Spontaneous activity mediated by NMDA receptors in immature rat entorhinal cortex in vitro

Intracellular recordings were made from cells in layer II of entorhinal cortex slices from 9 to 13-day-old rats. The majority of these cells showed pronounced spontaneous synaptic activity which could summate into large depolarizing events and give rise to bursts of spikes. These events could be associated with an apparent decrease in membrane conductance. They were reduced in amplitude by hyperpolarization of the cell and tended to increase on depolarization. Perfusion with 2-amino-5-phosphonovalerate abolished the spontaneous activity. Thus, in layer II of the entorhinal cortex at this stage of development there seems to be a functional enhancement of ongoing synaptic activity mediated via activation of N-methyl-D-aspartate receptors.