Electrical stimulation-induced alpha1- and alpha2-adrenoceptors-mediated contraction in isolated dog thoracic ducts.
The electrical stimulation-induced responses of isolated dog thoracic ducts were investigated using an organ bath technique. Electrical stimulation (0.7 ms in pulse width, 25 V in nominal voltage, 10 s in duration time, 1-32 Hz at frequency) produced frequency-related contractions in the lymphatic preparations. The contractions were abolished by pretreatment with tetrodotoxin (10(-7) M), guanethidine (10(-7), 10(-6) M), and bretylium (10(-7), 10(-6) M). Cocaine (10(-6) M) significantly potentiated the electrical stimulation-induced contractions. Phentolamine (10(-8)-10(-5) M), prazosin (10(-8)-10(-5) M), bunazosin (10(-6), 10(-5) M), yohimbine (10(-8)-10(-6) M) and rauwolscine (10(-8)-10(-6) M) also dose-dependently reduced the contractions. On the other hand, propranolol (10(-8)-10(-6) M), atropine (10(-6) M), hexamethonium (10(-6) M), aspirin (3 x 10(-5) M), N(omega)-nitro-L-arginine methyl ester (L-NAME) (3 x 10(-5) M) and L-NAME (3 x 10(-5) M) + L-arginine (10(-4) M) caused no significant effect on electrical stimulation-induced contractions. No significant difference in the electrical stimulation-induced responses was observed between the lymphatic preparations with and without an intact endothelium. The electrical stimulation caused only a small contraction with no relaxation in the thoracic duct preparation precontracted with 10(-8) M U46619. The small contraction was abolished by 10(-5) M phentolamine. These findings suggest that there exists alpha1- and alpha2-adrenoceptors-mediated excitatory innervation, but no NO-ergic inhibitory nerve fiber in dog thoracic ducts.
The 1st Department of Physiology, Shinshu University School of Medicine, Asahi, Matsumoto, Japan.
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Igarashi
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Ikomi
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Ohhashi
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D018674:Adrenergic Antagonists / Q000494:pharmacology; D000818:Animals; D004285:Dogs; D004558:Electric Stimulation; D004730:Endothelium, Vascular / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors; D011930:Reaction Time / Q000502:physiology; D011942:Receptors, Adrenergic, alpha; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*; D013897:Thoracic Duct / Q000187:drug effects / Q000502:physiology*
D018674:Adrenergic Antagonists; D004791:Enzyme Inhibitors; D011942:Receptors, Adrenergic, alpha; D018340:Receptors, Adrenergic, alpha-1; D009569:Nitric Oxide; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D019331:NG-Nitroarginine Methyl Ester