Coupling between hypothalamic alpha 2-adrenoceptors and [3H]mazindol binding site in response to several hyperglycaemic stimuli in mice.

The hypothalamic response to circulating glucose and insulin levels was studied in the mouse by differentially attenuating glucose-homeostasis. The administration of glucose, 2-deoxyglucose or the alpha 2-adrenoceptor agonist UK 14.304 was accompanied by a persistent hyperglycaemia; however, an increase in insulin levels was obtained with glucose and a decrease with the other two manipulations. Both alpha 2-adrenoceptors (labeled with [3H]idazoxan) and the anorectic recognition site (labeled with [3H]mazindol) were upregulated by the three treatments. A good correlation was obtained between circulating glucose levels and either hypothalamic [3H]mazindol binding (r = 0.70, P less than 0.001) or [3H]idazoxan binding (r = 0.63, P less than 0.001), as well as between the two binding sites (r = 0.88, P less than 0.001). No correlation was obtained between circulating insulin levels and these binding sites (r = 0.18, r = 0.26, P = n.s. for [3H]mazindol and [3H]idazoxan binding, respectively). It is suggested the alpha 2-adrenoceptors and the anorectic binding sites are associated in their response to glucose as part of a hypothalamic center involved in the regulation of feeding mechanisms.