Abstract

Vascular smooth muscle cells derived from bovine basilar artery by the explant method were grown in culture. In the presence of 1 microM forskolin and the phosphodiesterase inhibitor rolipram, 5-hydroxytryptamine (5-HT) agonists inhibited by 90 to 100% the accumulation of intracellular cyclic AMP (cAMP) with a rank order of potency 5-carboxamidotryptamine (5-CT) > or = 5-HT > 5-benzyloxytryptamine = sumatriptan > RU24969 [5-methoxy-3(1,2,3,6-tetrahydro-4-pyridinyl)-1H indole succinate] > (+/-)-8-hydroxydipropylaminotetralin. In suspensions of cells loaded with the calcium-sensitive probe fura-2, 5-CT and 5-HT caused a biphasic increase in the concentration of intracellular free calcium ([Ca++]i) that consisted of both transient and sustained phases. The transient phase was reduced and the sustained phase abolished in the absence of extracellular calcium. The EC50 for 5-CT-induced increase in [Ca++]i (6 nM) was similar to that for inhibition of cAMP accumulation (1.3 nM). Both the inhibition of cAMP accumulation and increase in [Ca++]i were inhibited by the antagonist methiothepin (pA2 = 8.9), but not by the antagonists ketanserin, spiperone and pindolol. Both the inhibition of cAMP accumulation and increase in [Ca++]i were attenuated by greater than 85% in cells that were pretreated with pertussis toxin. PI turnover was not stimulated by 5-CT. The rank order of agonist potency, as well as the antagonist sensitivity, indicates responses mediated by one or more 5-HT1-like-type receptors.(ABSTRACT TRUNCATED AT 250 WORDS)