NLA変法(modified neuroleptanalgesia)の中枢作用機序に関する電気生理学的研究

Abstract

An attempt was made to clarify the effects of the modified NLA on the central nervous system using Diazepam and Pentazocine. The unanesthetized rabbit was used as the experimental animal. The results obtained were as follows.1) Threshold of arousal reaction and evok ed muscular discharge rose more remarkably when Diazepam and Pentazocine were administered in the ratio of 1 to 3 than when either one of them was administered. This finding showed that the combination of the two agents had more inhibitory effect on consciousness and motor activity than either of them.2) Average threshold of arousal reaction in the hippocampus rose more rem arkably than in the cerebral cortex when the two agents were administered in the same way.3) Under the combination of the two agents, average threshold rose most remarkably in hind limbs, followed by fore limbs, the hippocampus and the cerebral cortex in this order.4) Under the combination of the two agents, threshold of evoked muscular d ischarge showed a marked elevation, about double the threshold of arousal reaction. This finding proved that the modified NLA had an inhibitory effect on the sensory nerve, and an even more powerful inhibitory effect on the motor nerve.5) Pentazocine showed as equally inhibitory effect as the combination of the two agents did on the early components of average evoked potential in the cerebral cortex. Consequently, it was clear that the effect on the afferent pathway was mostly attributed to Pentazocine.6) The late components (N4 and N5) of the average evoked potential in creased in the cerebral cortex under the combination of the two agents.7) The late components of the average evoked potential in the hippocampus were powerfully inhibited under the same condition. This finding made it clear that the combination of the two agents powerfully suppressed pain reaction.8) M and H waves showed no incre ase under the combination of the two agents, whereas they did with the administration of either one of them. This fact is advantageous to anesthetization in a surgical operation.9) The combina tion of the two agents showed powerful inhibition on the microvibration (MV).10) With regard to photopalpebral reflex (PPR), PPR6 showed an increase under the combination of the two agents.11) The rate of in crease of the threshold of arousal reaction and evoked muscular discharge diminished remarkably after the destruction of nucleus ventralis anterior (VA) under the combination of the two agents. This finding elucidated that the VA was concerned with the increase of the threshold of arousal reaction and evoked muscular discharge.12) The increase of N4, N5 and PPR6 under the combination of the two agents disappeared after the destruction of VA. It was therefore obvious that the increase of these responses was caused by excitement of the diffuse thalamocortical projection system.13) Recruiting response caused by excitement of the d iffuse thalamocortical projection system showed an increase under the combination of the two agents.14) The action potentials, VAN4 and VAN5, induced from the cerebral cortex by a 1Hz stimulation on the VA increased under the combination of the two agents. This finding led us to the conclusion that the increase in N4, N5 and PPR6 was a direct expression of the excitement of the diffuse thalamocortical projection system.