Vascular reactivities of simian ophthalmic and ciliary arteries

Abstract

Vascular reactivities to vasoactive substances were compared with ophthalmic and ciliary arteries (OAs and CAs) of Japanese monkeys. These two kind of arteries were perfused with Tyrode solution under a constant flow rate at 37°C, respectively. Each drug solution was given by a microinjector into the endothelial side of the artery through a cannulated tubing, and responses were obtained as changes in perfusion pressure. Results were as follows: 1) Norepinephrine induced vasoconstriction in a dose-related manner in both arteries. The threshold dose was approximately 0.01 μg in OAs and 0.1 μg in CAs. The maximum value was approximately 45 mmHg in OAs and 20 mmHg in CAs. 2) Phenylephrine induced vasoconstriction in almost the same grade in both arteries. 3) Xylazine caused no significant change in perfusion pressure in both arteries. 4) Tyramine showed only small vasoconstrictor responses in both arteries. 5) 5-HT induced vasoconstriction in a dose-related manner in both arteries. The threshold dose was 0.001 μg in CAs and 0.003 μg in OAs, which indicated the smallest threshold dose in examined substances. However, the maximum increase in perfusion pressure was about 30 mmHg in OAs and 20 mmHgin CAs even at large doses. 6) PGF2 α induced a moderate increase in perfusion pressure, and the response in CAs was significantly greater than that in OAs. 7) KC1 induced dose-dependent vasoconstriction. In CAs, the constriction induced by KC1 was slightly greater than that in OAs but not significant. Prom these results, it is considered that 1) both arteries may have few postjunctional alpha-2 adrenoceptors, 2) both areas have only small tyramine-sensitive catecholamine stores, and 3) in OAs norepinephrine may have an important role in regulating vasoreactivity. In CAs, PGs may be important.