Entorhinal activation of dentate granule cells.

Abstract

AbstractIn rabbits, anesthetized with urethane‐chloralose. the activation of the granule cells of the dentate area by perforant path fibres from the entorhinal area was studied by intracellular and extracellular recording. Intracellular recording showed that the perforant path produced a large EPSP in the granule cells, followed after 2–4 msec by a large IPSP, lasting some 100 msec. Field potential studies indicated that the synapses responsible for the EPSP were located on the middle third of the dendritic tree, whereas the IPSP was generated by synapses at, or very close to, the cell bodies. The most likely explanation is that the inhibition is mediated by a recurrent inhibitory pathway, in which the collaterals of the granule cell axons excite the basket cells These are inhibitory in nature and send their axons to terminate upon the somata of many granule cells. The inhibition of the granule cells produced by the perforant path is resistant to strychnine in doses up to 0.6 mg/kg. The efficiency of the perforant path excitatory synapses was greatly increased by raising the rate of stimulation from 1 to 10 a second.