To explore the effects of 1% lidocaine on pain threshold in rats with myofascial pain syndrome (MPS) based on cyclic adenosine monophosphate (cAMP) / protein kinase A (PKA)/peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) signaling pathways.

The models of MPS rats were prepared by striking manipulation + fatigue method, and they were randomly divided into model group, combined group, experimental-L group and experimental-H group, 10 rats in each group. Another 10 rats were selected as blank group. After successful molding, experimental-L group and experimental-H group were given injection of 1% lidocaine (0.25 mL, 0.5 mL) at pain trigger site of right medial thigh (once a week), combined group was given intraperitoneal injection of SR-18292 (30 mg·kg^-1, 3 times a week) on basis of experimental-H group, model group and blank group were given injection of normal saline (once a week) at pain trigger site of right medial thigh or at the same site. Five groups were treated for 3 weeks. The pain threshold was detected by mechanical stimulation and thermal stimulation, level of adenosine triphosphate (ATP) in muscle tissues at pain trigger site was detected by the kit, and expressions of cAMP, PKA and PGC-1α proteins were detected by Western blot.

After 3 weeks of intervention, paw withdrawal mechanical threshold (PWMT) values in experimental-H group, combined group, model group and blank group were (51.69±7.22), (37.84±6.29), (20.33±5.83) and (67.88±8.46) g, paw withdrawal latency (PWL) values were (10.58±1.03), (7.89±0.87), (6.33±0.92) and (12.89±1.64) s, ATP levels were (866.37±98.66), (728.81±89.60), (617.52±89.84) and (1 098.45±101.36) μmol·g^-1, relative expression levels of cAMP protein were 0.53±0.08, 0.48±0.07, 0.21±0.06 and 0.68±0.10, relative expression levels of PKA protein were 0.60±0.06, 0.58±0.08, 0.28±0.05 and 0.79±0.09, relative expression levels of PGC-1α protein were 0.78±0.05, 0.59±0.06, 0.41±0.08 and 0.93±0.09, and the differences were statistically significant between experimental-H group, combined group and mode group (all P<0.05).

1% lidocaine can improve pain threshold and mitochondrial energy metabolism in muscle tissues of affected limbs in MPS rats, which may be related to activating cAMP/PKA/PGC-1α signaling pathways.