Norepinephrine, clonidine, and tricyclic antidepressants selectively stimulate carbohydrate ingestion through noradrenergic system of the paraventricular nucleus

Using a self-selection feeding procedure, the present experiments examined the impact of central and peripheral injection of the alpha-adrenergic agonist clonidine (CLON) and the tricyclic antidepressant drugs amitriptyline (AMIT) and chlorimipramine (CIMIP) on nutrient selection in the adult male rat. In tests with mixed diets or with separate sources of the 3 macronutrients (carbohydrate, protein, and fat) simultaneously available, the following results were obtained: Peripheral and paraventricular nucleus (PVN) injection of CLON stimulated total food intake and preferentially increased ingestion of carbohydrate. Little or no change in protein or fat intake was observed. This pattern of response is similar to that observed with norepinephrine. PVN injection of AMIT and peripheral injection of CIMIP also selectively enhanced carbohydrate intake. These drug effects on carbohydrate selection occurred under a variety of conditions, including with mixed diets and pure dietary nutrients; under ad lib and restricted feeding conditions; in short (1 hr) as well as long (6 hr) test intervals; and in the absence or presence of a change in total calorie intake. Based on this and other evidence, it is proposed that noradrenergic neurons innervating the PVN in the rat play a role in regulating carbohydrate selection, and that this neurochemical system mediates the stimulating action of CLON and antidepressants on carbohydrate ingestion.