Postnatal development of cholinergic presynaptic inhibition in rat hippocampus.

Muscarinic depression of field potential excitatory postsynaptic potentials (fEPSPs) in striatum radiatum of area CA1 was compared in hippocampal slices from rats of different ages. Bath application of 4 microM muscarine reversibly depressed the fEPSP slope by 68.4% in slices from adult animals (P43-P60), but caused only a 32.2% depression in slices from P5-P7 animals. The magnitude of the depression increased with age during the first postnatal month. Reduced sensitivity of excitatory synaptic transmission to cholinergic depression during postnatal development could be one factor contributing to the hyperexcitability of immature hippocampus.