Ketanserin and vascular contractions in response to cooling.

Rings of tibial arteries of the rabbit were suspended for isometric tension recording in organ chambers filled with oxygenated physiological salt solution. 5-Hydroxytryptamine caused contractions which were enhanced by cooling from 37 to 29 degrees C. Both the contractions induced by 5-hydroxytryptamine and their augmentation by cooling were inhibited by similar concentrations of the serotonergic 5-HT2 antagonist ketanserin. These experiments demonstrate that cooling augments the responsiveness of peripheral arteries to 5-hydroxytryptamine and that the augmentation is mediated by 5-HT2 serotonergic receptors.