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K.H. Jensen, A. Hessellund, C. Aalkjaer, J.D. C. Lambert, T. Bek; Blocking of the Glutamate NMDA Receptor and Prostaglandin Synthesis Eliminates the Vasodilation Induced by Perivascular Tissue in Porcine Retinal Arterioles in vitro . Invest. Ophthalmol. Vis. Sci. 2006;47(13):477.
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Retinal hyperperfusion due to disturbances in the tone regulation of retinal arterioles is involved in the pathophysiology of a variety of vision threatening retinal diseases. Previous studies of the influence of perivascular tissue on retinal vascular tone have been hampered by the release of a relaxing factor from the retinal tissue that renders the retinal arteriole insensitive to vasoconstrictors. Evidence from cerebral arterioles suggests that the perivascular tissue can inhibit vascular tone through the release of neurotransmitters and prostaglandins.
The contractility of porcine retinal arterioles to the thromboxane analogue U46619 was studied with retinal tissue preserved around the arteriole and after this tissue had been removed. The influence of the glutamate antagonist DL–APV (n=12), the GABA antagonist Picrotoxin (n=8), and the COX antagonist Ibuprofen (n=7) were studied.
The presence of perivascular tissue reduced the contractility of the vessels significantly (p<0.05). This reduction in contractility was unchanged by pre–incubation with the GABA–antagonist Picrotoxin (p<0.05), but was eliminated by pre–incubation with the glutamate antagonist DL–APV. The effect of DL–APV could be reverted spontaneously after a 1 h. incubation period (p<0.05). The prostaglandin synthesis inhibitor Ibuprofen eliminated the inhibitory effect of retinal tissue on vasoconstriction (p<0.05).
In studies of tone regulation of retinal vessels it is necessary to block factors that inhibit vascular contraction that are released from perivascular retinal tissue. These factors may include glutamate and the inhibiting effect on vasoconstriction may be mediated through prostaglandins.
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