Synaptic potentials in cat's lateral geniculate neurons during natural sleep with special reference to paradoxical sleep.

Juxtacellular DC recordings from lateral geniculate body (LGB) relay cells were performed in completely undrugged cats during natural sleep. Paradoxical sleep (P) was characterized by a decrease in synaptic (S) potentials and an increase in spike discharge as compared to slow wave sleep. During the P grouped discharges simultaneous with eye movements and cortical waves, a further decrease in S potentials accompanied by an increased cell excitability as indicated by the higher probability to elicit an antidromic spike occurred. The results suggest that the decrease of S potentials in P is not the result of presynaptic inhibition but that most of them reach firing level during the P grouped discharges.