2007, Piran, Slovenia

Cold physiology
number was estimated 5 and 30 min after menthol application in the right forearm. Test
cooling of the same intensity and duration was done before menthol application in the left
forearm, and after it in the right forearm. This allowed us to exclude repeated cold exposure
of the same skin region. The effect of cooling on the number of cold spots was estimated at
decreased temperature immediately after the thermode moving away. In 15 min after local
cooling the temperature and the number of cold spots returned to the level which had been
observed before cooling.
In special series of experiments the warm sensitivity before and after menthol application was
measured. The number of warm spots was estimated similarly to the number of cold spots but
at a thermode temperature of 41°C.
RESULTS AND DISCUSSION
Initially forearm skin temperature was 32.2±0.11ºС at the left and 32.3±0.09ºС at the right.
Menthol had no effect on the skin temperature. Under the test cooling the temperature was
decreased by 4.0±0.12ºС. Menthol and test cooling had no effect on the number of warm
spots in the forearm.
Analysis of cold sensitivity in the response to menthol application disclosed variant groups
due to individual sensitivity to menthol. The main group A (70% of the total number of
subjects) showed the following changes. In this group cooling of the forearm without menthol
was associated with a decrease in cold spots (CS) number by 34.7% (Table 1A). Five minutes
after menthol application, the number of CS in the area exposed to menthol significantly
decreased (by 45%); 30 min later the effect of menthol persisted in this group, and in some
subjects it kept increasing, i.e. the number of CS further decreased (Fig. 1A). Cooling 40 min
after menthol application caused a further decrease in the number of sensitive CS by another
43.9% (Table 1A).
In group B (14% of the total number of subjects), in contrast to the group A, CS number
increased by 40% 5 min after menthol application, and returned to the initial level after 30
min (Fig. 1B). Subjects of this group showed no significant change in CS number under test
cooling before menthol application and on the background of its effect (Table 1B). This may
be evidence of a weaker effect of cold on the number of functioning cold receptors in subjects
of this group.
Finally, in subjects of group C (16% of the total number), was associated with change in CS
number neither 5 min after nor 30 min after menthol application (Fig. 1C). It should be noted
that the initial CS number in group C was greater than in group A (51.4±8.45 versus
36.3±2.37; P