Purpose: This study was aimed to investigate the effects of heat-conduction dry needling therapy on chronic myofascial pain syndrome (CMPS) in rats and explore the analgesic mechanisms by measuring the mRNA expression of transient receptor potential cation channel subfamily V member 1 (TRPV1) in musculus gastrocnemius.
Methods: Seventy-two rats were randomly divided into five groups. Group A was the control group containing eight normal rats. Group B was the model group where 16 rats developed CMPS in musculus gastrocnemius but received no treatments. Groups C, D, and E containing 16 CMPS rats in each group were the trial groups receiving heat-conduction dry needling therapy. In detail, rats in Group C received dry needling treatment at the heating temperature of 44°C. Rats in Group D received intramuscular injection of capsazepine before receiving dry needling treatment with the heating temperature at 44°C. Rats in Group E received dry needling treatment with the heating temperature at 40°C. The mRNA expression of TRPV1, protein kinase C (PKC), and interleukin (IL)-6 in the needle insertion points of musculus gastrocnemius was measured at 24 hrs and 7 days after dry needling therapy.
Results: Compared with untreated CMPS rats, the mRNA expression of TRPV1, PKC, and interleukin-6 (IL-6) was increased in rats receiving dry needling therapy with the heating temperature at 44°C for 24 hrs. However, the mRNA expression of TRPV1, PKC, and IL-6 in CMPS rats receiving injection of TRPV1 antagonist capsazepine into musculus gastrocnemius followed by temperature-needling at 44°C was analogous to that in untreated CMPS rats.
Conclusion: Dry needling therapy with needles heated to 44°C could impact the activity of TRPV1/PKC/IL-6 pathway.
Keywords: dry needling, myofascial pain syndrome, transient receptor potential, heat, capsazepine