Responses of Primary Afferent Fibers to Acupuncture-Like Peripheral Stimulation at Different Frequencies: Characterization by Single-Unit Recording in Rats
1 Neuroscience Research Institute, Peking University, Beijing 100191, China
2 Department of Neurobiology, Peking University School of Basic Medical Sciences, Beijing 100191, China
3 Key Laboratory for Neuroscience, Ministry of Education/ National Health and Family Planning Commission, Peking University, Beijing 100191, China
4 Department of Radiology, Peking University Third Hospital, Beijing 100191, China
5 Department of Integration of Chinese and Western Medicine, Peking University School of Basic Medical Sciences, Beijing 100191, China
Abstract
The pain-relieving effect of acupuncture is known to involve primary afferent nerves (PANs) via their roles in signal transmission to the CNS. Using single-unit recording in rats, we characterized the generation and transmission of electrical signals in Aβ and Aδ fibers induced by acupuncture-like stimuli. Acupuncture-like signals were elicited in PANs using three techniques: manual acupuncture (MAc), emulated acupuncture (EAc), and electro-acupuncture (EA)-like peripheral electrical stimulation (PES). The discharges evoked by MAc and EAc were mostly in a burst pattern with average intra-burst and inter-burst firing rates of 90 Hz and 2 Hz, respectively. The frequency of discharges in PANs was correlated with the frequency of PES. The highest discharge frequency was 246 Hz in Aβ fibers and 180 Hz in Aδ fibers. Therefore, EA in a dense-disperse mode (at alternating frequency between 2 Hz and 15 Hz or between 2 Hz and 100 Hz) best mimics MAc. Frequencies of EA output >250 Hz appear to be obsolete for pain relief.
Keywords
Acupuncture; Peripheral electrical stimulation; Dorsal root; Primary afferent fiber; Electrophysiology; Single unit recording
