Nicotine physical dependence in the mouse: involvement of the alpha7 nicotinic receptor subtype.

Although chronic nicotine produces dependence in mice, the role of specific nicotinic receptors has not been examined in knockout animals. The present study utilized alpha7 nicotinic receptor knockout mice to explore the role of this receptor subunit in nicotine dependence. Mice were chronically exposed to nicotine (0 or 200 microg/ml) in their drinking water and assayed for somatic withdrawal signs, hyperalgesia (tail-flick and hot-plate) and spontaneous activity following nicotine cessation. Nicotine withdrawal produced increased somatic signs in both strains and hyperalgesia in wild-type, but not in knockout animals. These results indicate that the alpha7 nicotinic receptor subunit may mediate some aspects of nicotine dependence.