A possible involvement of monoaminergic and opioidergic systems in the analgesia induced by electro-acupuncture in rabbits.
To elucidate mechanisms involved in analgesia induced by effects of electro-acupuncture (EAP), effects of EAP on evoked potentials and release of substance P (SP) following tooth pulp stimulation (ST) in the superficial layers of the trigeminal nucleus caudalis (Vc-I-II) were studied in the rabbit. The potentials evoked by ST were composed of two main components with conduction velocity of ca. 30 m/sec (fast component) and ca. 12 m/sec (late component). The late component was significantly inhibited by morphine (10 mg/kg, i.v.) or CP-96,345 (5 mg/kg, i.v.), an SP antagonist. This inhibitory effect of morphine was antagonized by naloxone (1 mg/kg, i.v.) or methysergide (5 mg/kg, i.v.). In addition, the late component was significantly inhibited by EAP, which was observed in ca. 70% of the rabbits examined. This EAP-induced inhibitory effect was antagonized by naloxone (1 mg/kg, i.v.) or methysergide (5 mg/kg, i.v.), but not by prazosin (5 mg/kg, i.v.) and yohimbine (1 mg/kg, i.v.). The stimulus-evoked SP release was inhibited by EAP, which was significantly antagonized by pretreatment with naloxone (1 mg/kg, i.v.) or methysergide (5 mg/kg, i.v.). These results suggest that one of the mechanisms of analgesia induced by EAP is due to inhibition of the stimulus-evoked SP release in the Vc-I-II through activation of the descending serotonergic systems linking up with opioidergic systems.
Takagi
J
J
Department of Anesthesiology, Osaka University Faculty of Dentistry, Japan.
Sawada
T
T
Yonehara
N
N
D015667:Acupuncture Analgesia; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D015306:Biogenic Monoamines / Q000378:metabolism*; D001713:Biphenyl Compounds / Q000494:pharmacology; D003782:Dental Pulp / Q000502:physiology; D015671:Electroacupuncture; D005071:Evoked Potentials / Q000187:drug effects; D006993:Hypnotics and Sedatives / Q000494:pharmacology; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D009020:Morphine / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009431:Neural Conduction / Q000187:drug effects; D018847:Opioid Peptides / Q000378:metabolism*; D011817:Rabbits; D012701:Serotonin / Q000378:metabolism; D012702:Serotonin Antagonists / Q000494:pharmacology; D013373:Substance P / Q000378:metabolism; D014278:Trigeminal Nuclei / Q000187:drug effects / Q000378:metabolism / Q000502:physiology
D000701:Analgesics, Opioid; D015306:Biogenic Monoamines; D001713:Biphenyl Compounds; D006993:Hypnotics and Sedatives; D009292:Narcotic Antagonists; D018847:Opioid Peptides; D012702:Serotonin Antagonists; D012701:Serotonin; D013373:Substance P; D009270:Naloxone; D009020:Morphine; C066892:CP 96345; D008784:Methysergide