Abstract
Afferent pathways to cause acupuncture anesthesia was investigated by recording acupuncture stimulation-induced evoked potential in the brain.
The acupuncture stimulation was applied to the base of the ear which is known as an effective site to cause acupuncture anesthesia, and evoked potential was recorded through chronic implanted electrode in unanesthetized and unrestained rabbits.
Evoked potential was induced in the restricted dorsal part of the mesencephalic periaqueductal central gray (PAG), and the configuration of evoked potential was initial positive (P1) and negative (N1) waves.
The threshold stimulous intensity to cause evoked potential was that to cause muscle contraction of acupuncture stimulated point As increasing of stimulation intensity, the magnitude of evoked potential increased. When stimulous intensity increased to noxious one, later appearing positive (P2) and negative (N2) waves were induced. Intraperitonealy applied 10mg/kg morphine had almost no effect on configuration of evoked potential. Evoked potential was hardly induced by body acupunctural stimulation which was known as an uneffective site to cause acupuncture anesthesia. Other brain structures in which evoked potential was induced by acupuncture stimulation of ear base were centro-medial part of thalamus, septal nucleus, cingulate bundle and hippocampus which are pain motivational-affective dimension. Evoked potential was not recorded from caudate nucleus.
PAG stimulation also caused evoked potential in septal nucleus, cingulate bundle and hippocampus.
The sum of latency in evoked potential from PAG to cingulate bundle and from periphery to PAG is almost equal to that from periphery to cingulate bundle.
