Relaxation following contraction in tonically contracted smooth muscle from the bovine trachea.
Isometric tension was recorded from strips of bovine tracheal smooth muscle in which the tone had been artificially raised by agonist drugs such as histamine and carbachol. Application of exogenous acetylcholine produced a biphasic response consisting of an initial contraction followed by a more prolonged relaxation before tone was restored to normal. Atropine blocked both components of the biphasic response to exogenous acetylcholine. Tetrodotoxin blocked neither phase of the response to exogenous acetylcholine even though a similar biphasic response to electrical stimulation was severely disrupted. Application of exogenous substance P produced a biphasic response of similar magnitude and form to that produced by acetylcholine. Application of exogenous histamine (tone raised by carbachol) also produced a biphasic response although higher concentrations were required to produce a relaxation of equal magnitude to that produced by acetylcholine. It is concluded that the inhibitory component of the biphasic response to exogenous acetylcholine occurs as a non-specific sequel to contraction.
H M
HM
Clarke
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CT
Kirkpatrick
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002417:Cattle; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D018377:Neurotransmitter Agents / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000187:drug effects; D013373:Substance P / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects
D018377:Neurotransmitter Agents; D011976:Receptors, Muscarinic; D013373:Substance P; D013779:Tetrodotoxin; D001285:Atropine; D006632:Histamine; D000109:Acetylcholine