In vitro extracellular recording of spontaneous activity of the intergeniculate leaflet neurons

In the view of importance of intergeniculate leaflet in circadian rhythms processes and lack of information about electrophysiological properties of isolated intergeniculate leaflet (IGL) neurons, we carried out extracellular recordings of the spontaneous activity of rat IGL cells in vitro. Unlike other structures of visual thalamus, IGL neurons have the ability to generate a robust spontaneous neuronal activity when maintained in vitro. We have observed that in a standard incubation fluid IGL neurons display at least three distinct firing patterns: continuously irregular-with a wide variety of firing rates, tonic-with a very stable level of activity, and phasic (slow bursts)-with intermittent silent periods. Our study is the first electrophysiological demonstration of IGL neuronal activity in vitro.