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

URIARTE, MAIA; FERNÁNDEZ, GIMENA; DE FRANCESCO, PABLO N.; LUFRANO, DANIELA

Congreso; 2nd Federation of Latin American and Caribbean Neuroscience Societies Congress; 2016

Ghrelin is a peptide hormone secreted from the stomach that mainly acts in the central nervous system. However, the accessibility of plasma ghrelin to the brain is limited and restricted to few specific brain areas. The goal of this study was to get insights into the system mediating the transport of ghrelin from the plasma to the brain in mice. First, we centrally infused a fluorescent ghrelin analog to mice and look for brain cells labeled by the tracer. We found that both the ependymal cells of the choroids plexus and the hypothalamic tanycytes display tracer labeling.Then, we peripherally infused the fluorescent ghrelin analog to mice and look for brain cells labeled at different time points. We found that the hypothalamic tanycytes were early labeled by the probe, and that the periventricular brain parenchyma was also labeled after 15 min of treatment. In order to test if the accessibility of ghrelin to the brain depends on a saturable mechanism, we centrally infused mice with a scrambled fluorescent ghrelin peptide and then peripherally injected ghrelin. We found that the centrally-administered scrambled peptide labeled tanycytes and failed to affect food intake; however, it impaired the orexigenic activity as well as the increase of the marker of cellular activation c-Fos induced by peripherally administered ghrelin. Thus, we conclude that hypothalamic tanycytes may be involved in the transport of ghrelin in a blood-to-brain direction.Supported by PICTO 2013-0065.