Effects of nicotine, pilocarpine, and tetrahydroaminoacridine on hippocampal theta waves in freely moving rabbits.

The effects of three cholinergic agents on hippocampal theta waves were investigated by analyzing electroencephalographic power spectra in freely moving rabbits. In the hippocampal spectra, nicotine (a nicotinic receptor agonist, 0.03 mg/kg) increased the theta wave frequency, but caused no change in its power. Pilocarpine (a muscarinic receptor agonist, 0.3 and 1.0 mg/kg) and tetrahydroaminoacridine (a cholinesterase inhibitor, 3.0 mg/kg) increased the power and deceased the frequency. These results suggest that the activating effect of nicotinic receptor agonists on the hippocampus may be different from that of muscarinic receptor agonists or cholinesterase inhibitors.