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of rats (the after group) received saline before and .8 mgAg of (-)-nicotine 

 after the session. Injections occurred 10 minutes before and after the 

 session. On day 31 of chronic nicotine dosing the after group received the .8 

 mg/kg dose of (-)-nicotine before the session as a test for tolerance; saline 

 was administered after the session. The before group received its usual pre- 

 session (-)-nicotine and post-session saline injections on day 31. Fonowing 

 day 31 the before and after groups continued to receive their usual pre- and ■ 

 post-session {-)-nicotine or saline injections except that testing occurred • 

 only on Monday through Friday. 'On"Tve§ren^~tfie rats from both groups^received 

 a single injection of .8 mg/kg of {-)-nicotine. Beginning on day 52 of chronic 

 {-)-nicotine dosing the acute (-)-nicotine dose-effect function-s were redeter- 

 mined. One day per week (Thursdays or Fridays) a test dose of (-)-nicotine was 

 substituted for the usual presession injection, .8 mg/kg (-)-nicotine or 

 saline, in both the before and after groups; saline was administered post- 

 session to both groups. The substitute doses of (-)-nicotine were .2, .4, .8, 

 1.2 and l.d mg/kg adrainistered in an ascending order. Additionally, both 

 groups of rats received saline presession as the substitute dose and .8 mg/kg 

 of (-)-nicotine post-session the week before (day 45) and the week after the 

 acute (-)-nicotine dose-effect function was redetermined. Chronic (-)-nicotine 

 dosing was terminated after approximately 100 consecutive days. Si rats 

 received their last dose of chronic (-)-nicotine on a Exiday. Following ter- 

 mination of chronic (-)-nicotine dosing the persistence of tolerance was 

 examined over the next four weeks. Animals were tested Monday through Friday 

 with Wednesdays serving as baseline sessions, Thursdays serving as saline 

 control sessions, and Fridays serving as (-)-nicotine test sessions. On 

 Fridays .8 mg/kg of (-)-nicotine was administered presession to all rats. 



