Involvement of the mechanoreceptors in the sensory mechanisms of manual and electrical acupuncture

The modalities of acupuncture can be broadly classified into manual acupuncture (MA) and electroacupuncture (EA). Although MA has been reported to cause winding of tissue around the needle and subsequent activation of the sensory mechanoreceptors and nociceptors, the sensory mechanisms of acupuncture stimulation are not fully understood. To test the hypothesis that the involvement of the mechanoreceptors in the sensory mechanism is different in MA and EA, we examined the effects of a stretch-activated channel blocker gadolinium on the hemodynamic responses to hind limb MA and EA in anesthetized rats (n = 9). Gadolinium significantly attenuated the MA-induced bradycardic response (− 22 ± 5 vs. − 10 ± 3 bpm, P < 0.05) and tended to attenuate the MA-induced depressor response (− 30 ± 5 vs. − 18 ± 4 mm Hg, P = 0.06). On the other hand, gadolinium significantly attenuated both the EA-induced bradycardic (− 22 ± 5 vs. − 9 ± 4 bpm, P < 0.01) and depressor responses (− 32 ± 6 vs. − 15 ± 5 mm Hg, P < 0.01). These results indicate that the mechanoreceptors are involved in the sensory mechanisms for both MA and EA.