3H-norepinephrine release in caudal artery of spontaneously hypertensive and Wistar-Kyoto rats: effects of altered salt diets.

The potassium-induced release of 3H-norepinephrine (3H-NE) was examined in the rat caudal artery. A simple and reliable method was developed to examine stimulated neurotransmitter release from this highly innervated resistance vessel. The potassium-induced release of 3H-NE was dose- and calcium-dependent. Stimulated 3H-NE release was elevated in the spontaneously hypertensive (SHR) compared to age-matched Wistar-Kyoto (WKY) animals (p less than 0.05). However, in animals at 5-6 weeks of age, where the blood pressure was not different between the SHR and WKY, the stimulation-induced release of 3H-NE was also not significantly different. Low salt diets for 7 days significantly decreased the potassium-induced release of 3H-NE from both 10- to 11-week-old SHR and WKY animals. High salt diets did not significantly effect 3H-NE release, even though the high salt diets for 7 days significantly increased the blood pressure in the SHR. The results suggest that the caudal artery is a good model to study stimulation-induced transmitter release and that elevated 3H-NE release plays a role in the development of hypertension in the SHR. Low salt diets, which did not lower blood pressure, were shown to decrease 3H-NE release. High salt diets elevated the blood pressure in the SHR but had no significant effect on stimulated 3H-NE release.