Effects of Goniopora toxin on guinea-pig blood vessels

Summary Effects of a marine polypeptide, Goniopora toxin (GPT) (molecular weight 12,000), were examined in isolated blood vessels of guinea pigs. GPT, ranging from 10–100 nM, augmented the contractile response to electrical transmural stimulation in the thoracic aorta, portal vein, and mesenteric and femoral arteries. The effects were abolished by tetrodotoxin and bretylium, and were markedly attenuated by phentolamine. As GPT did not affect the resting tension, spontaneous rhythmicity or noradrenaline-induced contraction, the toxin appears to act on the neural elements in the vascular wall rather than on the smooth muscle. In the portal vein preloaded with³H-noradrenaline, GPT enhanced the³H-efflux in response to electrical transmural stimulation, yet had no effect on the spontaneous efflux. The increase in stimulation-evoked³H-efflux caused by GPT was more than 15 times larger than the increase seen with cocaine or phentolamine. Tetrodotoxin completely blocked the³H-efflux induced by electrical transmural stimulation. These data suggest that GPT acts on nerve components in guinea pig blood vessels and increases the release of noradrenaline evoked by electrical stimulation of the nerve fibers. These effects are probably associated with prolongation of the action potential duration and repetitive discharges in the adrenergic nerve fibers.This work was supported in part by Grant in Aid for Scientific Research from the Ministry of Education, Science and Culture, Japan (No. 44026), and by the Mitsubishi Foundation Research Grant for 1978