IMBECU   20882
INSTITUTO DE MEDICINA Y BIOLOGIA EXPERIMENTAL DE CUYO
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Hypothalamic Neurosteroidogenesis: new regulatory mechanisms of neuroendocrine functions
Autor/es:
CABRERA, RICARDO; YUNES, ROBERTO; GIULIANI, FERNANDO; BAZZOCHINI, VANESA; LACONI, MYRIAM
Lugar:
Viña del Mar
Reunión:
Workshop; US-LATIN AMERICAWORKSHOPInNEUROENDOCRINOLOGY; 2011
Institución organizadora:
Sociedades Cientificas de Biologia de la reproduccion y endocrinologia
Resumen:
Hypothalamic Neurosteroidogenesis: new regulatory mechanisms of neuroendocrine functions Cabrera R., Yunes R; Giuliani F., Bazzocchini V. , Laconi M., Instituto de Investigaciones Biomédicas (INBIOMED-IMBECU-CONICET) Universidad de Mendoza. Argentina Neuroactive steroids and neurosteroids are steroidal molecules capable of regulating neuronal activity. Exert a potent modulatory effect at presynaptic and postsynaptic level on various receptors neurotransmitter systems such as GABA, acetylcholine, norepinephrine, serotonin, dopamine, glutamate and others. These modulatory effects determine the control of numerous physiological and pathophysiological functions of such behavioral, neuroendocrine and metabolic. Among the most studied neurosteroids are pregnenolone and its sulfate variant, progesterone and its metabolite allopregnanolone, dehydroepiandrosterone and its sulfate variant and deoxycorticosterone. In our research group we focus the study of the possible mechanisms of action of neurosteroids in different brain areas. From a multidisciplinary approach, we studied the effects of allopregnanolone, in the CNS, as well as the differential reactivity to other neurosteroids as pregnanolona and pregnanolona sulphate. I am going to present the evidence obtained specifically with some of these neurosteroids with special attention to the hypothalamus and some evidence in the striatum. In addition these lecture focus taking into account the genomic actions induced by the endogenous variables of circulating sex hormones in both males and female in different reproductive conditions such as puberty, pregnancy and estrous cycle in a close relationship with the non-genomic action of these neurosteroids. Among the most interesting conclusions reached in our group I want to mention: 1) A novel mechanism that could involve allopregnanolone on LHRH release. In addition to classical action of allopregnanolone on GABAA receptors, we suggest that allopregnanolone enhancing modulatory action on NMDA receptors; and a direct effect of allopregnanolone on LHRH release and the neuronal network afferent to LHRH, involving glutamatergic system. 2) That on certain days of pregnancy, there is a lowering of the threshold for glutamate stimulation of nigroestriatal dopaminergic nerve terminals and this may be a consequence of fluctuations in the responses of both the glutamatergic and dopaminergic systems to the activity of gonadal hormones. 3)Allopregnanolone induces changes in dopamine and GABA activity in the POA and the MBH. These changes may be involved in the inhibition of sexual receptivity and/or gonadotropin release and highlight the role of the neurosteroids as an active modulator of the reproductive patterns in the female rat. 4)The known regulatory mechanism of  hypothalamic neurotransmission, involving noradrenergic, glutamatergic and GABAergic systems, must add to astrocytes and oligodendrocytes, producing neurosteroids, which through its modulatory action mechanism regulating the reproductive function in males and females. These studies  were financially supported by grants of National Research Council of Argentina (CONICET, PIP 5942), the and University of Mendoza-Argentina (Grant 113/07).