HRH3 and cholangiocarcinoma: Specifically, H3R stimulation by RAMH (acting via Gαi) inhibited hyperplastic biliary growth by inhibition of cAMP [34], while RAMH (acting through Gαo) decreased the growth of cholangiocarcinoma Mz-ChA-1 cells by inositol triphosphate (IP3)/Ca2+, which is independent of cAMP activation [32].