Author: Wollweber BT, University of Marburg, Department of Physiology.
Names and affiliation of other authors:
andolf A, Schäfer MKH, Wegner S, Postnova S, Voigt K, Braun HA
Oral or poster: Oral presentation
The hypothalamus plays an important role in temperature regulation while menthol is a chemical analogue of cooling which enhances peripheral temperature sensitivity. We have examined neuromodulatory menthol effects in hypothalamic neurons to evaluate the underlying ionic mechanisms which, in peripheral neurons, are attributed to the activation of TRPM8 channels.
Different techniques are used. Extracellular recordings from hypothalamic neurons demonstrated that menthol also modulates neuronal activity in the brain: it reduces the firing rate of warm-sensitive neurons. Additionally, with RT-PCR and in situ hybridization (ISH) we could demonstrate that TRPM8 is also expressed in the hypothalamus.
However, peripheral menthol effects are not attributed to an inhibition of warm sensitive but to an activation of cold sensitive neurons. Moreover, activation of TRPM8 channels should lead to depolarization with increasing firing rate. Hence, the mechanisms seem to be different. This is also indicated by recent patch-clamp experiments on hypothalamic GT1-7 neurons where we found a reduction of an outward current during menthol application. These neurons, as we could show, do not express TRPM8. Therefore TRPM8 probably plays no role in the modulations of central temperature sensitivity. Other mechanisms have to be considered which currently are examined with further patch-clamp experiments in combination with a Hodgkin-Huxley type model on the basis of the experimental data.