APStracts 2:0059H, 1995.

5-hydroxytryptamine-induced nitric oxide-dependent relaxation in isolated strips of monkey popliteal lymph nodes. Mizuno, Risuke, and Toshio Ohhashi. The 1st Department of Physiology, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390, Japan

APStracts 2:0059H, 1995.

5-hydroxytryptamine (5-HT, 0.01 to 100 [mu]M) and 5 -carboxamidotryptamine (5-CT, 0.001 to 10 [mu]M) produced dose-related relaxations in strips cut from monkey popliteal lymph nodes pre -contracted with a perfusion of Krebs-bicarbonate solution containing 80 mM KCl. These 5-HT agonists caused no significant effect on the basal tone of the lymph node strips. The 5-HT-induced relaxation is completely antagonized by pretreatment with a selective 5-HT1-like receptor antagonist, methiothepin (0.01 to 0.1 [mu]M). Schild plot analysis showed that the pA2 value and slope of methiothepin against 5-HT were 8.80+/-0.11 and 0.99+/-0.07 (n=6), respectively. Pretreatment with methysergide (0.01 to 0.1 [mu]M) significantly attenuated the 5-HT-induced relaxation of the strips. On the other hand, treatment with ketanserin (0.01 to 0.1 [mu]M) and ICS 205-930 (0.01 to 0.1 [mu]M) caused no significant effect on the 5-HT-or the 5-CT-induced relaxation. The 5-HT-induced relaxation was significantly reduced by 10 [mu]M NG-monomethyl-L-arginine (L-NMMA), which was reversed by 1 mM L-arginine. The relaxation in the lymph node strips was also significantly reduced by treatment with 10 [mu]M methylene blue, but not with 30 [mu]M aspirin. These results suggest that 5-HT1-like receptors exist in the monkey popliteal lymph nodes. Stimulation of these receptors produces an endogenous nitric oxide -dependent relaxation in lymph node smooth muscle through an activation of cytosolic guanylate cyclase in the cells.

Received 3 October 1994; accepted in final form 30 December 1994.
APS Manuscript Number H888-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on  7 March 1995.