Hippocampus
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The cellular-synaptic generation of rhythmic slow activity (RSA or theta) in the hippocampus has been investigated by intracellular recording from principal cells and basket cells in anesthetized rats. In addition, the voltage-, coherence-, and phase versus depth profiles were examined by simultaneously recording field activity at 16 sites in the intact rat, during urethane anesthesia, and after bilateral entorhinal cortex lesion. In the extracellular experiments the large peak of theta at the hippocampal fissure was attenuated by urethane anesthesia and abolished by entorhinal cortex lesion. ⋯ Basket cells possessed the most regular membrane oscillations of the three cell types. All neurons of this study were verified by intracellular injection of biocytin. The observations provide direct evidence that theta-related rhythmic hyper-polarization of principal cells is brought about by the rhythmically discharging basket neurons.(ABSTRACT TRUNCATED AT 250 WORDS)