Angiotensin II change glutamate uptake and GFAP expression in astrocyte culture from hypothalamus

Abstract

Central ANG‐II induce vasopressin and oxytocin release (Reis et al. Behav Brain Funct. 2010). Considering that dehydration diminishes glutamate uptake by hypothalamic astrocyte, as well induce retraction of astroglial processes (Boudaba et al. J Physiol 2003). We hypothesized that ANG II could modulate magnocellular excitability through a decrease of glutamate uptake and/or change in glial fibrillary acidic protein (GFAP) expression in hypothalamic astrocytes. We aimed to study the role of ANG II modulating glutamate uptake and GFAP expression in hypothalamic astrocytes cultured. Astrocyte culture were stimulated with ANG‐II (1, 10 and 100 nM) during 5, 15 and 30 min. Glutamate uptake was evaluated through [3H] aspartate assay and GFAP expression was evaluated after ANG‐II (100 nM) stimulus during 5, 15 and 30 min through Western Blot Analysis [protein membrane were incubated with mouse α‐GFAP (1:500) or β‐galactosidase (1:3000)]. The results showed that ANG‐II time‐and concentration‐ dependent induced a significant decrease in aspartate uptake. Maximal decrease was observed at 5 min with 100 nM Ang II [47±5.2% under control (n= 11)]. ANG‐II induced a time‐dependent increase in the GFAP expression, with maximal increase at 15 min [57±24% above control (n=06)]. The results suggest that the diminished glutamate uptake induce by ANG‐II increases the availability of extracellular glutamate within the hypothalamus, which could contribute to an increased magnocellular neuronal excitability. In addition, GFAP expression induced by ANG‐II could act modulating availability of extracellular glutamate. Financial Support: FAPESP, CNPq.