Effect of Skin Ion Channel TRPM8 Activation by Cold and Menthol on Thermoregulation and the Expression of Genes of Thermosensitive TRP Ion Channels in the Hypothalamus of Hypertensive Rats

ISIAH (inherited stress-induced arterial hypertension) rats are characterized by high blood pressure and decreased Trpm8 gene expression in the anterior hypothalamus. Thermosensitive ion channel TRPM8 plays a critical role in the transduction of moderately cold stimuli that give rise to cool sensations. In normotensive animals, the activation of skin TRPM8 is known to induce changes in gene expression in the hypothalamus and induce alterations of thermoregulatory responses. In this work, in hypertensive rats, we studied the effects of activation of the peripheral TRPM8 by cooling and by application of a 1% menthol suspension on (1) the maintenance of body temperature balance and (2) mRNA expression of thermosensitive TRP ion channels in the hypothalamus. In these hypertensive animals, (1) pharmacological activation of peripheral TRPM8 did not affect the thermoregulatory parameters either under thermoneutral conditions or during cold exposure; (2) the expression of Trpm8 in the anterior hypothalamus approximately doubled (to the level of normotensive animals) under the influence of (a) slow cooling and (b) at pharmacological activation of the peripheral TRPM8 ion channel. The latter fact seems the quite important because it allows the proposal of a tool for correcting at least some parameters that distinguish a hypertensive state from the normotensive one.