[The role of negative feedback modulating pain of nucleus raphe magnus in electroacupuncture analgesia].
In recent years I am interested in the role of nucleus raphe magnus (NRM) in acupuncture analgesia, NRM is the one of important descending inhibitory systems included in the intrinsic analgesic systems in brain, and we gave more systematic study on the question. The primary results are as follows: 1. Experiments were performed on male rats, unit discharges of NRM were recorded extracellularly with glass electrode. The neurons respond to noxious stimulation were chosen to observe analgesia of EA. The spontaneous firing rates of NRM neurons were about 0.5-20 Hz, a few of them over 20Hz or have no any discharges. NRM neurons have not often responses to nonnoxious stimulation (to brush hair) or only have a light responses and adaptation appeared fast. But responses of them to noxious stimulation (to clamp or to prick skin) or electro-stimulation (over 6V) were obviously displayed with excitatory (increasing firing rates) or inhibitory (decreasing) types. The spontaneous firing rates of excitatory NRM neurons were lower than that of inhibitory neurons. In addition, a few excitatory-inhibitory reversible type NRM neurons were found unexpected, and the reversal of response were related to background firing rates. During low firing rates, the response was an excitatory one, and during high firing rates, it became an inhibitory one. 2. EA of 'Zusanli' could activate NRM neurons, increasing spontaneous firing rates, and inhibit their nociceptive responses. The effect induced by EA could be reversed by naloxone (I.P.). 3. Raphe-spinal neurons in NRM were identified by antidromic activation and collision technology, their axons project to dorsal horn of spinal cord via dorsal lateral fasciculus (DLF), that seem to be centrifugal units.(ABSTRACT TRUNCATED AT 250 WORDS)
Liu
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Institute of Acupuncture and Moxibustion, China Academy of Traditional Chinese Medicine, Beijing.
D015667:Acupuncture Analgesia; D000818:Animals; D015671:Electroacupuncture; D005246:Feedback; D006801:Humans; D009474:Neurons / Q000502:physiology; D009619:Nociceptors / Q000502:physiology; D010146:Pain / Q000503:physiopathology; D011903:Raphe Nuclei / Q000502:physiology*