104 



A dose of 1.2 mg/kg of nicotine which reduced response rates to 151 of control 

 levels was then administered daily until tolerance developed in the before 

 group. Responding in the after group was not affected by postsession injec- 

 tions of nicotine. When the nicotine dose-effect functions were redeterained 

 while chronic dosing continued, the two groups of mice were found to be equally 

 tolerant to the rate-decreasing effects of nicotine. These findinos -jfire 

 Interpreted as indicating that behavioral variables do not influence the 

 development of tolerance to nicotine. 



^,- «.a , ^ 



The present study used the before/after dosing paradigm to investigate 

 whether behavioral factors may be involved in the development of tolerance to 

 nicotine. In rats responding under an FR 32 food schedule, tolerance to the 

 disruptive effects of nicotine developed with chronic dosing. Behavioral 

 factors were found to be involved in the development of tolerance to nicotine, 

 since the before group showed a significantly greater degree of tolerance than 

 the after group when comparisons were made at several times during chronic 

 dosing and once chronic dosing was terminated. 



METHODS 

 Animals 



Fourteen naive male Long-Evans hooded rats (Blue Spruce Farms, ^taoont, 

 N.Y.), 90-120 days old and weighing 325-350 g at the start of the experiment 

 were used. The rats were maintained at approximately 851 of their ad libitum 



weights which was determined from the last five days of a two week free-feeding 

 period; weights were maintained by restricted feedings with Purina Rodent Chow 

 approximately 30 minutes after daily testing. Animals were singly housed in 

 wire mesh cages in which water was always available. Temperature and humidity 



