Nicotine and varenicline ameliorate changes in reward-based choice strategy and altered decision-making in...

Patients suffering from neuropsychiatric disorders such as substance use and addiction disorders show impaired decision-making, which may be associated with their psychiatric disorders. Previously, using a gambling test for rodents, we demonstrated that methamphetamine-dependent rats showed alterations in their decision-making strategy. In this study, we investigated the effect of nicotine on impaired decision-making strategy in rats which have been treated repeatedly with methamphetamine. Nicotine has previously been shown to have therapeutic effects on attentional and cognitive abnormalities in psychosis. Rats were administered methamphetamine subcutaneously (sc) at 4 mg/kg once a day, for 30 days, and their decision-making was then assessed with a rodent gambling task. We found that methamphetamine-treated rats preferred the high-risk/high-return actions, which is consistent with our previous findings. Methamphetamine-induced impairment of decision-making was reversed by daily nicotine treatment (0.3 mg/kg, sc). This effect was associated with the reduction of lose-shift behavior after negative reward prediction error. Repeated treatment with nicotine had no effects on arm-choice behavior in naïve rats. Varenicline, an α4β2-nicotinic acetylcholine receptor partial agonist, also ameliorated the altered decision-making in methamphetamine-treated rats. Our findings suggest that nicotine treatment is useful for ameliorating the altered decision-making caused by methamphetamine treatment, and that the α4β2-nicotinic acetylcholine receptor is a therapeutic target for poor decision-making.