Endothelin-3 applied to the brain evokes opposite effects on bile secretion mediated by a central nitric oxide pathway

We sought to establish Endothelin (ET-3) role in the central regulation of bile secretion in the rat. The intracerebroventricular (icv) injection of ET-3 evoked a cholestatic or a choleretic effect depending on the administered dose. Lower doses increased bile flow and bicarbonate excretion, whereas higher doses decreased bile flow and bile acid output. ET-3 effects were dependent on brain nitric oxide and independent of the autonomic nervous system or hemodynamic variations. A selective ET_B antagonist abolished the cholestatic effect, whereas the choleretic effect was totally inhibited by either ET _A or ET_B selective blockade. These results show that ET-3 applied to the brain modified through a nitric oxide pathway distinct bile flow fractions depending on the administered dose and give further insights into the complexity of brain-liver interaction.