Effects of vagotomy on entrainment of activity rhythms to food access.

Subdiaphragmatic vagotomy had little effect on anticipatory wheel running in rats maintained on 4 hr of food access per day. In ad lib conditions, sections of the anterior trunk of the vagus reduced total activity, but did not substantially affect its nocturnal distribution. During restricted feeding, rats with anterior trunk sections showed amounts of anticipatory wheel running comparable to controls, while vagotomized rats with suprachiasmatic nucleus (SCN) lesions showed a reduced amount of activity. After the posterior trunk was sectioned, as well, or after combined sections, there was little change in the amount of anticipatory activity but a significant increase (1 hr) in the duration. In control rats, the duration of anticipatory activity showed a nonsignificant decrease over 50 days on restricted feeding. Neither the vagus nerve, nor the SCN, are essential for the entrainment of activity to restricted feeding.