Arterial and venous responses to hypothalamic stimulation in the dog.

Stimulation of the ventro-medial nucleus of the hypothalamus induces active constriction of both pre- and post-capillary vessels in the dog's hindlimb. Alpha-adrenolytic agents reduce these responses, indicating that they are mediated by the sympathetic nervous system. Stimulation of the paraventricular nucleus dilates both resistance and capacitance vessels. The present study demonstrates that hypothalamic neurones can control venomotor tone.