5-HYDROXYTRYPTAMINE(1)-LIKE RECEPTORS LINKED TO INCREASES IN INTRACELLULAR CALCIUM-CONCENTRATION AND INHIBITION OF CYCLIC-AMP ACCUMULATION IN CULTURED VASCULAR SMOOTH-MUSCLE CELLS DERIVED FROM BOVINE BASILAR ARTERY

Vascular smooth muscle cells derived from bovine basilar artery by the explant method were grown in culture. In the presence of 1 muM forsko lin and the phosphodiesterase inhibitor rolipram, 5-hydroxytryptamine (5-HT) agonists inhibited by 90 to 1 00% the accumulation of intracell ular cyclic AMP (cAMP) with a rank order of potency 5-carboxamidotrypt amine (5-CT) greater-than-or-equal-to 5-HT > 5-benzyloxytryptamine = s umatriptan > RU24969 [5-methoxy-3(1,2,3,6-tetrahydro-4-pyridinyl)-1H i ndole succinate] > (+/-)-8-hydroxydipropylaminotetralin. In suspension s of cells loaded with the calcium-sensitive probe fura-2, 5-CT and 5- HT caused a biphasic increase in the concentration of intracellular fr ee calcium ([Ca++]i) that consisted of both transient and sustained ph ases. The transient phase was reduced and the sustained phase abolishe d in the absence of extracellular calcium. The EC50 for 5-CT-induced i ncrease in [Ca++]i (6 nM) was similar to that for inhibition of cAMP a ccumulation (1.3 nM). Both the inhibition of cAMP accumulation and inc rease in [Ca++]i were inhibited by the antagonist methiothepin (pA2 = 8.9), but not by the antagonists ketanserin, spiperone and pindolol. B oth the inhibition of cAMP accumulation and increase in [Ca++]i were a ttenuated by greater than 85% in cells that were pretreated with pertu ssis toxin. PI turnover was not stimulated by 5-CT. The rank order of agonist potency, as well as the antagonist sensitivity, indicates resp onses mediated by one or more 5-HT1-like-type receptors. Bovine basila r artery cells that naturally express 5-HT1-like receptors may serve a s a useful model for the study of 5-HT1-like receptor-mediated signal transduction mechanisms in vascular smooth muscle.