Remodeled structure and reduced contractile responsiveness of ocular ciliary artery in spontaneously hypertensive rats

AIM: To investigate the alterations in both structure and contractile responsiveness of ocular ciliary artery(OCA) in spontaneously hypertensive rat(SHR).METHODS: In this experiment, 20-week-old male SHR and Wistar Kyoto rat(WKY) were studied. The heart rate(HR), the blood pressure(BP; the systolic BP and the diastolic BP) of rats with an electronic sphygmomanometer were measured. Vascular morphometry and isometric tension measurement were used to investigate the alterations in structure and contractility of OCA.RESULTS: A general narrowing of OCAs was observed in SHR compared to the control WYK. In SHR, the media of OCAs were thicker, the luminal diameters were smaller, and the media-to-lumen ratios were higher when compared with WKY(P<0.05). The contractions of OCAs evoked by norepinephrine were smaller in SHR compared to control(P<0.05). Then, OCAs were pretreated with iberiotoxin, L-NAME, or indomethacin 30 min before norepinephrineinduced contraction. Iberiotoxin(0.1 μmol/L) has not changed the norepinephrine-induced contractions in OCAs from both groups. However, L-NAME(100 μmol/L) increased the vasoconstrictions, the increased extents were similar in SHR and WKY(P>0.05). Indomethacin(10 μmol/L) decreased the contractions induced by norepinephrine in OCAs from WKY(P<0.05), but did not change those contractions in vessels from SHR(P>0.05).CONCLUSION: Our results demonstrate that the structure and function of OCAs are altered in hypertension. OCAs from SHR are remodeled with decreased lumen diameter and increased media-to-lumen ratio. Moreover, the contractile responsiveness of OCAs from SHR is diminished due to the disruption of vasoconstrictive effect of prostaglandins.

Effects of brinzolamide on rabbit ocular blood flow in vivo and ex vivo

AIM：To investigate if significant improvement of optic disc blood flow（ODBF） occurs after instillation of brinzolamide onto rabbit eyes.METHODS：Testing of bilateral intraocular pressure（IOP） and left ODBF in 10 male rabbits took place every 3 h over a 24 h period.Brinzolamide（1% ophthalmic solution,two drops at 9：00 and 21：00） was administered to the left eye.ODBF,assessed using laser speckle flowgraphy,was determined as the mean blur rate（MBR）.Furthermore,the effect of brinzolamide on isolated rabbit ciliary arteries using isometric tension recording system was performed.RESULTS：After brinzolamide instillation,IOP was significantly decreased in the left eye.MBR-vessel was greater at 18：00 and 21：00（P〈0.05） than in the controls.MBRtissue and MBR-average were greater at 18：00（P〈0.05） than in the controls.For isolated arteries pre-contracted with a high-K solution,brinzolamide induced concentration-dependent relaxation,reaching 46.1%±9%（n=21） at 1 mmol/L.In Ca^2＋-free solutions,incubation with brinzolamide suppressed 1 μmol/L histamine-induced contractions（P〈0.05）.CONCLUSION：Brinzolamide decreases IOP and increases ocular blood flow.The direct vasodilatory effect of brizolamide is mediated by suppression of Ca^2＋ release from intracellular calcium stores.