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Home / Equine Research Bank / Vet Res Commun / Muscarinic receptor subtypes in equine tracheal smooth muscl...
Veterinary research communications1992; 16(4); 301-310; doi: 10.1007/BF01839329

Muscarinic receptor subtypes in equine tracheal smooth muscle.

Abstract: Selective muscarinic receptor antagonists were used to identify muscarinic receptor subtypes in equine trachealis strips. The M1 receptor antagonist pirenzepine (10(-7) mol/L to 3 x 10(-5) mol/L) and the M3 receptor antagonist 4-diphenylacetoxy-N-methylpiperidine (4-DAMP, 10(-9) mol/L to 3 x 10(-7) mol/L3) dose dependently inhibited the contractile responses to electrical field stimulation (EFS) and exogenous acetylcholine (ACh). Schild plots yielded a pA2 value for pirenzepine vs ACh of 6.75 +/- 0.09, which is consistent with the affinity for M2 or M3 receptors, and a pA2 value for 4-DAMP vs ACh of 8.47 +/- 0.09, which is in agreement with the affinity for M3 receptors. The M2 receptor antagonist gallamine (10(-5) mol/L and 10(-4) mol/L) did not affect the response of trachealis to exogenous ACh and low-frequency EFS (0.1-2 Hz) but decreased the responses to high-frequency EFS (4-16 Hz). These results suggest that the muscarinic receptors mediating contractions induced by ACh in equine tracheal smooth muscle are of the M3 subtype. The lack of an increase in the response to EFS following gallamine suggests that functional prejunctional inhibitory M2 receptors are not present on the cholinergic nerves innervating equine tracheal smooth muscle.
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Publication Date: 1992-01-01 PubMed ID: 1466148DOI: 10.1007/BF01839329Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research paper investigates the types of muscarinic receptors in the smooth muscle of the horse’s windpipe, concluding that the M3 type receptor triggers contractions. No evidence was found for M2 receptors on nerve endings.

Decoding the Research Methodology

  • The research started by identifying muscarinic receptor subtypes, which are known to be involved in the function of the body’s autonomous system that regulates bodily functions not consciously directed, like breathing, heartbeat, and digestive processes.
  • The study specifically looked at the trachealis strips of an equine, the muscles associated with a horse’s windpipe. The relevance of this is because muscarinic receptors are known to influence smooth muscle activity.
  • Antagonists (substances which inhibit the function) for M1 and M3 receptors, namely pirenzepine and 4-DAMP respectively, were used. These were used in varying concentrations to inhibit the muscle’s responses to both electrical field stimulation (EFS) and acetylcholine (ACh), a neurotransmitter in the nervous system.
  • The researchers assessed the effectiveness of these inhibitors through a method known as Schild plots. Schild plots are graphical representations used in pharmacokinetics (the movement of drugs within the body) to determine the affinity of a drug for a receptor.

Findings of the Research

  • The study found that, based on the pA2 values obtained (which is an index of the antagonist’s affinity for a receptor), both antagonists were successful in inhibiting muscle responses, with results indicating that the smooth muscle contractions were influenced by M3 type receptors.
  • The researchers also used an M2 receptor antagonist, gallamine. However, the study found that it did not affect the responses, thereby suggesting that M2 receptors are not present in equine tracheal smooth muscle.
  • In conclusion, the contractions of the equine tracheal smooth muscle as triggered by acetylcholine were found to be mediated by the M3 subtype of muscarinic receptors.

Implications and Significance

  • This research is significant because it helps to further our understanding of the autonomous system functioning in equines, specifically the reflexes mediated through the muscarinic receptors in the smooth muscle of the trachea.
  • These findings could potentially be useful in veterinary medicine, particularly when it comes to treating disorders related to smooth muscle contractions, like asthma or other respiratory conditions in horses.
  • In veterinary pharmacology the study enhances the understanding of the effectiveness and potential side effects of drugs that target muscarinic receptors.

Cite This Article

APA
Yu M, Robinson NE, Wang Z, Derksen FJ. (1992). Muscarinic receptor subtypes in equine tracheal smooth muscle. Vet Res Commun, 16(4), 301-310. https://doi.org/10.1007/BF01839329

Publication

Veterinary research communications
ISSN: 0165-7380
NlmUniqueID: 8100520
Country: Switzerland
Language: English
Volume: 16
Issue: 4
Pages: 301-310

Researcher Affiliations

Yu, M
  • Pulmonary Laboratory, College of Veterinary Medicine, Michigan State University, East Lansing 48824-1314.
Robinson, N E
    Wang, Z
      Derksen, F J

        MeSH Terms

        • Acetylcholine / antagonists & inhibitors
        • Animals
        • Electric Stimulation
        • Gallamine Triethiodide / pharmacology
        • Horses / physiology
        • In Vitro Techniques
        • Muscarinic Antagonists
        • Muscle Contraction / drug effects
        • Muscle, Smooth / chemistry
        • Muscle, Smooth / drug effects
        • Muscle, Smooth / physiology
        • Piperidines / pharmacology
        • Pirenzepine / pharmacology
        • Receptors, Muscarinic / analysis
        • Receptors, Muscarinic / classification
        • Trachea / chemistry
        • Trachea / drug effects
        • Trachea / physiology

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        Citations

        This article has been cited 2 times.
        1. Abraham G, Kottke C, Ammer H, Dhein S, Ungemach FR. Segment-dependent expression of muscarinic acetylcholine receptors and G-protein coupling in the equine respiratory tract.. Vet Res Commun 2007 Feb;31(2):207-26.
          doi: 10.1007/s11259-006-3396-zpubmed: 17180451google scholar: lookup
        2. Törneke K, Ingvast-Larsson C, Boström A, Appelgren LE. Muscarinic receptors in equine airways.. Vet Res Commun 2002 Dec;26(8):637-50.
          doi: 10.1023/a:1020924921676pubmed: 12507038google scholar: lookup
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