Arterial baroreceptors contain mechanosensors that detect the change in blood pressure, and transduce the mechanical signal into electrical signal transmitted via sensory neurons. The molecular identities of the baroreceptor mechanosensor are not fully understood, however, mechanosensitive ion channels are ideal candidates due to their ability to alter membrane potential. By mechanically stimulating the aortic baroreceptor neurons isolated from rat, we recorded a cation channel current comprising TRPC5. The baroreceptor TRPC5-containing channels were directly activated by membrane stretch on the soma and the neurite terminal. The channel activity was potentiated by Gd3+, but was abrogated by an anti-TRPC5 blocking antibody T5E3 and by expressing a dominant-negative TRPC5 construct T5DN. Calcium imaging and single-channel electrophysiology confirmed the mechanosensitivity of heterologously expressed mouse TRPC5 in cell lines. Disruption of TRPC5 function in rat baroreceptor neurons by lenti-virus mediated delivery of T5DN cDNA impaired the high blood pressure-induced firing frequency increase of the aortic depressor nerve, and it also impaired the baroreceptor-mediated reflex control of heart rate. In TRPC5 knockout (trpc5-/-) mice, the pressure-induced firing frequency increase was markedly attenuated, and the baroreflex responses were also impaired. TRPC5 thus forms a stretch-activated channel participating in the mechanotransduction at the aortic baroreceptor.