEM BEHAV 62(1) 179–187 1999.—The acute and chronic effects of nicotine (0.4 mg/kg SC) on locomotor activity in photocell cages have been compared in male, female, and ovariectomized hooded rats. In Experiment 1, female rats displayed higher locomotion than males (n = 12); acutely, nicotine-reduced locomotion, and this effect was slightly larger in females than males. Daily administration of nicotine for 21 days produced a similar, gradual increase in activity in both sexes. Tests then confirmed greater activity in females than males and as a function of previous chronic exposure to nicotine (n = 6); there was an activating effect of nicotine challenge but no interaction of nicotine effects with sex. In Experiment 2, ovariectomized rats were primed with 17-β-estradiol (50 μg/kg SC) and progesterone (2.5 mg/kg SC) or vehicle only. Acute administration of nicotine reduced activity in both groups similarly (n = 12). After nicotine daily for 21 days, there was increased activity as a function of both chronic nicotine and hormonal priming, and challenge with nicotine increased activity (n = 6). The effects of these challenges with nicotine were also slightly greater, as a function of previous nicotine exposure and priming. As a whole, these experiments showed robust effects of acute and chronic nicotine administration, sex, and hormonal priming; neither sex nor gonadal hormones had marked influences on changes in locomotor activity produced by nicotine.