The dorsal nucleus of the vagus as a centre controlling gastric motility in sheep.

Abstract

1. A preparation is described for investigating the central nervous control of gastric motility in decerebrate decerebellate sheep.2. The dorsal vagal nucleus has been electrically stimulated in thirty decerebrate sheep, and the effect on the mechanical responses of the different parts of the reticulo-rumen have been determined.3. In the absence of recurrent rhythmic gastric contractions, punctate electrical stimulation of the dorsal vagal nucleus did not elicit gastric contraction until the intensity of stimulation was sufficiently high to excite efferent vagal fibres.4. Direct stimulation of the vagus nerve, or of motor fibres running from the nucleus to this nerve, always caused contraction of the reticulum, and dorsal and ventral ruminal sacs.5. Electrical stimulation of certain points within the medulla oblongata, during rhythmic gastric motility, inhibited motility for one or more contraction cycles. These inhibitory points lay on a line commencing at the mid-point of the dorsal vagal nucleus, and extending forward and ventral to this.6. Excitatory responses were less frequent, and were seen along a line running parallel to, but about 1 mm below, the anterior half of the line of maximum inhibition. They usually followed a period of inhibition, were generally shorter in duration, and consisted of a series of small reticular contractions at a rate of about 1/10 sec.7. The presence of a powerful inhibitory influence on the dorsal vagal nucleus, mediated from an area lying anterior to the nucleus, is argued and its probable action at the level of the gastric motor nucleus is discussed.