Diferencas na secrecao diaria de leptina em homens e mulheres: possiveis implicacoes na neuroendocrinologia dos transtornos alimentares / Daily secretion differences of leptin in men and women: neuroendocrinology possible implications of eating disorders

Introducao: alteracoes de cortisol e hormonios sexuais sao frequentes em transtornos alimentares. Leptina atua no sistema adrenal/gonadal e sinaliza saciedade para o cerebro. Estudos recentes demonstraram alteracoes de leptina em mulheres com anorexia nervosa e bulimia nervosa. Objetivos: 1) verificar se ha uma diferenca no padrao de secrecao diaria de leptina entre sexos; 2) comparar hormonios sexuais e leptina em mulheres. Metodo: a leptina plasmatica foi medida em oito homens e seis mulheres normais. Series temporais compostas de valores plasmaticos de leptina, LH (hormonio luteinizante) e estradiol foram avaliados por testes de deteccao de pulsos, analise espectral e cross-correlation. Resultados: a leptina diaria e a amplitude dos pulsos de leptina sao duas vezes maiores nas mulheres que nos homens...

The role of nitric oxide (NO) in control of hypothalamic-pituitary function

Neurons containing neural nitric oxide synthase (nNOS) are found in various locations in the hypothalamus and, in particular, in the paraventricular and supraoptic nuclei with axons which project to the median eminence and extend into the neural lobe where the highest concentrations of NOS are found in the rat. Furthermore, nNOS is also located in folliculostellate cells and LH gonadotropes in the anterior pituitary gland. To define the role of NO in the release of hypothalamic peptides and pituitary hormones, we inected an inhibitor of NOS, Ng- monomethyl-L-arginine (NMMA) or a releasor of NO, nitroprusside (NP) into the third ventricle (3V) of conscious castrate rats and determined the effect on the release of various pituitary hormones. In vitro, we incubated medial basal hypothalamic (MBH) fragments and studied inhibitors of NO synthase and also releasors of NO. The results indicate that NOergic neurons play an important role in stimulating the release of corticotrophin-releasing hormone (CRH), luteinizing hormone releasing-hormone (LHRH), prolactin-RH's, particularly oxytocin, growth hormone-RH (GHRH) and somatostatin, but not FSH-releasing factor from the hypothalamus. NO stimulates the release of LHRH, which induces sexual behavior, and causes release of LH from the pituitary gland. The intrahypothalamic pathway by which NO controls LHRH release is as follows: glutamergic neurons synapse with noradrenergic terminals in the MBH which release nonepinephrine (NE) that acts on alpha1 receptors on the NOergic neuron to increase intracellular free Ca++ which combines with calmodulin to activate NOS. The NOS diffuses to the LHRH terminal and activates guanylate cyclase (GC), cyclooxygenase and lipoxygenase causing release of LHRH via release of cyclic GMP, PGE2 and leukotrienes, respectively. Alcohol and cytokines can block LHRH release by blocking the activation of cyclooxygenase and lipoxygenase without interfering with the activation of GC. GABA also blocks the response of the LHRH neurons to NO and recent experiments indicate that granulocyte macrophage colony-stimulating factor (GMCSF) blocks the response of the LHRH neuron to NP by activation of GABA neurons since the blockase can be reversed by the competitive inhibitor of GABAa receptors, bicuculine.