Nicotine administration interacts with housing conditions to alter social and non-social behaviors in male and female Long-Evans rats

Despite the fact that the anxiety-relieving effects of smoking are widely reported by smokers, human laboratory studies have not found consistent evidence for this effect. In animals, contrasting results also have been reported, with Sprague-Dawley rats unaffected by nicotine in behavioral tests of anxiety but with other rat strains (e.g., Wistar, Fischer-344) displaying behaviors indicative of anxiolysis. The present experiment used the social interaction test to evaluate effects of nicotine (12 mg/kg/day) chronically administered via minipump on social and non-social behaviors in 48 male and 48 female Long-Evans rats-a strain that has not previously been evaluated and that is known to differ from Sprague-Dawleys in other behavioral responses to nicotine. Because environmental conditions can alter behavioral effects of drugs, animals lived in either individual or same-sex group housing. Social interactions were measured on day 10 of drug administration and social behaviors (touch, follow, sniff-other, wrestle) as well as non-social behaviors (anxiety-related behaviors: freezing, grooming-self; exploratory behavior: moving) were scored. Group housing decreased social behaviors and increased anxiety-related behaviors. Nicotine's effects depended upon housing condition, such that nicotine further decreased social behaviors and increased anxiety-related behaviors of group-housed animals, with weaker effects in single-housed animals. Overall, the results suggest that nicotine's effects are modified by environmental conditions, and that nicotine administration at this dosage and in this particular rat strain results in anxiogenic effects.