title: Spinal Serotonergic and Opioid Receptors Are Involved in Electroacupuncture-Induced Antinociception at Different Frequencies on ZuSanLi (ST 36) Acupoint.
abstract: The present study was conducted to evaluate the effect of electroacupuncture-(EAc-) induced antinociception (EAA) at different currents and frequencies in rat spinal cord. We found that naloxone (0.05  μ g i.t.) blocked EAA at different frequencies. Naltrindole (0.05  μ g i.t.) blocked EAA on the 7th day after EAc of 100 Hz. 5,7-Dihydroxytryptamine (100  μ g i.t.) significantly inhibited EAA at different frequencies on the 7th day after EAc. Pindobind (0.5 μ g i.t.), a 5-HT1A antagonist, notably attenuated EAA at different frequencies. Ketanserin (0.5  μ g i.t.), inhibited EEA at a lower frequency (<10 Hz) than at a higher frequency (100 Hz). LY-278584 (0.5  μ g i.t.) significantly inhibited EAA at a higher frequency (100 Hz) on the 7th day after EAc. The direction of effect of 8-OH-DPAT, on EAA was dependent on dosage. It had an inhibitory effect at a low dose (0.5  μ g i.t.) and a high frequency (100 Hz) but enhanced EAA at a higher dose at lower frequencies (<10 Hz). DOI (10  μ g, i.t.), did not affect EAA. These data indicate that the mechanism of EAA involves opioid receptors, and the serotonergic system, particularly, μ -, δ -opioid and 5-HT1A, 5-HT3 receptors and it is also dependent on the EAc frequency.
authors.affiliation: Department of Neurology, Tzu Chi General Hospital, Taichung Branch, Taichung 42743, Taiwan ; Department of Medicine, College of Medicine, Tzu Chi University, Hualien 97002, Taiwan ; Department of Life Sciences, National Chung Hsing University, Taichung 40227, Taiwan.
authors.forename: Chi-Chung
authors.initials: CC
authors.lastname: Kuo
authors.forename: Huei-Yann
authors.initials: HY
authors.lastname: Tsai
authors.forename: Jaung-Geng
authors.initials: JG
authors.lastname: Lin
authors.forename: Hong-Lin
authors.initials: HL
authors.lastname: Su
authors.forename: Yuh-Fung
authors.initials: YF
authors.lastname: Chen