Effect of allopregnanolone on the GnRH secretion from the hypothalamus of pubertal female rats.

GIULIANI F.; DIGIORGO N.; YUNES R.; LACONI M.; LUX LANTOS V.; CABRERA R.

San Pablo- Brasil

Workshop; IWNE. International Workshop in Neuroendocrinology 2013; 2013

IWNE

Effect of allopregnanolone on the GnRH secretion from the hypothalamus of pubertal female ratsGiuliani Fernando A?*, Di Giorgio Noelia P§, Lux Lantos Victoria AR§, Cabrera Ricardo?.? INBIOMED- (Universidad de Mendoza) - IMBECU-CONICET. FCM (UN de Cuyo).§ Laboratorio de Neuroendocrinología - Instituto de Biología y Medicina Experimental (IByME)* fernando.giuliani@um.edu.arIntroduction: The early activation of the GnRH neural network at puberty is influenced by glutamatergic and GABAergic inputs whose activity may be regulated by factors such as the GABAA receptor modulator allopregnanolone (Allo). Previously we reported that the expression of the enzyme that synthesizes Allo increases in the hypothalamus as the rat develops from prepubertal to pubertal stage. Also, we demonstrated that Allo in vitro modulates the hypothalamic K+-evoked glutamate and GABA release through mechanisms mediated by GABAA and NMDA receptors and reduces the spontaneous release of GABA. We hypothesize that Allo is also able to regulate the pubertal GnRH release through the modulation of neurotransmitters receptors in a way that could correlate with our previous results.Objetives: (1) To determine the in vitro effect of Allo on the GnRH secretion from the hypothalamus of prepubertal (PP), vaginal opening (VO) and pubertal (P) rats; and (2) to determine the possible modulatory effect of Allo on GABAA and NMDA receptors.Methods: (1) Slices of mediobasal hypothalamus (MBH) and anterior preoptic areas (APOA) dissected from PP, VO and P rats were incubated for 30 min in 120 nM Allo after a 30 min pre-incubation with vehicle. (2) HMB-APOA slices from P rats were incubated for 30 min in 120 nM Allo supplemented with the GABAA receptor antagonist bicuculline (9.8 μM), the NMDA receptor antagonist AP-7 (100 μM) or the NMDA blocker Mg2+ (1.2 mM) after a 30 min pre-incubation with solutions of the antagonists alone. The supernatants of the experiments (1) and (2) were then used in a radioimmunoassay to measure the secreted GnRH. The results were compared by 2-way and 1-way ANOVA respectively and Bonferroni post tests (p<0.05 as significant).Results: (1) Allo induced a significant decrease in the hypothalamic GnRH secretion in slices of PP (p<0.01), VO (p<0.05) and P rats (p<0.05) regarding Veh groups. (2) In P rats the treatment with Bic, AP-7 and Mg2+ induced trends of reversion in the effect of Allo but such differences were not statistically significant (p>0.05).Conclusions: Allo reduces the GnRH secretion in the three ages studied. Although we can not rule out a mechanism dependent of modulation on NMDA or GABAA receptors, the effect of Allo on the GnRH release could be the result of the expected reduction in spontaneous GABA release that we have previously observed.GRANT SUPPORTS:PIP No. 11220100100126/11, CONICET.