Oscillatory potentials of the cat lateral geniculate nucleus induced by barbiturate

1. An orderly sequence in which the spontaneous electrical activity of the lateral geniculate nucleus (LGN) changes to a rhythmic one after intravenous administration of thiopental was studied in cats. 2. The response of LGN to barbiturate differed greatly from those of other thalamic specific nuclei. After administration of barbiturate, there appeared in the LGN a series of oscillatory potentials (barbiturate oscillatory potentials; BO potentials), the frequency of which changed sequentially from an initial 40 HZ to 10, 10, 5, and finally, 2.5 HZ. 3. Frequency changes of BO potentials in the LGN were observed only when the retinas were intact. Following destruction of bilateral retinas, the LGN responded to barbiturate with spindle activity as did other thalamic nuclei. 4. Depth potential analysis of the LGN activities showed that the BO potentials were generated in layers A and A1. By contrast, the spindle activity was recorded mainly from layer B. 5. Simultaneous recordings from the LGN and the optic nerve indicated that the BO potentials in the LGN were driven by retinal afferent discharges.