Muscarinic receptor activation facilitates the induction of long-term potentiation (LTP) in the rat dentate gyrus.

Bath application of two different concentrations of muscarine produced two different effects on evoked responses in the dentate gyrus of rat hippocampal slices. A concentration of 1 microM muscarine did not affect the evoked population spike or excitatory postsynaptic potential (EPSP), but facilitated the induction of LTP. In contrast, a concentration of 10 microM muscarine depressed both the population spike and EPSP, but had no effect on LTP induction. The M1 muscarinic receptor antagonist pirenzepine (1 microM) blocked the muscarine-induced facilitation of LTP, but had no effect on the depression of evoked responses. These data suggest that activation of M1 receptors can facilitate the induction of LTP.