Differentiation of acupuncture and nonacupuncture points by difference of associated opioids in the spinal cord in production of analgesia by acupuncture and nonacupuncture point stimulation, and relations between sodium and those opioids.

Antiserum of methionine-enkephalin (Met-Enk) applied intrathecally abolished acupuncture analgesia (AA) caused by low frequency stimulation of an acupuncture point (tibial muscle, APS) of rats, but antisera of leucine-enkephalin (Leu-Enk) and dynorphin (Dyn) did not. Antiserum of Dyn applied intrathecally abolished analgesia (NAA) produced by stimulation of a nonacupuncture point (NAPS) which was revealed by lesion in the analgesia inhibitory system (AIS), whereas antisera of Met-Enk and Leu-Enk did not. NAA was antagonized by the kappa-receptor antagonist, Mr2266, and analgesia was produced by the kappa-agonist, U50-488H, in the AIS lesioned rats. Potentials in the dorsal periaqueductal central gray (D-PAG) evoked by APS were antagonized by naloxone and antiserum of Met-Enk, and those in the lateral PAG (L-PAG) evoked by NAPS were antagonized by Mr2266 and antiserum of Dyn. After adrenalectomy, AA, potentials in the D-PAG, and analgesia caused by stimulation (SPA) of the D-PAG were abolished 12 hour; and NAA, potentials in the L-PAG, and SPA of the L-PAG were abolished in 24 hour. All were then restored one hour after intravenous application of 1 ml of 5% NaCl solution. AA and NAA which were augmented for several hours before their abolition after adrenalectomy were not antagonized by naloxone nor M 2266, respectively. However naloxone and Mr2266 did antagonize AA and NAA, respectively, one hour after treatment with 1 ml of 5% NaCl solution.