Neonatal infraorbital nerve damage and the development of eating behavior in the rat

It has been previously shown that bilateral infraorbital nerve (ION) transection in adult rats has little effect upon body weight regulation or eating behavior. However, in neonatal mouse, unilateral ION cut produces a profound decrease in body weight, beginning around the time of weaning. To help clarify the role of the ION in the development and sensorimotor control of eating solid food in rodents, the present experiment examined the effects of unilateral, neonatal ION transection in rats, upon body weight regulation and post-weaning eating behaviors. Comparison of normal and lesioned groups of rats, up to postnatal day (PND) 61, revealed no significant difference in mean adjusted (for sex) body weight. In addition, no significant differences were detected between the groups on post-weaning (PND 26 to PND 61) measures of mean adjusted (for weight) food intake, responsiveness to food, biting ability or inefficiency of mandibulation. At the end of the experiment, the effectiveness of the lesion was histologically evaluated. A significant 48.5% mean reduction in the cross-sectional area of the ophthalmic-maxillary portion of the trigeminal ganglion was observed on the lesioned side, relative to the intact side. There appears to be a differential influence of unilateral, neonatal ION cut upon eating in rat and mouse.