69 



INSERT FIG. 3 



Figure 3 shows the effect of prog-anned infjsions delivered irde- 

 pendently o*' responding cr nicotine-trairtained lever pressing. The per- 

 cent decrease in the number of resrcnse-contingent infi-sions was 

 inversely related to the orograrrmed interinfusior interval (solid 

 line). The sum c* respo''se contingent in-usiors plus response 'ndepen-, 

 dent progranned infusions was stable across sessions ^cas'red r'ne). 



Effect of Varying FP Size on Nicotin e Va^n-ained Leve" Press ire . 



The effect of ''ncreasipo f'e "P size or the nurrbe'* of lever presses and 



i^f-jsions (32 ;-g. kg) is s^"own in F-g. 4. Increases in ratio size up to 



INSEPT FIG. <*• 



5 resulted in substantial increases in the rur.ber of "ever presses 

 (Fig. 4). At ratios of 6 and 7 the noirbe- of lever presses rsinained 

 stable and a further increase in ratio size to 8 •■esijlted in a decrease 

 in the rur.ber of lever presses. The nuirber of infusions also remained 

 stable across several ratios (1 to 6), then aecreased at ratios of 7 



and 8 (dashed lire Fig. 4). 



... J •■■•■; 



Effects of f^ec amy latrine, h'exemethonium or Naloxone on Nicotine 

 f<aintained Responding . Before each irecan-^-lapine adniristratirr respond- 

 ing by four rats was examined in sessions in which a subcutaneous 

 saline injection was giver (Fig. 5, open bar). When Tiecamylamine (C.75 



INSERT FIG. 5 



11 



