POSTNATAL-DEVELOPMENT OF CHOLINERGIC PRESYNAPTIC INHIBITION IN RAT HIPPOCAMPUS

Muscarinic depression of field potential excitatory postsynaptic poten tials (fEPSPs) in stratium radiatum of area CA1 was compared in hippoc ampal slices from rats of different ages. Bath application of 4 muM mu scarine reversibly depressed the fEPSP slope by 68.4% in slices from a dult animals (P43-P60), but caused only a 32.2% depression in slices f rom P5-P7 animals. The magnitude of the depression increased with age during the first postnatal month. Reduced sensitivity of excitatory sy naptic transmission to cholinergic depression during postnatal develop ment could be one factor contributing to the hyperexcitability of imma ture hippocampus.