Topical analgesics and blood pressure during static contraction in humans.
OBJECTIVE
In decerebrate cats, topical application of analgesic balm (AB) can attenuate the pressor response to electrically induced static contraction. We examined the possibility that this phenomenon also occurs in humans and determined whether such effects were limited to a local action on the contracting muscle (e.g., attenuations of the action of groups III and IV muscle afferents that cause the exercise pressor reflex) or whether they also may have affected active muscle blood flow and/or central command.


METHODS
Blood pressure (mean arterial pressure (MAP)), heart rate (HR), brachial artery blood flow (BABF), and relative perceived exertion (RPE) were assessed at rest and during 90 s of static handgrip contraction before and 50 min after application of a commercially available AB (1% capsaicin, 12.5% methyl salicylate) to the skin of the forearm muscles.


RESULTS
AB attenuated the MAP response to contraction (19 +/- 3 vs 27 +/- 5 mm Hg) but had no effect on the HR response. Absolute BABF was enhanced at rest and during contraction, but absolute (118 +/- 47 vs 114 +/- 47 mL x min) and percent increases (83 +/- 31 vs 55 +/-19%) were not statistically different between conditions. AB appeared to slightly enhance RPE, but this was also the case in a control protocol where only the vehicle (petroleum jelly) was used and no change in the blood pressure response was seen.


CONCLUSIONS
AB attenuates contraction-induced increases in MAP that do not seem to be related to alterations in perfusion of active muscle or central command. Effects appear to be localized to the active skeletal muscle and likely involve reductions in sensitivity of groups III and IV muscle afferents to local chemical and/or mechanical stimulation.
Dawson
Alison N
AN
University of California, Davis, Departments of Internal Medicine, Division of Cardiovascular Medicine, and Human Physiology, Davis, CA 95616, USA.
Walser
Buddy
B
Jafarzadeh
Mehrdad
M
Stebbins
Charles L
CL
D000287:Administration, Topical; D000328:Adult; D000700:Analgesics / Q000008:administration & dosage / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D002140:California; D002211:Capsaicin / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D005542:Forearm / Q000098:blood supply / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology; D005082:Physical Exertion / Q000187:drug effects / Q000502:physiology*; D012039:Regional Blood Flow / Q000187:drug effects; D012459:Salicylates / Q000008:administration & dosage / Q000494:pharmacology
D000700:Analgesics; D012459:Salicylates; C033069:methyl salicylate; D002211:Capsaicin