NICOTINIC RECEPTOR AGONISTS EXHIBIT ANXIOLYTIC-LIKE EFFECTS ON THE ELEVATED PLUS-MAZE TEST

The effects of nicotinic receptor agonists on the elevated plus-maze t est of anxiety were investigated in CD1 mice after intraperitoneal inj ections. Nicotine and lobeline, but not cytisine, exhibited a signific ant increase in the time spent by the mice in the open arms, a measure of anxiolytic activity. Nicotine also increased the total number of a rm entries, a measure of general activity, but this effect was seconda ry to its anxiolytic-like properties. Nicotinic receptor antagonists o n their own did not modify the behavior of mice in the maze. The effec t of nicotine was mediated by central nicotinic receptors as it was bl ocked by the centrally-acting nicotinic antagonists mecamylamine and c hlorisondamine, but not by hexamethonium (a peripherally acting blocke r). Cotinine, the major metabolite of nicotine, was evaluated at diffe rent times after systemic injections and had no effect in the plus-maz e. The anxiolytic-like profile induced by nicotinic receptor stimulati on was not associated with potentiation of alcohol effects, a liabilit y associated with the benzodiazepine therapy. This study demonstrates the anxiolytic-like properties of nicotine and lobeline in mice, and s uggests that central nicotinic receptors are involved in the expressio n of emotional behavior.