Expression of mRNA for the serotonin 5-hydroxytryptamine1D beta receptor subtype in human and bovine cerebral...

Serotonin [5-hydroxytryptamine (5-HT)] has been implicated in the pathophysiology of migraine, and the clinical efficacy of the 5-HT1B/5-HT1D receptor agonist sumatriptan points to neural and/or vascular 5-HT1D receptors as relevant targets in migraine therapy. We characterized the human and/or bovine 5-HT1D receptor subtype in cerebral blood vessels pharmacologically by correlation analysis and molecularly by Northern blot hybridization of cerebrovascular RNA extracts. Pharmacological analysis showed that sumatriptan was less potent than 5-HT in inducing contraction in freshly isolated human cerebral arteries and revealed an overall pharmacological profile positively and significantly correlated with that published for the 5-HT1D alpha (r = 0.746, p = 0.021) and 5-HT1D beta (r = 0.942, p = 0.0001) cloned human receptor subtypes. These results are suggestive of a contractile 5-HT1D beta receptor subtype but are not conclusive. However, Northern blots revealed the presence of mRNA transcripts for the 5-HT1D beta subtype, but not the 5-HT1D alpha subtype, in bovine (approximately 2.2 kilobases) and human (approximately 4.5 kilobases) cerebral blood vessels. Expression of either subtype could not be detected in intraparenchymal microvessels or capillaries isolated from bovine or human cerebral cortex. These results clearly indicate that the beneficial effect of sumatriptan in migraine attack, if vascularly related, is mediated by contractile 5-HT1D beta receptors most likely located on cerebral blood vessels at the surface of the brain. This study points to the 5-HT1D beta receptor subtype as the putative cerebrovascular target for migraine therapeutic agents.