5‐Hydroxytryptamine receptor characterizations of human cerebral, middle meningeal and temporal arteries: regional differences

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Abstract
We have studied the regional distribution of 5‐hydroxytryptamine (5‐HT) receptor subtypes in fresh circular segments of human cerebral, middle meningeal, and temporal arteries. Vasomotor responses induced by a series of 5‐HT agonists and antagonists with some degree of selectivity were studied by using a sensitivein vitrosystem.Nine 5‐HT agonists were examined for contractile effects on the arteries. In cerebral and meningeal arteries 5‐carboxamidotryptamine (5‐CT) was more potent than 5‐HT. The opposite order of potency (5‐HT‐5‐CT) was found in temporal arteries. In the cerebral arteries 5‐methoxytryptamin (5‐MeOHT) was more potent than sumatriptan while sumatriptan was more potent than 5‐MeOHT in meningeal and temporal arteries.The 5‐HT1, receptor antagonist, methiothepin, competitively antagonized 5‐CT‐induced contractions in cerebral arteries, with aPA2, value of 9.05. 5‐HT‐induced contractions were competitively antagonized by ketanserin (5‐HT2) in the temporal arteriesPA2, value of 9.06). Methiothepin and ketanserin had non‐competitive antagonistic effects in the middle meningeal arteries. The 5‐HT3, selective antagonist ondansetron did not cause any shift of the contractions induced by 2‐methyl‐5‐HT in the temporal, cerebral and middle meningeal arteries.These results suggest that the cerebral arteries mainly contain 5‐HTid., or 5‐HT1,‐like receptors, and the temporal artery 5‐HT2, receptors; the data further indicate the presence of both receptor subtypes in the middle meningeal artery.

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