121 



dosing. Redetermination of the nicotine dose-effect function (.2 - 1.6 a»gAg) 

 while daily dosing continued showed that the before" and after groups were 

 affected similarly at all doses. Following cessation of chronic dosing, both 

 groups lost tolerance at similar rates. Since factors such as age, gender and 

 strain have been shown to influence the behavioral effects of nicotine in both 

 rats and mica (3ryson et al_. , 1981; Hatchel and Collins, 1977; Morrison, 1968), 

 and since the mouse has only recently been used in behavioral pharmacological 



studies involving schedules of inforcement, critical comparisons between this 



\^ 



study and this present onecannot be- made at the present time. "^ . 



Nicotine administered acutely decreased food-maintained FR 32 response 



rates in a dose-dependent fashion. The reduction in total session responding 



was due to a complete suppression of responding early in the session followed 



by a rapid recovery of control-like rates. Similar effects of nicotine on FR 



schedules have been reported previously in rats {Pradham, 1970; Domino and 



Lutz, 1973; Dougherty et al_. , 1981), mice (Hendry and Rosecrans, 1982) and 



squirrel monkeys (Davis etal^., 1973; Spealman et al_. , 1981). In contrast, 



Harrison (1967) reported that at doses similar to those used in the present 



study (.05 - .4 mg/kg), total session response rates were increased in rats 



responding under an FR 30 water reinforcement schedule. In Morrison's study, 



however, the daily session was 90 minutes in duration; the session (Ktern of 



responding consisted of.an initial reduction in respon di ng fo l 1 owed %j^' 1 arge 



rate increases after 60 minutes had elapsed. In the present study, small 



Increases in rates were observed in some subjects following recovery of 



responding after nicotine administration. More consistent rate^ inert*.** v nay 



not have been observed here because test sessions were 30 minutes In duration. 



Pradham (1970) also has reported that nicotine increased FR rates during 60 



minutes test sessions. /FR and continuous avoidance components alternated with- 



