Abstract
BackgroundAcupuncture is a therapy that involves applying mechanical stimulation to acupoints using needles. Although acupuncture is believed to trigger neural regulation by opioids or adenosine, still little is known about how physical stimulation is turned into neurological signaling. The transient receptor potential vanilloid receptors 1 and 4 (TRPV1 and TRPV4) and the acid-sensing ion channel 3 (ASIC3) are regarded as mechanosensitive channels. This study aimed to clarify their role at the Zusanli acupoint (ST36) and propose possible sensing pathways linking channel activation to neurological signaling.MethodsFirst, tissues from different anatomical layers of ST36 and the sham point were sampled, and channel expressions between the two points were compared using western blotting. Second, immunofluorescence was performed at ST36 to reveal distribution pattern of the channels. Third, agonist of the channels were injected into ST36 and tested in a mouse inflammatory pain model to seek if agonist injection could replicate acupuncture-like analgesic effect. Last, the components of proposed downstream sensing pathway were tested with western blotting to determine if they were expressed in tissues with positive mechanosensitive channel expression.ResultsThe results from western blotting demonstrated an abundance of TRPV1, TRPV4, and ASIC3 in anatomical layers of ST36. Furthermore, immunofluorescence showed these channels were expressed in both neural and non-neural cells at ST36. However, only capsaicin, a TRPV1 agonist, replicated the analgesic effect of acupuncture when injected into ST36. Components of calcium wave propagation (CWP, the proposed downstream sensing pathway) were also expressed in tissues with abundant TRPV1 expression, the muscle and epimysium layers.ConclusionsThe results demonstrated mechanosensitive channel TRPV1 is highly expressed at ST36 and possibly participated in acupuncture related analgesia. Since CWP was reported by other to occur during acupuncture and its components were shown here to express in tissues with positive TRPV1 expression. These findings suggest TRPV1 might act as acupuncture-responding channel by sensing physical stimulation from acupuncture and conducting the signaling via CWP to nerve terminals. This study provided a better understanding between physical stimulation from acupuncture to neurological signaling.
Highlights
Acupuncture is a therapy that involves applying mechanical stimulation to acupoints using needles
Manual acupuncture had an analgesic effect at ST36 but not at the sham point Before demonstrating the existence of mechanosensitive channels at ST36, it is important to make sure that ST36 and the sham point defined were truly a functional acupoint and a nonfunctional sham point, respectively
The results showed that 60 min after Manual acupuncture (MA) at ST36 on day 3 (D3), thermal hyperalgesia was significantly reduced compared with that observed before MA because the withdrawal latency ratio increased from 0.71 ± 0.04 to 0.91 ± 0.07 (P < 0.05; Mann–Whitney rank sum test) (Figure 2A)
Summary
Acupuncture is a therapy that involves applying mechanical stimulation to acupoints using needles. Acupuncture is an ancient therapy that gained worldwide acknowledgment in recent decades [1] It involves inserting needles into acupoints followed by manual manipulation (manual acupuncture, MA) or electrostimulation (electroacupuncture, EA) to induce its therapeutic effect in epilepsy, [2] stroke, [3] and pain treatment [4,5,6]. ATP is metabolized to antinociceptive adenosine by prostatic acid phosphatase in muscles, resulting in analgesia This finding was further augmented by reduced acupuncture analgesia in adenosine A1 receptor knockout mice. These results demonstrated that acupuncture is related to local ATP release and subsequent neural regulation. It remains unknown how mechanostimulation from acupuncture induces ATP release and neural stimulation
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have