Circulating or cerebrospinal fluid ghrelin regulates different neuronal circuits within the dorsal vagal complex

MARÍA PAULA CORNEJO; AGUSTINA CABRAL; PABLO NICOLÁS DE FRANCESCO; GIMENA FERNÁNDEZ; SPRING VALDIVIA; GUADALUPE GARCÍA ROMERO; MIRTA REYNALDO; MARIO PERELLÓ

Congreso; Sociedad Argentina de Neurociencias. XXIX Annual Meeting.; 2014

The dorsal vagal complex (DVC) of the brainstem includes the nucleus of the solitary tract (NTS), the area postrema (AP) and the dorsal motor nucleus of the vagus. The DVC is an integrative center that regulates food intake and relays autonomic neural circuits. The ghrelin receptor, also known as growth hormone secretagogue receptor (GHSR), is expressed in the DVC. Here, we performed an anatomical characterization of the distribution of GHSR in the DVC using a transgenic mouse in which the green fluorescent protein is controlled by the GHSR promoter. Also, we used double staining with markers of neuronal populations to characterize the GHSR-expressing neurons, and we used the marker of cellular activation c-Fos to study the responsiveness of GHSR-expressing neurons to ghrelin. We confirmed that GHSR-expressing neurons exist in all three components of the DVC. These GHSR-expressing neurons failed to express corticotrophin releasing factor, thyrotropin releasing hormone, neuropeptide Y, choline acetyl-transferase, tyrosine hydroxylase or Met-enkephalin. Interestingly, peripherally administered ghrelin mainly activates GHSR-expressing neurons of the AP, while centrally administered ghrelin activates GHSR-expressing neurons of both the AP and the NTS. Thus, GHSR-expressing neurons of the AP seem to sense plasma ghrelin, while GHSR-expressing neurons of the NTS mainly respond to cerebrospinal fluid ghrelin. The phenotype of these GHSR-expressing neurons remains to be determined.