Iptakalim Preferentially Decreases Nicotine-induced Hyperlocomotion in Phencyclidine-sensitized Rats: A Potential Dual Action against Nicotine Addiction and Psychosis

OBJECTIVE Iptakalim is a putative ATP-sensitive potassium (K(ATP)) channel opener. It is also a novel nicotinic acetylcholine receptor (nAChR) blocker and can antagonize nicotine-induced increase in dopamine release in the nucleus accumbens. Our recent work also shows that iptakalim exhibits a clozapine-like atypical antipsychotic profile, indicating that iptakalim may possess a dual action against nicotine addiction and schizophrenia. METHODS The present study examined the potential therapeutic effects of iptakalim on nicotine use in schizophrenia. We created an animal model of comorbidity of nicotine addiction and schizophrenia by injecting male Sprague-Dawley rats with nicotine (0.40 mg/kg, subcutaneously[sc]) or saline, in combination with phencyclidine (PCP, 3.0 mg/kg, sc) or saline daily for 14 consecutive days. RESULTS During the PCP/nicotine sensitization phase, PCP and nicotine independently increased motor activity over time. PCP also disrupted prepulse inhibition (PPI) of acoustic startle response. Acute nicotine treatment attenuated the PCP-induced hyperlocomotion and PCP-induced disruption of PPI, whereas repeated nicotine treatment potentiated these effects. Importantly, pretreatment with iptakalim (10-20 mg/kg, intraperitoneally) reduced nicotine-induced hyperlocomotion in a dose-dependent fashion. This reduction effect was highly selective: it was more effective in rats previously sensitized to the combination of PCP and nicotine, but less effective in rats sensitized to saline, nicotine alone or PCP alone. CONCLUSION To the extent that the combined nicotine and PCP sensitization mimics comorbid nicotine addiction in schizophrenia, the preferential inhibitory effect of iptakalim on nicotine-induced hyperlocomotion suggests that iptakalim may be a potential useful drug for the treatment nicotine abuse in schizophrenia.