[The role of Ach in the central nerve system on pain modulation and analgesia]

This article reviews the main results in recent years of studies on the role of central Ach in pain modulation and analgesia, including: (1) cholinergically induced analgesia (CIA). Cholinomimetic drugs raised the pain threshold or inhibited the unit discharges of hypothalamus parafascicularis nuclens in rats, and these actions were revised by atropine not by nicotine. (2) Ach and acupuncture analgesia (AA). The effect of electroacupuncture was changed by administration of HC-3, atropine, etc. (3) Ach and stress analgesia (SA). Scopolamine reduced the hind foot shock induced analgesia, and this kind of SA was probably mediated by m-receptors existed at supraspinal, rather than spinal level. Swimming and immobilization analgesia were also related to Ach. These data suggested that the central cholinergic system is very important in pain modulation and analgesia and the central Ach is essential transmitter or modulator in this analgesic pathway. But the problem is whether the mechanism of CIA is involved in opiate analgesic system or not.