Inhibition of electroacupuncture on nociceptive responses of dorsal horn neurons evoked by noxious colorectal distention in an intensity-dependent manner

Abstract

BackgroundThe transmission of visceral nociception can be inhibited by electroacupuncture (EA) at the spinal level. However, relationships between current intensity and EA-induced analgesia are still lacking. This study compares the effects of different intensities of EA at local acupoints and heterotopic acupoints on nociceptive responses of spinal wide dynamic range (WDR) neurons induced by noxious colorectal distension (CRD).Materials and methodsExperiments were conducted on 40 Sprague Dawley rats anesthetized with 10% urethane. Discharges of WDR neurons in the L1–L3 segments of the dorsal horn of the spinal cord were recorded extracellularly by glass micropipettes. Different intensities of EA (0.5, 1, 2, 4, 6, and 8 mA, 0.5 ms, 2 Hz) were applied to contralateral “Zusanli” (ST 36) or “Neiguan” (PC 6), with either the same or different segmental innervation of the colon.ResultsIn local acupoints, the increased discharges of WDR neurons evoked by CRD were significantly inhibited by EA at 0.5–8 mA. A positive relationship between current intensity and the inhibiting rate was observed within 0.5–4 mA, but the inhibiting rate reached a plateau when EA exceeded 4 mA. In heterotopic acupoints, the increased discharges of WDR neurons evoked by CRD were significantly inhibited by EA at 2–8 mA. A positive relationship between current intensity and the inhibiting rate was observed within 2–6 mA. Further increase in the current beyond 6 mA also resulted in a plateau effect.ConclusionWithin a certain range, the nociceptive responses of dorsal horn neurons induced by CRD could be inhibited by EA in an intensity-dependent manner.

Electroacupuncture-Induced Muscular Inflammatory Pain Relief Was Associated With Activation of Low-Threshold Mechanoreceptor Neurons and Inhibition of Wide Dynamic Range Neurons in Spinal Dorsal Horn

“…It was demonstrated that noxious and non-noxious stimuli elicited a progressive increase of WDR neurons response along with the increasing of stimulation intensity. The present study demonstrated that the analgesic effect of EA-Ta may be involved in the inhibition of WDR neurons in the spinal dorsal horn, which is consistent with previous reports ( Yu et al, 2019 ; Wang et al, 2020 ; Xue et al, 2020 ).…”

The Involvement of Central Noradrenergic Pathway in the Analgesic Effect of Bee Venom Acupuncture on Vincristine-Induced Peripheral Neuropathy in Rats

“…Furthermore, similar to the results of behavioral analyses (Figure 2), 1.0 mg/kg of BVA considerably protected rats from the neuronal hyperexcitation induced by vincristine (Figure 4). Growing evidence implies that the enhanced firing events of WDR neurons represent a state of pain [21,33,34], and therapy-induced decrement of these discharge rates means analgesia [35][36][37][38], indicating that our results could be promising therapeutic options for the clinical management of CIPN.…”

Effect of acupuncture on postoperative ileus after laparoscopic elective colorectal surgery: A prospective, randomised, controlled trial

“…In a study investigating the relationship between current intensity and EA-induced analgesia in rat with colorectal distension, the effect of EA at ST36 emerged from 0.5 mA, while the effect of EA at PC6 (like ST25, with different segmental innervation with colon) showed no significant difference until 2mA. 25 According to the treatment records, the average current intensity of the two EA groups was 1.5 mA, lower than the current intensity threshold of acupoints with different segmental innervation, which may explain why EA at ST25 did not work and is worthy of further study.…”