Abstract
In TRP (Transient Receptor Potential) cation channels family, cooling activated channels, TRPM8 and TRPA1, were identified in peripheral sensory neurons. However, it is still controversial whether TRPA1 is activated by cooling. Story et al [Cell,2003] reported that TRPA1 is activated by cooling below 17oC. In contrast, Jordt et al [Nature,2004] reported that cooling did not activate TRPA1. Here, we investigated thermal sensitivity of TRPA1 by Fura-2 microfulorimetry and patch-clamp recordings in TRPA1-expressing HEK293 cells. 1: Cooling increased intracellular calcium levels. 2: In whole-cell voltage-clamp recording (-60mV), cooling below threshold evoked inward current. Threshold temperature was 17.5 ± 2.7 oC. 3: In inside-out single-channel recording, cooling induced activities of ion channels with non-selective cation channel properties. This indicated that channel activities occurred without intracellular soluble component. Single channel currents showed inward rectification. Single channel conductance was 74.1 ±18.8pS We conclude that TRPA1 is non-selective cation channel, activated by cooling. [J Physiol Sci. 2006;56 Suppl:S153]
