Activation of neuronal nicotinic acetylcholine receptors (nAChR) by nicotine has been suggested to protect neurons against a hypoxic insult. The objective of this study was to examine the nature of cell death induced by acute hypoxia in rat primary cortical cultures and the neuroprotective potential of nicotine in ameliorating these processes. Neuronal cell death induced by a 4-h exposure to hypoxia (0.1% O-2) was apoptotic, as shown by TUNEL staining and assays monitoring DNA strand breaks and caspase-3/7 activity. The presence of nicotine (10 muM) during the hypoxic insult protected a subpopulation of susceptible neurones against DNA damage and apoptosis induced by oxygen deprivation. This protective effect of nicotine was prevented by a 30-min pre-incubation with either 100 nM alpha-bungarotoxin or 1 muM dihydro-beta-erythroidine, but not 1 muM atropine, suggesting that activation of at least two subtypes of nAChR, alpha7 and beta2* nAChR, is involved in mediating nicotine neuroprotection.