The central vs. peripheral effects of clonidine on ACTH, corticosterone and glucose release.

The role of central vs. peripheral actions of clonidine was investigated in the rat following the separate and combined administration of clonidine and 2-deoxy-D-glucose (2-DG). Clonidine or 2-DG alone stimulated serum glucose and corticosterone but hypothalamic noradrenaline neuronal activity and ACTH release were stimulated by 2-DG only. The stimulation of noradrenaline neuronal activity and ACTH by 2-DG were totally blocked by clonidine. It was concluded that the increases in serum glucose and corticosterone after clonidine administration were not mediated by central effects but that alpha 2-adrenoceptor agonism by clonidine was responsible for inhibition of hypothalamic noradrenaline neuronal activity and pituitary ACTH release.