Strain-selective effects of nicotine on electrophysiological responses evoked in hippocampus from DBA/2Ibg and C3H/2Ibg mice.

We used the hippocampal slice to examine extracellular electrophysiological responses to nicotine and the difference in sensitivity to nicotine-induced electrophysiological effects between the DBA and C3H mouse strains. Nicotine enhanced CA1 population spikes (PS) evoked by Schaffer collateral stimulation in a concentration-dependent manner (100 microM to 3.2 mM). This enhancement was slow to appear, achieving a maximum after 15 min. The enhanced PS was accompanied by the development of epileptiform activity (multiple PS's) at nicotine concentrations greater than or equal to 400 microM. Slices from DBA mice were significantly more sensitive than those from the C3H strain to these electrophysiological effects of nicotine. Mecamylamine (400 microM) blocked both the nicotine-induced PS enhancement and secondary population spikes in both strains, suggesting the involvement of nicotinic cholinergic receptors.