Spinal Serotonergic and Opioid Receptors Are Involved in Electroacupuncture-Induced Antinociception at Different Frequencies on ZuSanLi (ST 36) Acupoint
Schedule of drug treatment and experiment orders. Stable TF latency was carried out firstly before the surgery. EAc was performed 3 hrs after the rat recovered from ether anesthesia postintrathecal (i.t.) cannulation. Acupuncture was performed by inserting fine stainless acupuncture needles at bilateral acupoints ZuSanLi (ST36). EAc was applied with different currents (1 mA, 2 mA, and 3 mA) and different frequencies (2 Hz, 10 Hz, and 100 Hz) for 10 min, which was performed with electric stimulator. 1 mA current was chosen for the subsequent experiments in which drugs administration was held before electroacupuncture in this study. The pain threshold was determined by tail-flick Analgesia Meter. The basal TF latencies were typically between 2 and 4 seconds. EAc: electroacupuncture; *TF: tail-flick; 5,7-DHT: 5,7-dihydroxytryptamine, one week prior to EAc.