Salicylate-based analgesic balm attenuates pressor responses from skeletal muscle

Analgesic balms (AB) are widely used in sports medicine. We previously have examined effects of various counterirritant-based AB on pressor responses evoked by muscular contraction (MC), mediated by group III and IV muscle afferents known to produce exercise and nociceptive responses. Our purpose was to examine trolamine salicylate-based analgesic balm (TS) effects.

Ten healthy, adult male and female cats were used. Decerebration under halothane allowed elimination of anesthesia. Electrical stimulation of L7 and S1 ventral roots evoked static MC (30 s). After control runs, commercial TS (10% concentration) was applied to the skin over the contracting muscles of one hind limb (N = 5). MC was evoked every 10 min, alternating between sides. Ipsilateral (T = 0, T + 20, T + 40, T + 60 min) and contralateral (T - 10, T + 10, T + 30, T + 50 min) responses were analyzed. Five additional cats received AB minus TS.

There were significant attenuations in both peak mean arterial pressure (MAP), in the last 12 s and the last 6 s of the 30 s of MC for both contra- and ipsilateral limbs occurring at T + 50 and T + 60 min after TS application, respectively. No significant changes in heart rate (HR) responses were seen for either the ipsi- or contralateral stimulation. There were no changes in MAP or HR in control cats.

These results indicate that TS affects the end of the 30 s of MC, which is thought to be mainly chemically mediated through group IV afferents. TS represents the salicylate class of AB and has no counterirritant properties. TS works as an inhibitor of cyclooxygenase (prostaglandin formation) and is, at least in part, blood borne.