Electrophysiological characteristics of tension receptors in the abomasal antrum of sheep

Abstract

Unitary impulse activity from tension receptors in the abomasal antrum in sheep anaesthetized with chloralose was studied with concurrent measurements of isometric tension in the antral wall, intraluminal pressures and electromyography (EMG). Rhythmical background activity had a close correlation with intraluminal pressure changes and usually a close correlation with local increases in EMG activity and isometric tension. Impulse frequencies increased, but were not sustained, following changes from isotonic to isometric conditions. Tension receptors were excited by transmural compression, by antral distension and by local intra-arterial injections of acetylcholine (2.5-25 micrograms), pentagastrin (10-20 micrograms), 5-hydroxytryptamine (1-20 micrograms), adrenaline (10 micrograms) cholecystokinin-8 (1-5 micrograms) or bradykinin (0.5-20 micrograms), and by systemic injections of bethanecol (5-1000 micrograms). Local intra-arterial perfusions of atropine (50 micrograms) and hexamethonium (100 micrograms) did not abolish spontaneous antral movements or affect the enhanced impulse activity evoked by acetylcholine or 5-hydroxytryptamine. Most antral tension receptors were excited by increases in antral tension or passive distension; they therefore functioned 'in series' with the muscularis externa. The discharges of three tension receptors were 'off-loaded' early during the contraction evoked by local injections of pentagastrin (10-20 micrograms).

Effect of Cholecystokinin-Octapeptide and Cerulein on Phasic and Tonic Components in Ovine Duodenum with Special Reference to the 'Minute Rhythm'

“…Other reports suggest that CCK and related peptides increase tonic contractions in the small bowel of monogastrics (Dollinger et al 1975;Niederau and Karaus 1991;Stacher et al 1984;Stewart and Burks 1977) but other authors did not make this observation (Anuras and Cooke 1978;Gutiérez et al 1974). It is possible that this effect could be evoked by excitation of tension receptors by CCK (Cottrell and Reynolds 1994). Thus, the stimulation of the tonic component of MR in the ovine small bowel by CCK is a new finding, although such effect can be expected.…”

“…This hormone exerts multiple physiological and pharmacological actions (W alsh 1994) and disturbances of its release and responsiveness accompany several motility disorders (Chua and Keeling 2006;Di Francesco et al 2005;Jensen 2002). CCK is also active in ruminants and affects the gastrointestinal motility directly or indirectly and this action involves both central and peripheral mechanisms (Cottrell and Reynolds 1994;Harvatine and Allen 2005;Kania et al 2006;Onaga et al 1997;Romaƒski 2004;Zavros and Shulkes 1997). CCK is known to evoke the long-lasting tonic contraction in the gallbladder (B ehar et al 2006).…”

Vagal reflex inhibition of motility in the abomasal body of sheep by antral and duodenal tension receptors

“…The general details of surgery, maintenance and monitoring of physiological parameters are described by Cottrell and Reynolds (1994).…”

“…Transmural compression was applied using circular compression plates with a surface area of 28 cm 2. These procedures are known to excite vigorously antral tension receptors (Cottrell and Reynolds, 1994). Tension in the muscularis externa was measured with serosally applied force transducers constructed from 0.5 cm 2 foil strain gauges (120 ohm; Showa Measuring Inst.…”

“…There is neural control of abomasal emptying and motility by duodenal sensory receptors in the pre-ruminant calf (Bell, 1978;Bell and Watson, 1976;Bell et al, 1981) and adult sheep (Phillipson, 1952;Ruckebusch, 1976;Gregory, 1987), but little is known of the mechanisms involved (Cottrell and Gregory, 1991). Some electrophysiological characteristics of duodenal and abomasal enteroceptors are known (Harding and Leek, 1972;Cottrell and Iggo, 1984;Cottrell and Reynolds, 1994).…”