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Title: Duodenal sensory and reflex mechanisms
Author: Cottrell, David F.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1981
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Duodenal sensory and reflex mechanisms were examined during acute experiments with isolated loops of duodenum in anaesthetised rabbits and sheep. Mechanical stimulation of the rabbit duodenum caused reflex motor responses in adjacent segments of the gut. The thresholds of these reflexes were the same as the thresholds of mechanoreceptors whose afferent activity was recorded in duodenal nerves during electrophysiological investigations. These mechanoreceptors were situated in the muscularis externa, the serosa and the mesentery. Mechanoreceptors in the muscularis externa were excited when the duodenum was perfused with chemical solutions containing glucose. In the sheep duodenum the impulse activity of afferent units from slowly adapting mechanoreceptors in the muscularis externa coincided with local electromyographic (emg) and tension changes. Units were excited by passive distension, compression, active increases in muscle tension and alterations of temperature. The application of chemical solutions or light mechanical stimulation of the mucosa evoked intrinsic reflexes which modified impulse activity. Receptors were excited by injections of peptide hormone analogues and other drugs. With the exception of insulin, the responses evoked by drugs coincided with increases in muscle tension and emg activity. Slowly adapting mechanoreceptors in the sheep duodenal mucosa were either silent in the absence of a mechanical stimulus or were spontaneously active. Mucosal receptor units were selectively sensitive to chemicals. One class of unit was excited by solutions of potassium chloride and another was excited by volatile fatty acids. No evidence was found for mucosal receptors sensitive to osmolality or temperature changes. It was concluded that : (a) the mechanoreceptors in the muscularis externa of the sheep duodenum are tension receptors which occupy a position "in series" with longitudinal muscle; (b) post-prandially released alimentary hormones may increase impulse activity in duodenal tension receptors and thus, by a reflex mechanism, modify gestive behaviour and gastric emptying; (c) spontaneously active mucosal receptors are associated with contractile elements in the muscularis mucosa; (d) the responses of mucosal receptors to chemicals in duodenal chyme makes them poor candidates for providing tonic afferent inputs to the central nervous system; (e) these mucosal mechanoreceptors do not initiate reflexes requiring large mechanical stimuli; and (f) the sensory receptors studied do not play a part in duodenal reflex mechanisms initiated by osmotic changes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available