Cellular and functional characterization of the GABAergic system in the adult rat pineal gland

L.E. FARIAS ALTAMIRANO; S.G. BENITEZ; A.B. PENISSI; E.M. MUÑOZ

Mar del Plata

Congreso; SAN2015; 2015

Sociedad Argentina de Investigación en Neurociencias-SAN

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 (PG), which is the main source of circulating melatonin. The indole rhythm is under sympathetic regulation via local norepinephrine (NE) release at night from the nerve ends of neurons located in the superior cervical ganglia (SCG). In this work we studied the influences of the GABAergic system in the physiology of the adult rat PG. The GABAergic innervation showed a marked tropism for blood vessels. Moreover, a subpopulation of interstitial cells immunoreactive 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 NE-induced melatonin. Our results, together with previous bibliographic data, allow us to propose a hypothetical model of melatonin rhythm modulation by the local GABAergic system in the adult rat pineal gland.