Summary.States of hunger and satiety are under ischymetric (i. e., rate of cellular energy production) control which depends on both substrate availability and hormonal composition. The latter varies in response to external (olfactory, gustatory and gastrointestinal) stimuli sensed by specific receptors and projected on lateral hypothalamic (LH) units from which departs the descendant control pathway of metabolic glands. This neurohormonal loop is responsible for the anticipatory glycemic and other changes observed during a meal and the preabsorptive "satiation" ending the meal long before the postabsorptive cellular repletion will induce the state of more permanent "satiety". New data on LH "sweet" taste projection and hypothalamo-pancreatic control are shown and strengthen the above view.Key words: Oro-glycemic reflex, hypothalamic taste units, preabsorptive satiation, insulin, glucagon, metabolism.
Ischymetric Dependence of Hunger and SatietyAlthough homeorheusis 1 of glycemia is achieved through continuous utilization of endogenous reserves, the ultimate source of replenishment is located in the environment and has to be behaviorally acquired. In fact, numerous observations of feeding in animals [25], and reports of hunger [28] in humans in relation to severe hypoglycemia led to the concept of a glucostatic mechanism of feeding and to its immensely seminal description as the glucostatic theory by Jean Mayer [23, 24]. The subsequent failure to explain persistent feeding in spite of large 1 Homeorheusis: the dynamic version of homeostasis, where rheusis (in Greek: flow) replaces stasis (in Greek: stagnation). It designates the maintenance of a value at a level which may vary, but only according to a biologically determined program, such as circadian or annual rhythms intravenous (iv) loads of glucose [1,2, 20, 51], together with the same reasoning for lipids and amino acids, led to other sorts of "molecular static" theories (for rev. see [59]). All of them were justified by some reasonably good experimental evidence. Today, this partial validation of all of the previous hypotheses is explained by the ischymetric (ischys: power or rate of energy production) hypothesis [34, 38] which proposes that the ultimate stimulus of the specific arousal of hunger is the drop below a critical level of power production in specific diencephalic cells sharing the general metabolism of the body.The hypothalamus can be considered from the metabolic point of view as a microcosm of the somatic macrocosm. Hypothalamic units are constantly informed of the repletion/depletion state of the inner milieu (for rev. see [44]) and, at the same time, of recent ingestants [31, 32]. Taking into account the actual situation of energogenic reserves (adipose and other) and potential repletion (ingestants), hypothalamic units produce their own metabolic hormones [14, 58] and modulate the release of metabolic hormones from peripheral glands. The hypothalamus receives much more information than the plasma-concentration-oriented pancreatic endoc...