In vitro responses to noradrenaline of small intestine taken from normal and grass sickness-affected horses.
Abstract: Small intestine was taken from the caudal flexure of the duodenum and the terminal ileum proximal to the ileocaecal fold of 25 horses, 9 with acute grass sickness (AGS), 12 with subacute grass sickness (SAGS) and 12 with chronic grass sickness (CGS). The motility in the samples was measured isometrically either within 1 h of death or after storage for 24 h at 4 degree C. In control tissue, noradrenaline produced contractions of muscle strips which did not involve a muscarinic cholinergic mechanism and which were unaffected by the alpha 1 antagonist prazosin but were blocked by the alpha 2 antagonist yohimbine. Pretreatment with the alpha antagonist phentolamine prevented the contractile response to noradrenaline and the background contractions either continued at a reduced rate and amplitude or were abolished after a few minutes. Thus, following alpha blockade, noradrenaline reduced the background contraction rate by an effect on inhibitory beta adrenoceptors. The rate of background contractions in duodenal preparations was significantly greater than that in control ideal preparations. Although cold storage for 24 h caused a reduction in the background contraction rates of the control preparations, there was no effect on the contractile responses to noradrenaline, the associated pharmacology being similar to that of fresh tissue. This suggests that noradrenaline-evoked contraction was not dependent on enteric neural elements. The response to noradrenaline by grass sickness-affected tissue was generally similar to that of tissue from control horses, with an immediate contraction which was alpha 2 sensitive. The contractile response to noradrenaline after propranolol was significantly reduced in the CGS group and there were significant differences between the AGS, CGS and control groups. There was a significant difference between the ileal preparations from the control and SAGS groups in their response to noradrenaline following pretreatment with propranolol.
Publication Date: 1998-01-28 PubMed ID: 9444080DOI: 10.1023/a:1005923015366Google Scholar: Lookup
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- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research paper investigates how noradrenaline affects the small intestine tissues in horses suffering from grass sickness. It analyzes the muscle movements in tissue samples from healthy horses and those with different stages of grass sickness after exposure to noradrenaline and several antagonists.
Samples and Experiment Methodology
- Small intestine samples were collected from 25 horses – 9 with acute grass sickness (AGS), 12 with subacute grass sickness (SAGS), and 12 with chronic grass sickness (CGS).
- The motility, or ability to move spontaneously, in these samples was measured within one hour of death or after being stored for 24 hours at 4 degrees Celsius.
Noradrenaline Impact on Control Tissue
- In the control tissue, noradrenaline produced contractions of muscle strips through a mechanism that did not involve muscarinic cholinergic interaction.
- The contractions were not affected by the alpha 1 antagonist prazosin, but were halted by the alpha 2 antagonist yohimbine.
- Pretreatment with the alpha antagonist phentolamine led to the prevention of the contractile response to noradrenaline and the background contractions were reduced or completely halted.
- This indicates that after alpha blockade, noradrenaline reduced the background contraction rate through a beta adrenoceptors inhibitory effect.
- The rate of background contractions in duodenal preparations was significantly greater than those in control ileal preparations.
Impact of Cold Storage
- Storage at low temperature for 24 hours caused a reduction in the background contraction rates of the control preparations, but did not influence the contractile responses to noradrenaline.
- These findings suggest that the noradrenaline-triggered contraction was not reliant on enteric neural elements.
Noradrenaline Response in Grass Sickness-affected Tissues
- The response to noradrenaline in tissues from grass sickness-affected horses was mostly similar to that from healthy horses, with an immediate contraction that was sensitive to alpha 2.
- However, in the CGS group, the contractile response to noradrenaline, after propranolol, was significantly reduced.
- Significant variations were identified between the AGS, CGS, and control groups.
- Moreover, a significant difference was observed between the ileal preparations from the control group and the SAGS group in their response to noradrenaline following pretreatment with propranolol.
Cite This Article
APA
Murray A, Pearson GT, Cottrell DF.
(1998).
In vitro responses to noradrenaline of small intestine taken from normal and grass sickness-affected horses.
Vet Res Commun, 21(8), 571-585.
https://doi.org/10.1023/a:1005923015366 Publication
Researcher Affiliations
- Department of Preclinical Veterinary Sciences, Royal (Dick) School of Veterinary Studies, University of Edinburgh, UK.
MeSH Terms
- Adrenergic alpha-Agonists / pharmacology
- Adrenergic alpha-Antagonists / pharmacology
- Animals
- Autonomic Nervous System Diseases / physiopathology
- Autonomic Nervous System Diseases / veterinary
- Dose-Response Relationship, Drug
- Duodenum / drug effects
- Duodenum / physiology
- Epinephrine / pharmacology
- Female
- Horse Diseases / physiopathology
- Horses
- Ileum / drug effects
- Ileum / physiology
- In Vitro Techniques
- Intestine, Small / drug effects
- Intestine, Small / physiology
- Male
- Muscle Contraction / drug effects
- Muscle Contraction / physiology
- Muscle, Smooth / drug effects
- Muscle, Smooth / physiology
- Norepinephrine / pharmacology
- Phentolamine / pharmacology
- Prazosin / pharmacology
- Time Factors
- Yohimbine / pharmacology
References
This article includes 19 references
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Citations
This article has been cited 1 times.- Verhaar N, Hoppe S, Grages AM, Hansen K, Neudeck S, Kästner S, Mazzuoli-Weber G. Dexmedetomidine Has Differential Effects on the Contractility of Equine Jejunal Smooth Muscle Layers In Vitro.. Animals (Basel) 2023 Mar 10;13(6).
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