Characterization of GABAergic and glutamatergic cells in the rat pineal gland: A hypothetical model of melatonin rhythm modulation by GABA and glutamate.

BENITEZ SG; CASTRO A; PLANO SA; MUÑOZ EM

Mendoza

Congreso; XII Latin American Symposium on Chronobiology; 2013

In mammals, nocturnal pineal melatonin synthesis is controlled by the hypothalamic SCN through NE release from sympathetic fibers originating in the SCG. This regulatory pathway has been firmly established; nevertheless other less- characterized modulatory mechanisms have also been proposed. In this study, we analyzed the cellular location of certain components of the GABAergic and glutamatergic systems via IHC and ISH. In adult rat pineal gland, GABA, its biosynthetic enzymes GAD65 and GAD67, and subunits of the metabotropic GABAB receptor, GABABR1 and GABABR2, were observed in interstitial cells. GAD67 and GABA co-localized in these cells, supporting their GABAergic capability. GABA was immunodetected in both a sub-population of vimentin-positive astrocyte-like cells and Iba1-positive microglial cells. Furthermore, GABA and GABABR1 were observed in cells associated with blood vessels. GABABR1 was present in actin-enriched interstitial cells that resemble contractile pericytes. With regards to glutamatergic markers, most of the pinealocytes expressed Vglut1, and some of them exhibited the metabotropic receptor mGluR5 in their membranes. Our results, together with previous bibliographic data, allow us to propose a hypothetical model of melatonin rhythm modulation by the local GABAergic and glutamatergic systems in the rat pineal gland.