Contrôle hormonal et nutritionnel des neurones hypothalamiques galaninergiques chez le rat
(1997)
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- In mammals, hypothalamic galanin is a key regulator of pituitary-dependent hormones and also regulates feeding behaviour. It would thus be expected that pituitary-dependent functions as well as nutrients can in turn regulate the activity of galaninergic neurons. <BR> We show that hypophysectomy modifies the activity of hypothalamic galaninergic neurons. Furthermore, the response to hypophysectomy is strikingly different in the neurohypophyseal and the hypothalamo-pituitary axis. In the former, hypophysectomy induces, through a seemingly lesion effect, alarge – although transient – increase in galaninergic immuno eactivity. In the latter, hypophysectomy is followed by a persistent decrease of galaninergic immunoreactivity, that can be prevented by multiple pituitary hormone substitution. Serial single hormone substitution shows that different hormonal axes, for instance the somatotropic and gonadotropic axes, exert feed-back regulations on galaninergic immunoreactivity in specific populations of hypothalamic neurons. <BR> Galanin is also involved, with neuropeptide Y, in the stimulation of feeding behaviour. We studied changes in hypothalamic expression of galanin and neuropeptide Y during cyclic anorectic feeding behaviour induced by zinc-deprivation in rats. This is accompanied by an increased expression if neuropeptide Y mRNA, suggesting the presence of neuropeptide Y resistance in zinc deprivation. Hypothalamic galanin mRNA on the other hand progressively decreases in zinc deprivation, likely from inhibitory influence of this condition on somatotropic axis activity. In this model, we also describe the nutritional regulation of neuropeptide Y-immunoreactivity in the suprachiasmatic nucleus, which could constitute the anatomical substrate of biological rhythms regulation by timed feeding. <BR> Thus, the hypothalamic galanin system appears functionally heterogeneous and composed of distinct functional subpopulations submitted to distinct feed-back regulations
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Selvais, P. L. (1997). Contrôle hormonal et nutritionnel des neurones hypothalamiques galaninergiques chez le rat. https://hdl.handle.net/2078.5/111293