IV nicotine self-administration in rats using the consummatory operant licking response

Nicotine self-administered by tobacco smoking or chewing is very addictive in humans. Rat models have been developed in which nicotine is self-administered IV by the rats pressing a lever. However the reinforcing value of nicotine is much less in these models than the addictiveness of human tobacco use would indicate. The IV nicotine self-administration operant lever press model does not fully capture important aspects of tobacco use in humans. Conditioned oral consumption actions of smoking or chewing tobacco may play important roles in tobacco addiction. Neural circuitry underlying essential food consummatory responses may facilitate consummatory aspects of tobacco intake. To capture this motor consummatory aspect of tobacco addiction in the rat model of nicotine self-administration, we have developed a method of using a licking response instead of a lever press to self-administer IV nicotine. Sprague-Dawley rats were trained to lick one of two waterspouts for IV nicotine (0.03 mg/kg/infusion). With the licking response rats self-administered stable nicotine levels throughout 24 sessions (45 min each) of testing. The number of total licks/session significantly increased in a linear fashion over that period. The number of licks/infusion was substantial, rising steadily with training to an average of over 100 licks/infusion. Including the consummatory motor act with nicotine self-administration could help better model the compulsive aspects of tobacco addiction in humans.