The α3ß4* nicotinic acetylcholine receptor subtype mediates nicotine reward and physical nicotine withdrawal signs independently of the α5 subunit in the mouse.

ABSTRACT

The 15q25 gene cluster contains genes that code for the α5, α3, and ß4 nicotinic acetylcholine receptor (nAChRs) subunits, and in human genetic studies, has shown the most robust association with smoking behavior and nicotine dependence to date. The limited available animal studies implicate a role for the α5 and ß4 nAChR subunits in nicotine dependence and withdrawal; however studies focusing on the behavioral role of the α3ß4* nAChR receptor subtype in nicotine dependence are lacking. Because of the apparent role of the α3ß4* nAChR subtype in nicotine dependence, the goal of the current study was to better evaluate the involvement of this subtype in nicotine mediated behavioral responses. Using the selective α3ß4* nAChR antagonist, α-conotoxin AuIB, we assessed the role of α3ß4* nAChRs in acute nicotine, nicotine reward, and physical and affective nicotine withdrawal. Because α5 has also been implicated in nicotine dependence behaviors in mice and can form functional receptors with α3ß4*, we also evaluated the role of the α3ß4α5* nAChR subtype in nicotine reward and somatic nicotine withdrawal signs by blocking the α3ß4* nAChR subtype in α5 nAChR knockout mice with AuIB. AuIB had no significant effect on acute nicotine behaviors, but dose-dependently attenuated nicotine reward and physical withdrawal signs, with no significant effect in affective withdrawal measures. Interestingly, AuIB also attenuated nicotine reward and somatic signs in α5 nAChR knockout mice. This study shows that α3ß4* nAChRs mediate nicotine reward and physical nicotine withdrawal, but not acute nicotine behaviors or affective nicotine withdrawal signs in mice. The α5 subunit is not required in the receptor assembly to mediate these effects. Our findings suggest an important role for the α3ß4* nAChR subtype in nicotine reward and physical aspects of the nicotine withdrawal syndrome.