Unique contribution of catecholamine receptors in the brain of the cat underlying feeding

After a Collison cannula was implanted bilaterally in the cat for intracerebroventricular (ICV) injection, individual patterns of food intake were determined. A mixture of dry and canned cat food was provided to the animal every morning at the same time for 1.0 hr. Once intakes had stabilized, either norepinephrine (NE) or an adrenoreceptor blocking agent was infused in one lateral ventricle by gravity flow over an interval of 30-60 sec. NE given ICV in a dose of 25-75 micrograms 15 min before the period of feeding enhanced both the amount of food consumed by the cat and the duration of its feeding for up to 1.0 hr. When phentolamine in a dose of 25-100 micrograms was infused 15 min prior to the feeding interval, the cat's intake of food was attenuated in a dose-dependent manner, again in terms of both the quantity consumed and the interval of eating. Propranolol was essentially without effect on food intake. In the fully satiated cat, NE infused ICV 15-45 min following the termination of its morning feeding episode tended to augment food intake at the highest 100 micrograms dose, but the effect was not significant. The dose-dependent hypothermia typically observed after NE is given ICV to the cat was found to be entirely independent of the feeding response. Overall, these findings show that noradrenergic pathways in the cat's feeding system apparently bias or otherwise modulate the amount of food consumed. As in other species, the feeding mechanism appears to be mediated through alpha-adrenergic receptors presumed to be in the diencephalon of the cat.