10.1. DRUGS AFFECTING
APPETITE
Satiety and hunger are regulated by the hy-pothalamus (fig. 10.1). Stimulation of a lateral hypothalamic area referred to as the hunger center leads to an increase in appetite, whereas inhibition of that center leads to food refusal. Experimental destruction of the satiety center in the medial hypothalamic area leads to unstoppable desire to devour food. The hunger and satiety centers represent an aggregate of functionally interrelated structures of the central nervous system; they regulate food behavior and coordinate the gastrointestinal function. The hunger center activity is controlled by noradrenergic neurons, whereas the satiety center activity is controlled by serotonergic neurons. Stimulation of the noradrenergic system of the brain results in suppression of the hunger center and in an increase in appetite, whereas stimulation of the serotonergic system results in activation of the satiety center and, consequently, in reduced appetite.
Along with this, there is humoral regulation of food intake which involves hormones ghrelin and leptin. Ghrelin is a peptide hormone produced by cells of the gastrointestinal tract; the concentration of this hormone increases uponfasting and decreases after food intake. This hormone regulates appetite; its high blood concentration leads to greater food intake and weight gain. On the other hand, once weight gain has occurred, ghrelin blood concentration decreases, and, consequently, weight loss occurs. Thus, ghrelin is supposedly involved in body weight regulation. Receptors tothis hormone are found in the ventromedial hypotha-lamic region and arcuate nucleus. These receptors are involved in regulation of releasing hormone production, appetite increase, changes in blood glucose levels, changes in lipid metabolism, regulation of secretion and peristalsis proceeding in the walls of the gastrointestinal tract.