Effects of inhibition of neuronal nitric oxide synthase on basal retinal blood flow regulation

Shanti R. Tummala, Sanja Benac, Harry Tran, Anand Vankawala, Astrid Zayas-Santiago, Alyssa Appel, Jennifer J. Kang Derwent

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12 Scopus citations

Abstract

Nitric oxide (NO) has been observed to regulate blood flow under basal and stimulated conditions in the retina. Recent evidence suggests that NO produced by neuronal nitric oxide synthase (nNOS) may regulate blood flow in addition to that produced by endothelial nitric oxide synthase (eNOS). The objective of the current study was to investigate the contribution of NO produced by nNOS in the regulation of basal retinal blood flow. A non-specific NOS inhibitor N (G)-nitro-l-arginine methyl ester (l-NAME) and the specific nNOS inhibitors 1-(2-trifluoromethylphenyl) imidazole (TRIM) and (4S)-N-(4-amino-5 [aminoethyl] aminopentyl)-N-nitroguanidine (AAAN) were injected into the vitreous (intravitreal) of Long-Evans rats. Vessel diameters, velocities and volumetric blood flow rates (VBF) in the retinal circulation were determined prior to and in 30-min intervals for 4-4.5 h after injection. In addition, the basal amount of nNOS in the rat retina was quantified using a specific enzyme linked immunoassay (ELISA). Treatment with l-NAME and TRIM significantly decreased diameters and VBF. Compared with saline, treatment with l-NAME and TRIM produced a significant (p < 0.001) decrease of ∼12-17% in vessel diameters. Treatment with AAAN significantly decreased vessel diameters and venous VBF. Compared with saline AAAN produced a significant decrease of ∼7% in arterial (p < 0.001) and 5% in venous (p = 0.011) diameters, respectively. The amount of nNOS in the rat retina was 0.17 ± 0.0147 pmol mg-1 of dry retina. The results suggest that though inhibition of nNOS decreases basal diameters, constant VBF is maintained in the retinal circulation.

Original languageEnglish
Pages (from-to)801-809
Number of pages9
JournalExperimental Eye Research
Volume89
Issue number5
DOIs
StatePublished - Nov 2009

Keywords

  • basal retinal blood flow
  • neuronal nitric oxide synthase
  • nitric oxide

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