Effects of oxytocin on nicotine withdrawal in rats.

Development of medications that attenuate symptoms of nicotine withdrawal may be useful for facilitating smoking cessation. The neuropeptide oxytocin (OXY) decreases withdrawal signs and other addiction-related effects of several drugs of abuse in animals, but has not been examined in a preclinical model of nicotine addiction. The goal of this study was to examine the effects of OXY on nicotine withdrawal in rats, measured as increases in somatic signs and elevations in intracranial self-stimulation (ICSS) thresholds (anhedonia-like behavior) during antagonist-precipitated withdrawal from a chronic nicotine infusion. Effects of OXY on baseline ICSS thresholds in non-dependent rats were also evaluated. OXY (0.06 - 1.0mg/kg, i.p.) blocked withdrawal-induced elevations in somatic signs in nicotine-dependent rats without affecting somatic signs in non-dependent rats. In contrast, OXY did not affect nicotine withdrawal-induced elevations in ICSS thresholds. Relatively high doses of OXY (0.75 or 2.0mg/kg) elevated baseline ICSS thresholds in non-dependent rats. These findings demonstrate that OXY blocks somatic signs but not elevations in ICSS thresholds during antagonist-precipitated nicotine withdrawal. The ability of higher OXY doses to elevate baseline ICSS thresholds in non-dependent rats may reflect an aversive and/or motoric effect. These data suggest that OXY-based medications may be useful for treating the somatic component of the nicotine withdrawal syndrome, but may not be effective in attenuating withdrawal-induced anhedonia.