Nicotine, but not mecamylamine, enhances antidepressant-like effects of citalopram and reboxetine in the mouse forced swim and tail suspension tests

Current literature suggests that nicotinic acetylcholine receptors (nAChRs) are involved in major depression. In rodents, antidepressant-like effects of both nicotine and the non-selective nAChR antagonist mecamylamine have been reported. Nicotine increases serotonergic and noradrenergic neuronal activity and facilitates serotonin and noradrenaline release. Thus, we hypothesise that nicotine may enhance the behavioural effects of serotonin (e.g., citalopram) and/or noradrenaline (e.g., reboxetine) reuptake inhibitors. Here, we tested if nicotine enhanced the activity of citalopram or reboxetine in the mouse forced swim test (mFST) and the mouse tail suspension test (mTST). The potential for mecamylamine to augment antidepressant drug action was also investigated. Sub-threshold and threshold doses of citalopram (3 and 10 mg/kg) or reboxetine (3, 10 and 20 mg/kg) were tested alone and in combination with nicotine (0.3 and 1.0 mg/kg) and mecamylamine (1 and 3 mg/kg). Locomotor activity experiments were performed to rule out non-specific stimulant effects. Nicotine (1.0 mg/kg) enhanced the effect of 10 mg/kg citalopram and 20 mg/kg reboxetine in the mFST. Similarly, nicotine (1.0 mg/kg) enhanced the effect of 3 and 10 mg/kg citalopram and 3 and 10 mg/kg reboxetine in the mTST. No concomitant locomotor stimulation was observed at the tested dose combinations. Mecamylamine was effective on its own in some tests, but did not augment the effects of citalopram or reboxetine at the doses tested. The data show that nicotine enhances the effects of both serotonin and noradrenaline reuptake inhibitors, possibly reflecting nicotine’s facilitating effects on the release of these two neurotransmitters, and indicating that nicotine may enhance antidepressant action.