Nutritional implications of cephalic phase thermogenic responses

The sensory stimulation of feeding produces a cephalic thermogenic response which coincides with an increase of plasma insulin, catecholamines and glu cagon. These responses also take place with sham feeding but not wit tube f eeding. Vagal denervation of the pancreas as well as atropine administratio n block the initial release of insulin and reduce by 50% the thermogenic re sponse and norepinephrine release. An adrenergic blocker also reduces this response by 50%. However, with the simultaneous administration of both atro pine and an adrenergic beta-blocker, this reduction is not observed. Indire ct evidence suggests that this paradox is possibly explained by an enhanced secretion of glucagon.