Different susceptibilities of long-term potentiations in CA3 and CA1 regions of guinea pig hippocampal slices to nootropic drugs.

Effects of the nootropic drugs, piracetam and bifemelane, on long-term potentiation (LTP) of population spikes in the CA3 and CA1 regions of guinea pig hippocampal slices were investigated. Piracetam (10(-6) to 10(-4) M) and bifemelane (10(-8) to 10(-6) M) significantly augmented the LTP in the CA3 region. The effects of these drugs were inhibited by scopolamine (10(-6) M). However, the LTP in the CA1 region was not affected by piracetam and bifemelane even at highly effective concentrations (10(-5) and 10(-6) M, respectively). Thus, the LTP in the CA3 is more susceptible to nootropic drugs than in the CA1.