[Microcirculatory changes in the mesentery and skeletal muscle of the rat in relation to systemic arterial pressure during stimulation of the hypothalamic nuclei].

In acute experiments on anesthetized rats, hypothalamus sites were stimulated through bipolar electrodes. Vasomotor reactions and blood flow in mesenteric and spinotrapezius muscle vessels were studied and recorded by intravital microscopy and microphotography. Systemic blood pressure (BP) was measured in the carotid artery via a catheter. The results indicate that electric stimulation of different hypothalamus sites induces pressor, depressor or biphasic BP reactions that are related to the site stimulated. Microcirculatory changes were monotonous. Regardless of BP reaction in the microcirculatory network of the mesentery, the transient acceleration, slowdown and stoppage of the blood flow were observed in mesenteric microvessels (10--70 micrometer) without changes in their diameter. Pronounced constriction of the diameter of small arteries (90--250 micrometer) were also recorded in the mesentery. During BP pressor reaction the dilatation of microvessels (5--40 micrometer) of the skeletal muscle and an increase in their blood content were noted.