Convergence from the preoptic area and arcuate nucleus to the median eminence in acupuncture and nonacupuncture point stimulation analgesia.

Lesion of the preoptic area (POA) or medial arcuate nucleus (M-HARN) abolished acupuncture analgesia (AA). Potentials in the median eminence (ME) evoked by stimulation of the acupuncture point (AP) were not affected by lesion of either the POA or M-HARN alone, but were abolished by concurrent lesion of both. No analgesia was produced by stimulation of the POA. Analgesia produced by stimulation of the M-HARN was abolished by lesion of the POA, and the abolished analgesia was restored by concurrent stimulation of the POA and M-HARN, hence POA and M-HARN outputs might converge in the ME to produce AA. Similar convergence from the anterior arcuate nucleus (A-HARN) and POA to the ME was observed in analgesia (NAA) produced by stimulation of a nonacupuncture point (NAP). Two pathways diverged from the lateral hypothalamus in the AA afferent pathway and two from the lateral periaqueductal central gray (L-PAG) in the NAA afferent pathway. POA potentials evoked by stimulation of the AP were reversed by naloxone, and those evoked by stimulation of the AP were reversed by dexamethasone. ACTH sensitive sites were found in both the L-PAG and the anterior hypothalamus.