Effects of Lesions of the Red Nucleus on Feeding and Drinking in Rats

We have examined the effect of a unilateral chemical lesion, made in the red nucleus (RN), on feeding and drinking in rats. Kainic acid (0.1 μL, lesion group) or phosphate-buffered saline (0.1 μL, control group) was injected into the left RN. Before injection there was no significant difference between lesion and control groups in the mean number of pellets ingested, the mean number of pellets dropped from the mouth, or the mean number of water drops drunk. The mean number of pellets ingested and the mean number of water drops drunk fell significantly after injection in the lesion group, and then returned to pre-injection levels. Dropping pellets increased greatly in the lesion group after injection. Rats in the lesion group would grasp a pellet and put it into their mouth, but they often did not chew the pellet, or chewed it several times and then dropped it from their mouth. Our study indicates that rats with lesions of the RN cannot chew food and drink well, and that ingestion of food and water decreases temporarily.