Effects of a menthol-based analgesic balm on pressor responses evoked from muscle afferents in cats.
OBJECTIVE
To evaluate changes in heart rate (HR) and mean arterial pressure (MAP) as indicators of changes in pressor response for muscle afferents after topical application of menthol (MEN)-based analgesic balm.


METHODS
11 decerebrate cats.


METHODS
Pressor responses were reflexively evoked by static contraction of hind limb muscles, which are caused by group III and IV afferents. Responses were monitored without interference from anesthesia or effects of higher brain function by the use of decerebrate cats. After obtaining baseline data, MEN analgesic balm (1.9%) was applied to the skin over contracting muscles of 1 hind limb in 6 cats; petrolatum was applied to 5 control cats. Muscle contractions were evoked every 10 minutes, alternating between hind limbs, for 120 minutes. Peak MAP and HR were analyzed.


RESULTS
Peak MAP responses evoked by static muscle contraction for the ipsilateral hind limb were significantly attenuated 20 minutes after application, but approached baseline values 40 minutes after application. The pressor response was significantly decreased 20 minutes after application during the last 12 seconds of the stimulus, which was attributed to group IV afferents. There were no significant differences in HR responses.


CONCLUSIONS
Application of MEN analgesic balm to the skin over contracting muscles significantly decreased the pressor response to static muscle contractions. This suggests that topical application of MEN has effects on responses evoked from receptors located in muscles. The MEN analgesic balm appeared to attenuate the pressor response 20 minutes after application, but it was a short-term effect.
Department of Veterinary Biosciences, College of Veterinary Medicine, University of Illinois, Urbana, IL 61801, USA.
Brian G
BG
Ragan
Amanda J
AJ
Nelson
Jonathan H
JH
Foreman
Gerald W
GW
Bell
Gary A
GA
Iwamoto
D000287:Administration, Topical; D000700:Analgesics / Q000008:administration & dosage / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D004558:Electric Stimulation; D006339:Heart Rate / Q000187:drug effects; D008610:Menthol / Q000008:administration & dosage / Q000494:pharmacology*; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation*; D009475:Neurons, Afferent / Q000187:drug effects*; D011311:Pressoreceptors / Q000187:drug effects*; D013997:Time Factors
D000700:Analgesics; D008610:Menthol