title: Limbic neuronal firing rates in man during administration of nitrous oxide--oxygen or sodium thiopental.
abstract: Electroencephalographic activity and extracellular discharges from neurons in deep temporal lobe structures were recorded from fine wire microelectrodes chronically implanted in seven psychomotor epileptic patients for diagnostic localization of seizure foci. In four patients, inhalation of 80 per cent nitrous oxide resulted in loss of consciousness without change in firing rates of temporal lobe neurons (n = 22). In all seven patients, thiopental (400 or 200 mg, iv) decreased limbic neuronal firing rates (n = 38) until the return of wakefulness. In only three of these patients, however, did the firing rates of the neurons (n = 19) decrease significantly (P less than .05). Thiopental suppression of unit activity was not related to systemic hypoxia. This study demonstrates that anesthetic induction with nitrous oxide-oxygen does not significantly affect the firing of neurons in various regions of the human limbic system, which may explain the incidence of patient awareness reported when nitrous oxide-oxygen is administered alone. Thiopental depresses the firing of limbic neurons, and this may account in part for the temporary confusion and amnesia often manifested by patients recovering from the effects of thiopental.
mesh_terms: D000293:Adolescent; D000328:Adult; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis / Q000503:physiopathology; D006801:Humans; D008032:Limbic System / Q000187:drug effects* / Q000503:physiopathology; D009431:Neural Conduction; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D009609:Nitrous Oxide; D009435:Synaptic Transmission; D013874:Thiopental
chemical_list: D013874:Thiopental; D009609:Nitrous Oxide