Reflex co‐ordination of corporal and antral contractions in the conscious dog

Abstract

SUMMARYThis study characterizes the role of extrinsic nerves in the co-ordination of corporal and antral contractions in the dog. Fasting motor activity was recorded in conscious dogs with stomachs previously divided into separate corporal and antral pouches. Both corpus and antrum showed synchronized phases of activity and quiescence recognizable as migrating motor complexes (MMCs, duration 81-2 + 9-6 min, n = 4). Moreover, individual contractions were temporally linked such that corpus contractions, occurring at 76+4 s intervals, were each followed by a burst of one to three antral contractions at a frequency of 4-5 min-'. The mean latency between the onset of individual contractions in the corpus and antrum was 109 + 2-6 s (n = 4). Denervation of the antral pouch in two additional dogs did not affect the MMC cycle (mean durations 106-6 and 82 1 min) and the onset of activity in the corpus and antrum was generally co-ordinated but less precise. However, individual antral contractions were no longer linked to corporal contractions, occurring randomly throughout the corpus contraction cycle. This was associated with a lower contraction frequency in the denervated antral pouches than in the corpus (0 3 + 0-1 min-' compared to 0 6 + 0 08 min-'). It is proposed that a vagal reflex, excited by corporal tension receptors, provides phasic excitation facilitating the generation of antral contractions. Such a reflex is likely to reinforce the myogenic mechanisms which occur in the intact stomach and thus plays a role in co-ordinating gastric peristalsis.

Gastrointestinal peristalsis: Joint action of enteric nerves, smooth muscle, and interstitial cells of Cajal

“…A well-studied motor pattern involving rhythmic activity of the enteric nervous system is the ''migrating myo-electric complex'' or MMC, which occurs in the empty stomach and intestine. The initiation of the MMC resides in the enteric nervous system and in part the CNS through vagal pathways (Hall et al, 1982(Hall et al, , 1984Rudge et al, 1990;Sarna et al, 1984;Szurszewski, 1969). In humans, every 1.5 hours a section of stomach or intestine receives intense stimulation from cholinergic motor neurons that derive from the vagus or the enteric nervous system.…”

Selective loss of vagal intramuscular mechanoreceptors in mice mutant for steel factor, the c-Kit receptor ligand

“…For example, distension of the entire stomach or just the corpus stimulates antral contractions, an effect that is blocked by vagal transection (Andrews et al 1980;Rudge et al 1990). Moreover, vagal nerve branches (most probably their afferent components) that selectively innervate the proximal stomach are responsible for activating at least some of these more distal motor responses (Oliveira et al 1985;Lee et al 1995).…”

“…Additionally, since forestomach IMAs are amongst the first receptors to detect accumulation of food in the stomach, they appear to contribute to the vagal afferent limb of important digestive reflexes that could influence the pattern of food intake. These reflexes include accommodation, peristaltic activity of the corpus and antrum, and gastric emptying (Canon and Lieb 1911;Grey 1917;Andrews et al 1980;Rudge et al 1990;Schwartz et al 1993;Ward et al 1994Ward et al , 1995. Therefore, as a first step toward identifying which vagal sensory functions might be affected, we compared meal patterns of steel mutants and wild-type mice.…”

An excitatory body‐antral reflex in the sheep abomasum

“…In the transected ferret stomach, with separate compartments of the gastric body and antrum, inflation of the gastric body increases the amplitude of antral contractions by a vagally dependent mechanism (Andrews et al 1980). In the conscious dog with a surgically divided stomach antral and gastric body reflexes are coordinated (Grundy, Hutson, Rudge & Scratcherd, 1989) by a mechanism lost after antral denervation (Rudge, Grundy, Hutson, Scratcherd & Kerrigan, 1990). Few studies of alimentary reflexes in adult ruminants have concentrated on abomasal motor control.…”