INIMEC - CONICET   05467
INSTITUTO DE INVESTIGACION MEDICA MERCEDES Y MARTIN FERREYRA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
NO SEX DIFFERENCES IN GABAA RECEPTOR FUNCTION AND SUBUNIT EXPRESSION IN HYPOTHALAMIC NEURONS OF RAT EMBRYOS
Autor/es:
MIR, F.; CAMBIASSO, M.J.; CARRER, H.F.; AGUAYO, L.G.
Lugar:
Dourado
Reunión:
Simposio; First Brazilian International Symposium on Integrative Neuroendocrinology; 2011
Resumen:
"NO SEX DIFFERENCES IN GABAA RECEPTOR FUNCTION AND SUBUNIT EXPRESSION IN HYPOTHALAMIC NEURONS OF RAT EMBRYOS " Mir F.R.1, Cambiasso M.J.1, Carrer H.F.1 and Aguayo L.G.2 1Laboratorio de Neurofisiología, Instituto de Investigación Médica Mercedes y Martín Ferreyra. Argentina 2Laboratorio de Neurofisiología, Departamento de Fisiología, Universidad de Concepción. Chile GABAA receptors (GABAAR) are members of the ligand-gated ion channel family. They are composed of five subunits arranged around a central pore that allows the influx of chloride ions. Presently, 20 different subunits have been identified and the most prevalent conformation of the receptor is α1β2γ2. Pharmacological and electrophysiological properties of GABAAR, such as sensitivity to GABA and modulators as well as the duration and number of open states, are dependent on subunit conformation. In addition, the activity of GABAAR can be modulated by a variety of pharmacologically and clinically important drugs such as benzodiazepines, barbiturates, steroids, ethanol and general anesthetics. It is extensively accepted that sex hormones secreted by embryonic testes are the main responsible to determine sexual differentiation of the brain in a developmental narrow time window (E18-PN10). Previous results from our laboratory revealed that the area, amplitude and duration of the response to 10 µM muscimol are greater in male than female hypothalamic neurons of E16 rat embryos. These differences arise before neurons underwent sex steroids mediated sexual differentiation. Objective: To search for sex differences in GABAAR function and subunit expression of hypothalamic neurons from rat embryos before critical period of sexual differentiation. Methods and results: To reach our objective, we conducted a pharmacological characterization of GABAAR in hypothalamic neurons of male and female E16 embryos. The cells were grown for 2 or 9 DIV and used for whole-cell patch clamp recordings. Responses to different GABA concentrations were recorded to obtain a concentration-response curve for males and females. The percentage of potentiation or inhibition of 10 µM GABA-elicited currents in the presence of allosteric modulators such as diazepam (1 µM), alfaxalone (50 µM), propofol (5 µM), Zn+2 (1 µM), furosemide (500 µM), muscimol (10 µM), TIHP (1 µM), Ro 15-4513 (0.3 µM), La+3 (100 µM) and ethanol (1, 10, 50, 100 and 200 mM) were analyzed. There were no statistical differences between male and female sensitivity to GABA as evaluated by means of EC50 comparison. The percentages of potentiation and inhibition of a variety of allosteric modulators showed no sex difference. To elucidate if there are sex differences in expression of GABAAR subunits, mRNA from 2 DIV sexually discriminated cultures was extracted. RT-PCR was performed in order to amplify GABAA receptor subunits (α1-6, β1-3, γ1-3, δ) and β-actin samples. As we expected from analysis of physiological data, the expression pattern of GABAAR subunits showed that most subunits were present in cultured neurons from both sexes. Conclusion: Our data confirm at both the functional and expression levels, that GABAAR subunits in hypothalamic neurons from E16 embryos are not different in males and females before the hormonal mediated sexual differentiation. Financial support: ANPCyT PICT26331 and 0456, CONICET PIP2010, MinCyT CBA PID2008 and NIH RO1 15015.