The ways through which the hypothalamic paraventricular nucleus (PVH) and the medial hypothalamus affect the organism's defence function.

In the rats, mechanical lesion or isolation of the PVH either alone or together with the medial hypothalamic sympathetic area, which includes hypophyseotropic area, too, induces a long lasting decrease of the total number of leukocytes and of the most components of the leukocytary formula, which are attributed mainly to the decreased sympathetic tonus, induced by medial hypothalamus disconnection.