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

Abstract

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 100 Hz for 30 min. The pain threshold was measured using potassium iontophoresis. The peptide levels were determined with SABC immunohistochemisty. The results showed that 60 Hz increased pain threshold by 91%; its increasing rate was higher (P < 0.01) than any other frequency did. 2 Hz and 100 Hz 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. 60 Hz 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 60 Hz 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.

Electroacupuncture Reduces Cocaine-Induced Seizures and Mortality in Mice

“…There were few reports in the literature as to the effects of EA 50 Hz as compared to those of EA 2 and 100 Hz. However, it has been recently reported that EA 60 Hz increases the pain threshold by a greater extent than any other frequency [87]. EA at a frequency of 60 Hz induced the simultaneous release of met-enkephalin, β -endorphin, and dynorphin-A in extensive analgesia-related nuclei and areas of the CNS, such as the periaqueductal gray, the paraventricular nucleus of the hypothalamus, the ventromedial nucleus of the hypothalamus, the dorsal raphe nucleus, and the nucleus raphe magnus, amongst others.…”

“…These results suggest that EA at 60 Hz may contribute to optimal analgesic effects. The effects of EA at 50 or 60 Hz deserve to be studied further [87]. …”

Electroacupuncture-Induced Dynamic Processes of Gene Expression Levels of Endogenous Opioid Peptide Precursors and Opioid Receptors in the CNS of Goats

“…At 0.5 h before and at 0, 2, 4, 6, 8, 12, and 24 h after EA, the pain threshold was measured on the center of the left flank using the method of potassium iontophoresis as described in detail by Cheng et al [16]. The pain threshold in the sham control was measured at 0.5 h before needle insertion and at 0 h after needle withdrawal.…”

“…The goat's brain, hypophysis, and a part of the adjacent spinal cord were immediately taken out of the skull and cervical vertebral canal. The brain was transected into 17 sections quickly with the method described by Cheng et al [16]. The nuclei and areas were identified according to the photographic atlas of the goat brain and the morphological characteristics of the neurons [17–19].…”

“…The experimental goats were taken and anesthetized as above. According to the previous research results that opioid peptides in the CNS were released to the higher level at the end of EA [16], six sham control goats in this study were anesthetized and perfused immediately after needle withdrawal. The goats were fixed with the infusion of 4% paraformaldehyde through bilateral carotid arteries.…”