NEUROKININ-INDUCED CHANGES IN PIAL ARTERY DIAMETER IN THE ANESTHETIZED GUINEA-PIG

1 The effects of selective neurokinin agents on pial artery diameter, measured with an on-line image analyser, have been studied in anaesthetized guinea-pigs in order to characterize the neurokinin receptors present on pial arteries. 2 Perivascular injection of either substance P (0.01-1 muM) or the selective NK1 receptor agonists, substance P methyl ester (SPOMe, 0.01-1 muM) and GR73632 (0.1 muM), increased pial artery diameter. 3 In contrast, the selective NK2 receptor agonist, GR64349 (1 muM), produced a small vasoconstriction while the NK3 receptor-selective agonist, senktide (1 muM) was inactive. 4 Co-administration of GR82334 (1 muM), a selective NK1 receptor antagonist, inhibited the vasodilatation produced by SPOMe (0.1 muM) but not that caused by calcitonin gene-related peptide (CGRP, 0.01 muM). 5 The results are consistent with an involvement of NK1 receptors in the neurokinin-induced increase in guinea-pig pial artery diameter.