Biologia, Bratislava 54/Suppl. 6: 139-144, 1999.
ISSN 0006-3088 (Biologia). ISSN 1335-6399 (Biologia. Section Cellular and Molecular Biology).
The amplifying effect of serotonin on responses of isolated arteries of rabbits to adrenergic stimuli.
Institute of Normal and Pathological Physiology, Slovak Academy of Sciences, Sienkiewiczova 1, SK-81371 Bratislava, Slovakia; tel.: ++421 7 326271, 326336, fax: ++421 7 368516, e-mail: firstname.lastname@example.org
Received: December 16, 1998 / Accepted: October 5, 1999
Experiments were designed to determine the possible involvement of calcium mobilization on the amplifying effect of 5-hydroxytryptamine (5-HT) on contractions induced in isolated arteries by transmural nerve stimulation and exogenous noradrenaline. Ring segments of the pulmonary and mesenteric arteries of rabbits were studied under isometric conditions in organ baths filled with a Krebs solution. 5-HT, at threshold concentration (10-8 mol/L), amplified the contractile responses evoked by nerve stimulation and noradrenaline in both types of arteries. The magnitude of amplification was markedly higher in mesenteric than in pulmonary artery segment. The calcium antagonist diltiazem reduced noradrenaline-induced contractions. 5-HT did not affect either the diltiazem-resistant component of noradrenaline-contraction or the residual noradrenaline-contraction in Ca2+-free solution. These results support an assumption that the amplifying effect of 5-HT is exerted on the component of the noradrenaline-contraction that is dependent on the entry of extracellular calcium. The process of amplification of adrenergic contractions appears to be due to an activation of 5-HT2 subtype receptors that are coupled to an increase in Ca2+ influx into the vascular smooth muscle cells.
Key words: pulmonary and mesenteric arteries of rabbits, serotonin, noradrenaline, amplifying effect, Ca2+ mobilization.