Electrophysiological Studies on the Mechanism of Neuroleptanalgesia in the Central Nervous System Part I

Abstract

In an attempt to clarify the mechanism of neuroleptanalgesia in the central nervous system, changes were studied of the thresholds of arousal reaction and evoked m uscular discharge following stimuli on the rabbit brain stem reticular formation.
1) The threshold of arousal reaction following stimulation a t 100 Hz of the brain stem reticular formation resulted in increase by administration of droperidol or fentanyl citrate. When droperidol and fentanyl citrate were administered in combination at a ratio of 50 1the threshold showed a marked elevation over a single administration. The rate of increase in the threshold of combined administration revealed about the added sum of single administration.
2) The threshold of evoked muscular discharge of the fore and hind limbs following stimulation at 100 Hz of the brain stem reticular formation resulted in increase by administration of droperidol or fentanyl citrate. The combined administration likewise led to increase in the threshold of muscular discharge, but in a less degree than in arousal reaction.
3) The type of muscular discharge following stimulation of the brain stem reticular formation was generally a tonic type or a tonic phasic type in the fore limb, and a tonic phasic type in the hind limb. Administration of droperidol or fentanyl citrate or both resulted in few changes in the type of muscular discharge.
4) Since the combined administration inhibited arousal reaction to a considerable degree, it seemed favorable to be used in operation, considering increase of the threshold of arousal reaction. It did not show so strong an inhibition of muscular discharge so that a discussion was made as to the necessity of simultaneous use of muscle relaxants in operation.