A test of the cognitive-enhancing potential of low-dose mecamylamine in healthy non-smokers.

RATIONALE: The beneficial effects of nicotinic acetylcholine receptor (nAChR) agonists on cognitive performance have been widely shown. Paradoxically, recent preclinical studies employing extremely low doses of nAChR antagonists have also found cognitive enhancement, perhaps pointing to a novel treatment mechanism for cognitive deficits.

OBJECTIVES: The aim was to test whether low doses of the nAChR antagonist mecamylamine would benefit performance in human volunteers.

METHODS: The study employed a double-blind within-subject design. Over four separate days, healthy adult non-smokers (n = 23) were tested with placebo and three trace doses of mecamylamine (0.25-1 mg, p.o.), adjusted for body weight. Participants performed three computerized tasks: a task of spatial selective attention and stimulus detection, the rapid visual information processing task (RVIPT) taxing sustained attention and working memory, and a change detection short-term memory task. Subjective state and vital signs were assessed repeatedly.

RESULTS: Mecamylamine did not improve performance in any of the tasks. Any trends that were observed instead pointed toward performance impairment. Mecamylamine also had no effects on subjective state or vital signs.

CONCLUSIONS: The present results do not support the hypothesized cognitive-enhancing potential of low doses of mecamylamine. Contrary to preclinical reports, these findings speak against low-dose nAChR antagonism as a novel avenue for treating cognitive deficits.