Nicotinic acetylcholine alpha4beta2 receptor regulates the motivational effect of intracranial self stimulation behavior in the runway method.

Recently, it was demonstrated that the priming stimulation effect (PSE) of intracranial self-stimulation (ICSS) with the runway method can be used as a model system to study the motivation that contributes to specific behaviors. It was postulated that these behaviors could be used to compare the effects of various drugs on the mechanism of motivation. In the present study, the influences of nicotine, methyllycaconitine (alpha7 nicotine-receptor antagonist), and dihydro-beta-erythroidine (alpha4beta2 nicotine-receptor antagonist) on motivation were examined using the runway method for ICSS. Electrodes were implanted into the medial forebrain bundle of Wistar rats. The rats ran to the goal lever to get the reward (50 - 200 microA, 0.2 ms, 60 Hz) and pretrial electric stimulation (priming stimulation) in the medial forebrain bundle was performed. The experiment measured the running time from the start box until the rat pressed the goal lever for the reward stimulation. Under these reward and priming stimulation conditions, nicotine (0.2 mg/kg) induced a significant increase in running speed. The nicotine receptor antagonist alpha4beta2 rather than alpha7 showed a dose-dependent antagonistic action on the effect of nicotine on running speed. These results demonstrate that nicotine enhances the running speed towards the goal lever via alpha4beta2 nicotinic receptors and suggest that alpha4beta2 nicotinic receptors influence the brain mechanism of motivation.