Evidence for a cortical locus for the stimulus effect of nicotine.

This study investigated the stimulus properties of nicotine in the rat with the objective of determining the time course of the nicotine-produced interoceptive cue and its relationship to specific brain levels of the drug. The behavioral task employed was shock-escape in a T-maze apparatus. After the injection of nicotine entrance into the nicotine-correct arm of the T-maze resulted in termination of a 0.6 mA shock. When saline was administered, entrance into the opposite arm was rewarded by termination of shock. A high level of discrimination between nicotine and saline was obtained and the degree of discrimination was observed to decrease as the length of time period between nicotine administration and the test of discrimination was increased. This decline in discrimination was closely correlated with the decline in brain levels of nicotine in the cortex suggesting that the stimulus effect of nicotine is directly related to the concentration of nicotine in the cortex.