title: Effect of various neurotransmitters and electrical field stimulation on smooth muscle preparations from the esophagus of horses.
abstract: The effects of various neurotransmitters and electrical field stimulation on muscle strips from the distal equine esophagus were studied. Acetylcholine (ACH) caused concentration dependent (1.1-55 x 10(-6) mol/l) contractions of the longitudinal and circular muscle strips from the distal esophagus as well as from the lower esophageal sphincter (LES). Atropine (10(-5) mol/l) blocked these contractions. Noradrenaline (NA) induced concentration related (1.1-55 x 10(-6) mol/l) contractions of the muscle strips from the LES. This excitatory effect of noradrenaline was antagonized by the alpha 1-receptor antagonist prazosin. Tetrodotoxin (5 x 10(-6) mol/l) did not affect the contractile response of the muscle strips to noradrenaline (55 x 10(-6) mol/l). Noradrenaline (1.1-55 x 10(-6) mol/l) had no excitatory effect on the circular and the longitudinal muscle strips from the esophagus. Furthermore, noradrenaline induced a concentration dependent (1.1-55 x 10(-6) mol/l) relaxation of the longitudinal muscle strips from the esophagus. The relaxing effect of NA was antagonized by the beta-receptor antagonist propranolol (10(-5) mol/l). Histamine (10(-7)-10(-6) mol/l) elicited a contraction in 4 out of 18 muscle preparations from the LES. The histamine induced contractions were partly antagonized by the H1-receptor antagonist clemastine (10(-4) mol/l) and fully abolished by the H2-receptor antagonist clemastine (10(-4) mol/l). Electrical field stimulation (EFS, 5 Hz, 2 ms; 500 mA; 10 Hz, 2 ms; 500 mA) produced tetrodotoxin sensitive contractions in all three types of muscle strips. Atropine (10(-5) mol/l) fully suppressed these contractions in most preparations.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Institute of Veterinary Physiology, University of Zürich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Denac
authors.forename: P
authors.initials: P
authors.lastname: Bebié
authors.forename: E
authors.initials: E
authors.lastname: Scharrer
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D004947:Esophagus; D005260:Female; D006736:Horses / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000494:pharmacology*
chemical_list: D018377:Neurotransmitter Agents