Effects of pentothal on neural activity in somatosensory cortex and brain stem in cat

Abstract

1. 1. By the use of microelectrode and evoked potential techniques, effects of pentothal (thiopental sodium) on neural activity in the somatosensory cortex and the brain stem were studied. 2. 2. A clear-cut relation between the evoked slow potential and unit response is not proved either in the somatosensory cortex or in the mesencephalic reticular formation. 3. 3. The spontaneous firing of a neuron is the most sensitive component to pentothal anaesthesia. It is first to be affected with a small dose of this drug while the unit response to peripheral stimulation still persists. This is equally true for cortical and brain stem neurons. 4. 4. When the spike train of unit response is examined under the action of pentothal, the spikes which are suppressed are those occurring in the later phases of the train, while the early occurring spikes may persist unchanged. 5. 5. The sensitivity to pentothal of the unit response elicited by peripheral stimulation is a function of the latency of the very first spike of the response. The shorter the latency, the more resistant the unit response is to pentothal. This is true in the mesencephalic reticular formation as well as in the lemniscal system.