Agonistic properties of alniditan, sumatriptan and dihydroergotamine on human 5-HT(1B) and 5-HT(1D) receptors expressed in various mammalian cell lines

Abstract

1. Alniditan, a novel migraine abortive agent, is a potent 5-HT(1B)/5-HT(1D) receptor agonist of nM affinity. We compared the agonistic properties of alniditan, sumatriptan and dihydroergotamine on the cloned human 5-HT(1B) receptor expressed at 200 fmol mg-1 protein (B(max)) in non-induced L929sA cells, at 740 fmol mg-1 protein in HEK 293 and at 2300 fmol mg-1 protein in mIFNβ-induced L929sA cells, and on the human cloned 5-HT(1D) receptor expressed in C6 glioma cells (B(max)) 780 fmol mg-1 protein). 2. Sodium butyrate treatment increased the expression level of human (h)5-HT(1B) receptors in HEK 293 cells and h5-HT(1D) receptors in C6 glioma cells approximately 3 fold, the binding affinities of [3H]-5-HT and [3H]-alniditan were unaffected. 3. Agonistic properties were evaluated based on inhibition of cyclic AMP accumulation in the cells after stimulation of adenylyl cyclase by forskolin or isoproterenol. Alniditan, sumatriptan and dihydroergotamine were full agonists at the h5-HT(1B) receptor (IC50 values were 1.7, 20 and 2 nM, respectively in HEK 293 cells) and h5-HT(1D) receptors (IC50 values of 1.3, 2.6 and 2.2 nM, respectively). At the h5-HT(1B) receptor the agonist potency of the compounds slightly increased with higher receptor density. The opposite was seen for antagonists (ocaperidone, risperidone and ritanserin). 4. This comparative study demonstrated that alniditan was 10 times more potent than sumatriptan at the h5-HT(1B) receptor, and twice as potent at the h5-HT(1D) receptor. Dihydroergotamine was more potent an agonist at the h5-HT(1B) receptor when expressed at high and low level in L929sA cells (but not in HEK 293 cells), and was less potent at the h5-HT(1D) receptor.