Lateral hypothalamus mediated effects of a food signal on blood glucose concentration

Abstract

A distinctive biphasic hyperglycaemia, similar to that observed after electrical stimulation of the lateral hypothalamus in the region of the feeding system, was seen in hungry rats after a 3 min presentation of an unreinforced visual discriminative stimulus (DS) during which the rats pressed a lever for food reinforcement at variable intervals, as they had been trained under food deprivation. A monophasic hyperglycaemia was seen after presentation of the same visual stimulus to undeprived animals trained to escape or to avoid foot shock by pressing the lever during DS presentation. No appreciable blood glucose variations were seen with a water-DS under thirst or with the visual stimulus before training. Food deprivation was necessary to the oscillatory glucose response to the food-DS. The response was eliminated by injections of novocaine bilaterally through chronic intrahypothalamic cannulae which were also capable of eliciting eating when used to guide noradrenaline injections. These results provide further evidence that the feeding system mediates direct metabolic effects as well as behavioral control.