TRPA1 are cation channels expressed in sensory neurons and in several other cell
types. This channel is specifically activated by ally isothiocyanate (AITC), the pungent
component of mustard oil, as well as by other electrophilic compounds. Although
TRPA1 expression in central glia has been reported, its subcellular localization
and its expression in peripheral glia have not been investigated before. In this
paper we report the molecular and functional expression of TRPA1 in rat cortical astrocytes.
Real-time RT-PCR identified low but significant amounts of TRPA1 mRNA
in cortical astrocytes while no signal was seen in peripheral glia isolated from dorsal
root ganglia (DRG) or in a glial cell line (DITNC-1). Calcium imaging showed
AITC-induced signals in astrocytes while no response in peripheral glia. AITC induced
calcium signals in astrocytes in the presence and in the absence of extracellular
calcium, suggesting an intracellular localization of TRPA1 channels. Whole cell electrophysiological
recordings were performed in astrocytes, in peripheral glia and in
DITNC-1 cells transfected with TRPA1 during AITC application. In TRPA1-transfected
DITNC-1 cells typical TRPA1 currents were recorded with a reversal potential
near 0 mV, consistent with the opening of a non-selective cation channel. No such
currents were recorded in untransfected DITNC-1 cells, in astrocytes and in peripheral
glial cells, where even high concentrations of AITC (up to 10 mM) induced no
significant outward current. In astrocytes AITC transiently induced an outward rectifying
current with the reversal potential near 1290 mV, consistent with K channel
activation, likely activated by intracellular release of calcium. Our results suggest that
TRPA1 channels are molecularly and functionally expressed in calcium-containing
organelles of rat cortical astrocytes, with no expression in the plasma membrane