LOCALIZATION OF ANGIOTENSIN II AT2 RECEPTORS IN THE INFERIOR COLLICULUS.

M.E ARCE- G.M. CIUFFO

Buzios, Brasil

Congreso; I CONGRESSO IBRO/LARC DE NEUROCIENCIAS DA AMÉRICA LATINA, CARIBE E; 2008

IBRO-LARC

Angiotensin II (Ang II) is not solely associated with fluid homeostasis and blood pressure control but it can also modulate neuronal activity in regions of the brain involved in cognition, motor control and sensory integration. Ang II recognizes two receptor subtypes, named as AT1 and AT2, based on pharmacological basis. AT2 receptors are highly expressed in neonatal tissues, with a rapid decrease after birth and persist in adulthood in limited brain areas. The Inferior Colliculus (IC) is a critical midbrain station for the auditory processing, involved with motor activities related to audition. The aim of this work was to study the localization of Ang II type 2 receptor in the IC during development. We studied the localization of Ang II receptors by binding autoradiography in pups at different stages after birth. Newborn animals (PND0) exhibited very low binding at the IC, which increase in PND8 and PND15 pups. Specific binding was stronger in PND15 animals with prevalence of AT2 receptors. Immunohistochemistry and immunofluorescence staining evidence the presence of neurons expressing AT2 receptors, confirming the observation by binding autoradiography. The expression of AT2 receptors was detected and semiquantified by multiplex RT-PCR. mRNA of AT2 receptors was co-amplified with GAPDH, allowing us to quantify messenger expression, which was higher in 15 day-old animals. The IC seems to be involved in the behavior related to sound input, such as patterns of hunting, escape or vocal communication. The pattern of Ang II at2 receptors expression in the Ic encompasses the pattern of the brainstem maturation and connection to the cerebral system. We assume that AT2 receptors might play a potential role in organogenesis and the establishment of neuronal circuits.