Reduction of cephalic arteriovenous shunting by ergotamine is not mediated by 5‐HT 1 ‐like or 5‐HT 2 receptors

• Published in: British journal of pharmacology Vol. 97; no. 2; pp. 383 - 390
• Main Authors: Bom, Anton H., Heiligers, Jan P.C., Saxena, Pramod R., Verdouw, Pieter D.
• Format: Journal Article
• Language: English
• Published: 01-06-1989
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1111/j.1476-5381.1989.tb11965.x

The potent, antimigraine drug ergotamine has affinity for both 5‐HT
1
and 5‐HT
2
binding sites and constricts arteriovenous anastomoses. Since 5‐HT also constricts arteriovenous anastomoses (mainly via 5‐HT
1
‐like receptors), this study investigates the involvement of 5‐HT receptors in the ergotamine‐induced reduction of arteriovenous shunting in the carotid circulation of the cat and pig.
In the cat, ergotamine (3, 10 and 30 μg kg
−1
, i.v.) reduced carotid blood flow, predominantly by a reduction in arteriovenous anastomotic blood flow. Pretreatment with ketanserin (0.5 mg kg
−1
, i.v.) or methiothepin (1 mg kg
−1
, i.v.) did not antagonize the effects of ergotamine.
In the pig, ergotamine (2.5, 5, 10 and 20 μg kg
−1
, i.v.) also reduced carotid blood flow and arteriovenous shunting, which was not affected by pretreatment with methiothepin (1 mg kg
−1
, i.v.).
These results suggest that the reduction by ergotamine in the shunting of carotid arterial blood via cephalic arteriovenous anastomoses is not mediated by 5‐HT
1
‐like or 5‐HT
2
receptors.