Effects of nicotine on brain area 5-hydroxytryptamine function in male and female rats separated for differences of activity

Abstract

Male and female rats separated according to differences in activity were administered five nicotine (400 μg/kg, s.c.) doses, and 5-hydroxytryptamine (5-HT) function estimated in diencephalon (Dien.) and brainstem (BS) areas of each experimental group. Chemical parameters were studied by comparing 5-HT accumulation in pargyline treated (75 mg/kg, i.p.) rats and it was observed that this factor was significantly lower in nicotine treated high activity (H.A.) rats of both sexes. These effects were most evident in the Dien. of the female, while BS areas were similarly affected in the male rat. 5-HT function appeared to be unaffected by nicotine in L.A. rats, but there was some evidence that this system was stimulated, especially in the Dien. of the female rat (+ 31%). Correlations between the stimulatory effects of nicotine on activity and 5-HT accumulation in the H.A. rat supported previous research which indicated that nicotine can inhibit this chemical system. Pooled data (H.A. + L.A.) reduced the significance of these findings providing further support for using such preselection techniques when attempting to study the pharmacology of a subtle psychoactive drug such as nicotine. Female rats appeared to be, chemically and behaviorally, more sensitive to nicotine which appeared to be somewhat related to the fact that female 5-HT accumulation was faster than that in similarly treated male rats.