NICOTINE INCREASES INTRACELLULAR CALCIUM IN RAT HIPPOCAMPAL-NEURONS VIA VOLTAGE-GATED CALCIUM CHANNELS

The effect of nicotinic receptor activation on intracellular calcium concentrations ([Ca2+](i)) was quantitated in populations of cultured hippocampal neurons loaded with Fura-2. Nicotine (50 mu M) and cytisine (50 mu M) increased [Ca2+](i) by 100%. This response was abolished in the presence of the nicotinic antagonist methyllycaconitine (MLA) whereas KCl-evoked increases in [Ca2+](i) were insensitive to MLA. Glial cultures were unaffected by nicotine, although they did respond to glutamate with increased [Ca2+](i). In hippocampal neurons, responses to nicotinic agonists and KCl were dependent on the presence of extracellular Ca2+ and were similarly sensitive (85% inhibition) to CdCl2. These results are consistent with the presence of functional nicotinic receptors on hippocampal neurons. The receptors appear to elevate [Ca2+](i) by promoting the influx of extracellular Ca2+ through voltage-gated calcium channels.