Cutaneous blood flow and sweat rate responses to exogenous administration of acetylcholine and methacholine

Kenichi Kimura, David A. Low, David M. Keller, Scott L. Davis, Craig G. Crandall

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

The aim of this study was to evaluate cutaneous vasodilation and sweating responses to exogenous administration of acetylcholine (ACh) and methacholine (MCh), which have different sensitivities to endogenous cholinesterase. Four intradermal microdialysis probes were placed in dorsal forearm skin: two sites were perfused with ACh (1 × 10-7-1 M) and the other two with the same molar concentrations of MCh. Sweat rate (SR) and cutaneous blood flow were simultaneously assessed directly over each microdialysis membrane. Dose-response curves were constructed, and the effective concentration of the drug resulting in 50% of the maximal response (EC50) was identified. For SR and cutaneous vascular conductance (CVC), there were no significant differences in EC50 between sites receiving the same drug: -1.52 ± 0.18 and -1.19 ± 0.09 log-molar concentration of ACh at distal and proximal sites, respectively, and -2.35 ± 0.24 and -2.42 ± 0.23 log-molar concentration of MCh at distal and proximal sites, respectively, for SR (P > 0.05) and -3.87 ± 0.32 and -3.97 ± 0.27 log-molar concentration of ACh at distal and proximal sites, respectively, and -4.78 ± 0.17 and -4.46 ± 0.16 log-molar concentration of MCh at distal and proximal sites, respectively, for CVC (P > 0.05). However, the EC 50 for CVC and SR was significantly lower at the MCh than at the ACh sites. A second procedure was performed to confirm that differences in responses between ACh and MCh could be attributed to different cholinesterase sensitivities. Similarly, four microdialysis membranes were placed in dorsal forearm skin: two sites were perfused with ACh and other two with MCh. However, one of each of the ACh and MCh sites was also perfused with 10 μM neostigmine (an acetylcholinesterase inhibitor). Neostigmine at the ACh site induced a leftward shift (i.e., lower EC50) of the SR and CVC dose-response curves compared with the site treated with ACh alone, resulting in no difference in the EC50 for SR and CVC between the ACh +- neostigmine and the MCh site. These results suggest that elevations in SR and CVC occur earlier with MCh than with ACh treatment because of differences in cholinesterase susceptibility between these drugs.

Original languageEnglish (US)
Pages (from-to)1856-1861
Number of pages6
JournalJournal of Applied Physiology
Volume102
Issue number5
DOIs
StatePublished - May 2007

Fingerprint

Methacholine Chloride
Sweat
Acetylcholine
Skin
Blood Vessels
Neostigmine
Cholinesterases
Microdialysis
Forearm
Pharmaceutical Preparations
Sweating
Membranes
Cholinesterase Inhibitors
Vasodilation

Keywords

  • Microdialysis
  • Sweating
  • Thermoregulation

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

Cite this

Cutaneous blood flow and sweat rate responses to exogenous administration of acetylcholine and methacholine. / Kimura, Kenichi; Low, David A.; Keller, David M.; Davis, Scott L.; Crandall, Craig G.

In: Journal of Applied Physiology, Vol. 102, No. 5, 05.2007, p. 1856-1861.

Research output: Contribution to journalArticle

Kimura, Kenichi ; Low, David A. ; Keller, David M. ; Davis, Scott L. ; Crandall, Craig G. / Cutaneous blood flow and sweat rate responses to exogenous administration of acetylcholine and methacholine. In: Journal of Applied Physiology. 2007 ; Vol. 102, No. 5. pp. 1856-1861.
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