Antinociceptive action of bradykinin and related kinins of larger molecular weights by the intraventricular route

Abstract

1 It was shown previously that bradykinin (Bk) when given intraventricularly increases the threshold of electrical stimulation of dental pulp in the rabbit. 2 Bradykinin derivatives with increasing molecular weights (lysyl-Bk (L-Bk), methionyl-lysyl-Bk (ML-Bk) and glycyl-arginyl-methionyl-lysyl-Bk (GAML-Bk)) were found to produce effects of decreasing intensity on the threshold of electrical stimulation according to the following scale: Bk (1·00)>L-Bk (0·28)>ML-Bk (0·060)>GAML-Bk (0·047). 3 The four peptides had similar relative activities on the guinea-pig ileum but an inverse relationship in their effects on vascular permeability and rat blood pressure. 4 The discrimination index, increase in vascular permeability/antinociceptive effect rose to values of the order of 170 to 550, taking Bk as the reference peptide (potency = 1·00). 5 We conclude that the increase in threshold of electrical stimulation could not be due to an increase in vascular permeability or decrease of blood pressure.