Abstract
It have been demonstratd previously by studies of our department that the electrical stimuration of the ventromedian nucleus of the hypothalamus (HVM) produced analgesia, which was partially abolished by lesion of the ventral part of the peri-aqueductal central gray (V-PAG), and that stimulation-produced-analgesia of the V-PAG (V-PAG-SPA) was mediated by the serotonergic descending inhibitory system (DPIS) . However it has not been studied the imvolvement of the adrenergic mechanism in HVM-SPA. The present study was undertaken to investigate whether nucleus paragigantocellularis (NRPG) and parabrachium conjunctivum (PBC) are involved in the acupuncture analgesia (AA) as the noradrenergic DPIS. Analgesia was measured by tail flick latency of the rats. Brain was stimulated by chronically inserted stainless-steel attached elecrodes to the HVM, V-PAG and PBC. Drugs were administrated by intrathecal catheter to the intrathecal space. As the results, the followings were found. Lesion of the HVM abolished AA. Electrical stimulation of the HVM produced analgesia (HVM-SPA) . HVM-SPA was abolished partially by lesion of the NRPG. Evoked potential was produced in the NRPG by HVM stimulation. Stimulation of the NRPG produced analgesia which was limitted during stimulation and was not exhibit individual variation in effectiveness. These properties of NRPG-SPA are the nature of SPA of the DIPS. NRPG-SPA was antagonized compleately by intrathecal administration of 20μg of the phentolamine, but it was not influened by administration of intrathecal 20μg or intraperitonial 2mg of methylsergide. Lesion of the PBC did not abolished AA as well as V-PAG-SPA. Stimulation of the PBC produced analgesia. It was concluded from these results that the NRPG play a role in producing the part of HVM-SPA as the noradrenergic DPIS in acupuncture analgesia. Although stimulation of the PBC produced analgesia, but PBC did not relate to AA, since PBC lesion did not inenfluce on A A.
