Effect of scopolamine and HP 029, a cholinesterase inhibitor, on long-term potentiation in hippocampal slices of the guinea pig

The effect of scopolamine and a cholinesterase inhibitor on long-term potentiation (LTP) of population spikes was studied in a guinea pig hippocampal slice preparation. After brief application of each drug (10 min), LTP in CA1 and CA3 was induced by tetanus stimulation delivered to commissural/associational fibers and mossy fibers, respectively. Scopolamine at concentration of 10 microM had no effect on LTP in CA1 but significantly suppressed LTP in CA3. The cholinesterase inhibitor, 9-amino-1,2,3,4-tetrahydroacridine-1-ol maleate (HP 029) at concentration of 10 microM significantly enhanced LTP both in CA1 and CA3. These results suggest that the cholinergic system is involved in producing LTP in CA3. Another mechanism of the effect of HP 029 on LTP in CA1 is discussed.