Characterization and functions of GABAérgic system in adult rat pineal gland

BENITEZ, SERGIO; FARIAS ALTAMIRANO, LUZ; PENISSI, ALICIA; MUÑOZ, ESTELA

Mar del Plata

Congreso; XXX Congreso Anual SAN 2015; 2015

Sociedad Argentina de Investigación en Neurociencias

Circadian modulation of organismal physiology and behavior facilitates adaptation to environmental changes. One of the principal regulators of the mammalian circadian timing system is the pineal gland, which is the main source of circulating melatonin, a major endocrine effector of the system. We analyzed the influences of the GABAergic system in physiology of the adult rat pineal gland. The GABAergic innervation showed a marked tropism for blood vessels. Moreover, a subpopulation of interstitial cells (approximately 5% of total cells in the gland) immune-positive for cytoplasmic vimentin, GAD65, GAD67 and GABA was clearly identifiable. The spatial and temporal distribution of the α1 subunit of the ionotropic GABAA receptor and the B1 subtype of the metabotropic GABAB receptor, implicates GABA in the presynaptic modulation of GABAergic and sympathetic nerve fibers, in vascular tone regulation, and in the maintenance of the quiescent status of potential Pax6+ precursors in the adult PG. In vivo and in vitro pharmacological manipulations of GABAA receptors altered pineal serotonin levels, suggesting an inhibitory effect of GABA on the synthesis and secretion of NA-induced melatonin. 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.