62 



The effects of nicotine on schedule-controlled behavior have only 

 recently been systematically studied (Morrison and Stephenson 1969; 

 Pradhan 1970; Ando 1975; Davis et al . 1973; Spealman et al. 1981; 

 OeNoble et al . 1982 a,b). In rats, nicotine increases responding main- 

 tained by fixed-interval (FI), variable-interval and differential rein- 

 forcement of low rate schedules of food or water presentation and by 

 schedules of electric shock postponement (Bovet and Bovet-Nitti 1965; 

 Morrison 1967; Pradhan 1970; Ando 1975), In contrast, nicotine decreas- 

 es responding maintained by FR schedules of food or water presentation 

 (Korrison 1967; Pradhan 1970). Qualitatively similar results have been 

 reported in squirrel monkeys maintained by a multiple FI-FR schedule of 

 either presentation of food or termination of a stimulus associated 

 with electric shock (Davis et al. 1973; Spealman et al. 1981). 



Kany drugs from different pharmacological classes can Increase and 

 maintain behavior that leads to self-administration of those drugs 

 (Pickens et al., 1978). It has been shown that iv injections of nico- 

 tine will maintain high rates of lever pressing by squirrel monkeys 

 under a second-order or FI schedule (Goldberg et al. 1981; Spealman and 

 Goldberg 1982). Under the second-order schedule, responding results 1n 

 the presentation of a visual stimulus that is intemittently associated 

 with response-contingent nicotine injections. However, there Is little 

 evidence that rats will self-administer nicotine intravenously unless 

 self-admlristration is induced by a concurrent food delivery schedule 

 (Lang et al. 1977; Smith and Lang, 1980). Even when rats are given pro- 



