Electrical stimulation-induced alpha1- and alpha2-adrenoceptors-mediated contractions of isolated canine lymph nodes.
The contractile effects of alpha-adrenoceptor agonists and field electrical stimulation were investigated pharmacologically in canine isolated tracheobronchial lymph nodes. Addition of noradrenaline (NA), phenylephrine (Phe) and UK14,304 caused dose-related contractions of the isolated lymph nodes. Pretreatment with prazosin (3 x 10(-9), 3 x 10(-8) and 3 x 10(-7) M) shifted the concentration-response curve for phenylephrine to the right, whereas yohimbine (3 x 10(-7) M) did not affect the contractile responses to phenylephrine. On the other hand, the concentration-response curve for UK 14,304 shifted to the right by treatment with yohimbine (3 x 10(-9), 3 x 10(-8) and 3 x 10(-7) M) but not by prazosin (3 x 10(-7) M). Field electrical stimulation (25 V, 0.7 ms, 16 Hz) produced contractile responses of the lymph nodes. The electrical stimulation-induced contractions were completely reduced by pretreatment with tetrodotoxin (TTX) (3 x 10(-7) M) or bretylium (10(-6) M). Furthermore, phentolamine (10(-8), 10(-7) and 10(-6) M), prazosin (3 x 10(-9) and 3 x 10(-8) M) and yohimbine (3 x 10(-8) and 3 x 10(-7) M) significantly reduced the electrical stimulation-induced contractions in the preparations. The present findings suggest that there are both alpha1- and alpha2-adrenoceptors located on the smooth muscle cells in canine tracheobronchial lymph nodes, and that the adrenoceptors-mediated excitatory mechanisms of adrenergic innervation exist in the lymph nodes.
Ikomi
Fumitaka
F
The 1st Department of Physiology, Shinshu University School of Medicine, Matsumoto, Japan. fikomi@sch.md.shinshu-u.ac.jp
Kousai
Akira
A
Ono
Nobuyuki
N
Ohhashi
Toshio
T
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001980:Bronchi; D004285:Dogs; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D008198:Lymph Nodes / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000166:cytology / Q000502:physiology*; D010646:Phentolamine / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D013268:Stimulation, Chemical; D014132:Trachea; D014439:Tyramine / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D011942:Receptors, Adrenergic, alpha; D014439:Tyramine; D010646:Phentolamine