106 



stability was defined as the absence of any consistent increasing trends In 

 response rates over 10 consecutive sessions. Once responding stabilized, 

 sterile 0.91 physiological saline injections were given once or twice per week 

 for several weeks to adapt the animals to the injection procedure. Dose-effect 

 functions for {-)-nicotine (nicotine hydrogen tartrate. Chemicals Procurement 

 Laboratories Inc.) were then determined. (-)-Nicotine (0.5, .1, .2, .4, .8 

 mg/kg as the base in saline particle) administered only once per week If the 

 following criteria were met. A given day served as a baseline control, flay 

 (day 1) if the response rate -toe— wat^day was within the rati^ of rates 

 obtained over the immediately preceeding 5-10 days of stable responding. 

 Saline was administered on the next day (day 2). If responding after saline 

 remained within the range of previous stable responding, (-)-nicotine was 

 administered on the following day (day 3). This sequence occurred once per 

 week with the remaining two days serving as baseline sessions. Injections were 

 administered s.c. in a volume of 1 ml/kg of body weight. (-)-Nlcotlne doses 

 v/ere administered in an ascending order. A complete dose-effect function was 

 determined for each rat and then repeated. (-)-Nlcotlne effects were expressed 

 as a percentage of the mean of the preceeding baseline and saline data. These 

 percentages were averaged to give mean saline and (-)-nlcotine effects for each 

 rat, which were then averaged across animals to yield group functions.- 



Four weeks after the completion of the acute (-)-nlcotine ^ose-effect 

 determinations the chronic dosing phase was begun. The rats were divided Into 

 two groups (N=7 per group) and watched for overall session response rat. 

 Saline was Injected twice per day for five consecutive sessions, with the mean 

 of these five sessions serving as control data for the chronic dosing phase. 

 For the next 30 consecutive days, one group of rats (the before group) received 

 .8 mg/kg of (-)-nicotine before and saline after the session. The other group 



