Effect of ventromedial hypothalamic stimulation on blood flow of brown adipose tissue in rats.

The changes in regional blood flows to the rat's interscapular brown adipose tissue and several other tissues during electrical stimulation of the ventromedial hypothalamus (VMH) were studied using radioactively labelled microspheres. Measurement of blood flow was carried out, along with monitoring heart rate, under anesthesia and at thermoneutrality. During VMH stimulation the heart rate was clearly augmented and cardiac output increased about 45%. Regional blood flows were significantly increased in response to VMH stimulation in interscapular brown adipose tissue, adrenal glands, diaphragm and gastrocnemius muscles. The response of interscapular brown adipose tissue was the most prominent (approx. fifty-fold increase). Blood flows tended to decrease in spleen, lungs and kidneys during VMH stimulation, but did not change in liver or in other visceral organs. These observations suggest that the VMH is concerned with the regulation of regional blood flow to brown adipose tissue and contributes to thermogenesis in this tissue.