Trip through the Pharmacology of hot- and cold sensing TRP Ion Channels

The warmth of the kiss of a beloved and the chilliness of cold winter winds are well known phenomenon liked or alternatively disliked by humans. Both are nothing but temperature sensations at two different levels. Mammals sense ambient temperature through primary afferent sensory neurons of the dorsal root ganglion and trigeminal ganglion. These cells convey thermal information from peripheral tissues to the spinal cord and brain where the signals are interpreted. This results in appropriate cognitive and reflexive responses. The mammalian nervous system is capable of performing its sensory function because of the presence of thermo-TRPs at the peripheral free nerve endings and in keratinocytes. Thermo-TRPs is a subgroup of the TRP-super family of cation channels and consists of six members of diverse channel forming proteins. They are grouped together because one of their functions is thermal sensation. These are TRPM8 TRPV1-V4 and TRPA1. TRPA1 senses cold temperature below 15 ��C TRPM8 senses cool temperatures (< 25 ��C) TRPV3 and TRPV4 sense normal body warmth (28 ��C & 33 ��C ) TRPV1 senses hot temperatures (>42 ��C) and TRPV2 is involved in noxious heat sensation (>52 ��C).