Transient expression of vanilloid receptor subtype 1 in rat cardiomyocytesduring development

Vanilloid receptor subtype 1 (VR1) is a nonselective cation channel detecte d on sensory neurons that is sensitive to capsaicin, the main pungent ingre dient of hot chilli pepper. Capsaicin application to neonatal animals cause s cardiorespiratory distress, and this susceptibility to capsaicin changes during early postnatal life. This prompted us to hypothesise that in additi on to its known neuronal localisation, VR1 is also expressed by non-neurona l cells of the heart during development. This issue was addressed in the ra t heart during pre- and postnatal development by means of RT-PCR, western b lot and immunohistochemistry. VR1-mRNA was transiently expressed from E14 t o P30 but absent from adult hearts. Translation into protein was verified b y western blotting. Immunohistochemistry proved that VR1 protein was locali sed in cardiomyocytes during those developmental stages at which mRNA was d etected. In conclusion, VR1 is not neuron-specific but is transiently expre ssed on cardiomyocytes during ontogeny thereby pointing to a developmental role of this cation channel.