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Title: Neural mechanisms in abomasal motility
Author: Stanley, Hugh Gerard
ISNI:       0000 0001 3477 458X
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1988
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1. The motor profile of the exteriorized abomasal body and antrum of chloralose-anaesthetized adult sheep, recorded using balloon catheters and e.m.g. electrodes, consisted of tonic muscular activity upon which contractile muscular activity could be superimposed. The different motility patterns of the body and antrum suggest that they are separate functional entities. 2. Transection of the exteriorized abomasum into separate body and antral pouches significantly increased antral contraction amplitude and significantly decreased body tone. This suggests that in the intact preparation the body exerts an intrinsic inhibitory drive to antral contraction amplitude, and that either the antrum exerts an intrinsic excitatory drive to body tone or increased antral contraction amplitude results in an extrinsic inhibitory drive to body tone. 3. Repetitive electrical stimulation of the cut peripheral end of the cervical vagus ( 1-10 Hz, 1-50 V, 1 ms pulse duration for 10 s) caused body relaxation in 5 out of 7 preparations. Higher frequency electrical stimulation (10- 50 Hz) caused body contraction. In 4 preparations electrical stimulation (1-50 Hz, 1-50 V, 1 ms pulse duration for 10 s) of the cut peripheral end of the cervical vagus caused antral contraction. In 3 ostensibly identical preparations similar electrical stimulation reduced antral contraction amplitude. Thus evidence was found for vagal excitatory and inhibitory innervation of the abomasal body and antrum, and for an integrative mechanism at the intramural level. 4. Body pouch inflation increased antral contraction amplitude by a vagally-dependent mechanism, and decreased the discharge rate of 10 out of 33 efferent units isolated from abdominal branches of the vagus within 2 cm of the antrum. If the decrease in unitary discharge is instrumental in increasing antral contraction amplitude it is likely that the units have inhibitory function. 5. The slight body pouch relaxation produced by body pouch inflation was not altered by extrinsic denervation. Inflation of an intra-reticular balloon produced similar effects on the abomasal body motor profile as inflation to the same volume of an intra-abdominal balloon placed beside the reticulum. Thus no evidence was found for a functional reflex corresponding to receptive relaxation found in the monogastric animal. 6. The response of 33 efferent units, dissected from the abdominal continuations of the dorsal and ventral vagi within 2 cm of the antrum, to inflation of the abomasal body pouch, and to systemic injection of 100 ug of adrenaline was investigated. All units responding to body pouch inflation also responded to adrenaline injection. Unitary discharge was analysed for temporal relationships with antral e.m.g. activity and the e.c.g. using a post stimulus time histogram technique. Units showing discharge association with the antral e.m.g. also showed discharge association with the e.c.g. Thus in the sheep neither discharge response to discrete stimulation of specific receptor populations nor the presence of system-related rhythms in efferent discharge is necessarily indicative of efferent destination or function.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Sheep stomach motor control