Does barbiturate anesthesia modify the neuronal properties of the somatosensory thalamus? A single-unit study related to nociception in the awake-pentobarbital-treated rat.

By means of extracellular recordings, we studied thalamic ventrobasal complex neurons of rats tested first awake, and then anesthetized with pentobarbital. In both conditions, we found two groups of units in both states. The first group, displaying a spontaneous bursting activity, was not obviously responding to peripheral stimuli. Another group, displaying a single-spike activity, was almost exclusively activated by innocuous and/or noxious and innocuous mechanical stimuli. Still in this group, units specifically driven by noxious stimuli were only found under pentobarbital. These data, different from classical findings, emphasize the interest of the awake preparation in order to study nociceptive cellular mechanisms at the thalamic level.