Research Article Effects of Electroacupuncture of Different Frequencies on the Release Profile of Endogenous Opioid Peptides in the Central Nerve System of Goats

Copyright © 2012 Li-Li Cheng et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. To investigate the release profile of met-enkephalin, β-endorphin, and dynorphin-A in ruminants ’ CNS, goats were stimulated by electroacupuncture of 0, 2, 40, 60, 80, or 100Hz for 30min. The pain threshold was measured using potassium iontophoresis. The peptide levels were determined with SABC immunohistochemisty. The results showed that 60Hz increased pain threshold by 91%; its increasing rate was higher (P < 0.01) than any other frequency did. 2Hz and 100Hz increased met-enkephalin immunoactivities (P < 0.05) in nucleus accumbens, septal area, caudate nucleus, amygdala, paraventricular nucleus of hypothalamus, periaqueductal gray, dorsal raphe nucleus, and locus ceruleus. The two frequencies elicited β-endorphin release (P < 0.05) in nucleus accumbens, septal area, supraoptic nucleus, ventromedial nucleus of hypothalamus, periaqueductal gray, dorsal raphe nucleus, locus ceruleus, solitary nucleus and amygdala. 60Hz increased (P < 0.05) met-enkephalin or β-endorphin immunoactivities in the nuclei and areas mentioned above, and habenular nucleus, substantia nigra, parabrachial nucleus, and nucleus raphe magnus. High frequencies increased dynorphin-A release (P < 0.05) in spinal cord dorsal horn and most analgesia-related nuclei. It suggested that 60Hz induced the simultaneous release of the three peptides in extensive analgesia-related nuclei and areas of the CNS, which may be contributive to optimal analgesic effects and species variation. 1