Potential role of hypothalamic tanycytes mediating the bood to brain transport of ghrelin

MAIA URIARTE; NICOLAS DE FRANCESCO; GIMENA FERNANDEZ; AGUSTINA CABRAL; GUADALUPE GARCÍA ROMERO; MIRTA REYNALDO; MARIO PERELLÓ; DANIELA LUFRANO

Congreso; 2nd FALAN Congress; 2016

Ghrelin is apeptide hormone secreted from the stomach that mainly acts in the centralnervous system. However, the accessibility of plasma ghrelin to the brain islimited and restricted to few specific brain areas. The goal of this study wasto get insights into the system mediating the transport of ghrelin from theplasma to the brain in mice. First, we centrally infused a fluorescent ghrelinanalog to mice and look for brain cells labeled by the tracer. We found thatboth the ependymal cells of the choroids plexus and the hypothalamic tanycytesdisplay tracer labeling.Then, we peripherally infused the fluorescent ghrelinanalog to mice and look for brain cells labeled at different time points. Wefound that the hypothalamic tanycytes were early labeled by the probe, and thatthe periventricular brain parenchyma was also labeled after 15 min oftreatment. In order to test if the accessibility of ghrelin to the braindepends on a saturable mechanism, we centrally infused mice with a scrambledfluorescent ghrelin peptide and then peripherally injected ghrelin. We foundthat the centrally-administered scrambled peptide labeled tanycytes and failedto affect food intake; however, it impaired the orexigenic activity as well asthe increase of the marker of cellular activation c-Fos induced by peripherallyadministered ghrelin. Thus, we conclude that hypothalamic tanycytes may beinvolved in the transport of ghrelin in a blood-to-brain direction.