GHSR1a-constitutive activity inhibits presynaptic voltage gated calcium channels in cultured hypothalamic neurons

LOPEZ SOTO JE; AGOSTI F; RODRÍGUEZ SS; CASTROGIOVANNI D; PERELLO M; RAINGO J

Huerta Grande

Congreso; XXVIII Congreso Anual de la Sociedad Argentina de Investigación en Neurociencia; 2013

Sociedad Argentina de Neurociencia

Within the hypothalamus, several peripheral signals have been shown to modulate neuronal activity, including the orexigenic hormone ghrelin. Ghrelin effects are mediated by Growth Hormone Secretagogue Receptor Type 1a (GHSR1a), the highest constitutively activated G-protein coupled receptors known. We have already demonstrated that GHSR1a-constitutive activity tonically inhibits presynaptic voltage gated calcium channels (VGCC), CaV2.1 and CaV2.2, in a heterologous system. Here, we aimed to determine if native levels of GHSR1a are enough to control basal CaV2.1 and CaV2.2 currents in hypothalamic neurons. We performed whole-cell patch-clamp recordings in embryonic hypothalamic neuronal cultures from GHSR-eGFP reporter mice. We found that eGFP(+) neurons (expressing GHSR) have 50 % less of total native VGCC current than eGFP(-) neurons (no expressing GHSR), whereas NaV currents were not different between groups. Also, the application of exogenous ghrelin inhibits 25 % of VGCC current only in GHSR-expressing neurons. Interestingly, we observed a specific reduction of ω-Agatoxin IVA and ω-Conotoxin GVIA (selective CaV2.1 and CaV2.2 blockers, respectively) sensitive CaV currents in GHSR-expressing neurons, while conotoxin/agatoxin insensitive CaV current remain unchanged. Our results demonstrated that GHSR1a constitutive and ghrelin-evoked activity specifically inhibit presynaptic VGCC in hypothalamic neurons