2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
SENSITIVITY TO COLD IN HUMAN.
DIFFERENT RESPONSES TO MENTHOL ARE ASSOCIATED WITH
DIFFERENT RESPONSES TO COLD
Tamara V. Kozyreva*, Elena Ya. Tkachenko
Institute of Physiology, Russian Academy of Medical Sciences, Novosibirsk, Russia
Contact person: Kozyreva@iph.ma.nsc.ru
INTRODUCTION
Thermal sensation is the composite of the function of thermoreceptors that provide the
perception of a thermal signal, its transduction in the nervous system code, signal
transmission to the central nervous system structures, its analysis and synthesis by specific
cortical areas ending up with sensation formation. The relations between heat exchange and
thermoregulation as a whole are reflected in thermal sensation.
It is known that the analyzer systems are capable of changing their action by altering the
impulse activity of the receptors and/or the number of functioning receptors depending on the
environmental conditions and the organism functional state. Thus, the number of functioning
cold receptors changes at decreased skin temperature and during long-term adaptation to cold,
heat and physical training (1).
In recent years, numerous studies have been concerned with the molecular mechanisms of
thermal sensitivity. It is believed that the thermosensitive TRP ion channels act as detector of
changes in temperature and as the main sensors in the peripheral nervous system (2, 3). It has
been demonstrated that TRPM8 (a member of the TRP channel family) is an ion channel
activated by cold and menthol (2, 3, 4, 5). There are also data indicating that menthol
increases the susceptibility of the cold sensitive peripheral vasoactive C nociceptors and
activates the cold specific A delta fibers (6). The involvement of the menthol sensitive
thermoreceptors in the formation of a conscience thermal sensation in human has been poorly
studied.
METHODS
50 healthy volunteers, men and women, aged 24.3±1.15 years were studied. Their heightweight
coefficient was 2.8±0.06. They were informed about the aim of the study and the
procedures performed in compliance with the Declaration of Helsinki. The volunteer dressed
in light clothes was placed in a thermostatic chamber at 23°C seating on the armchair. During
the study, skin temperature and cold sensitivity were measured initially and after local
cooling. All measurements were repeated after menthol application.
Estimation of cold sensitivity was based on counts of the number of cold spots (this was an
estimate of the number of functioning cold receptors) in a 100-spot matrix (an area of 25 cm 2 )
in the internal surface of the forearm. The diameter of the thermode tip was 1 mm, its
temperature was 3-4°C.
Forearm cooling in the matrix area was made during 5 minutes with an thermode of 25 cm 2 ,
its temperature was 8-10°C.
A 1% menthol solution (Menthol, Sigma) in 50% ethyl alcohol was applied for 5 min at the
matrix site of right forearm. Judging by the literary data, the solvent ethanol itself has no
effect on thermal sensitivity in used time periods for testing thermal sensitivity after menthol
application (6, 7).
Experimental design. At the initial state, temperature and the number of cold spots were
measured in the internal surface of both forearms. The effect of menthol on the cold receptor
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