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Toke Bek, Kim Holmgaard; The Relaxing Effect Of Gaba On Porcine Retinal Arterioles In Vitro Depends On The Perivascular Retinal Tissue And Is Mediated By GabaC Receptors. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6042.
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© ARVO (1962-2015); The Authors (2016-present)
The functional integration of of visual input in the retina depends on inhibitory signalling which is mediated by several neurotransmitters including γ-amino butyric acid (GABA). Recent studies suggest that GABA may also be involved in the regulation of retinal vascular tone, but the mechanisms underlying this effect are presently unknown. Therefore, the purpose of the present study was to investigate the contribution of different GABA receptors in and around retinal arterioles to the regulation of retinal arteriolar tone.
Porcine retinal arterioles with preserved perivascular retinal tissue were mounted in a wire myograph. After pre-contraction with 10-6 M of the tromboxan analogue U46619, the relaxing effect of GABA and agonists to individual GABA receptors in the presence or not of specific inhibitors of these agonists, were examined. The experiments were repeated after removal of the perivascular retinal tissue
GABA induced a significant dilatation of retinal arterioles at concentrations higher than 10-5 M, an effect that depended on the presence of perivascular retinal tissue. This vasodilating effect disappeared after blocking with the GABAC receptor antagonist TPMPA, but not after blocking with the GABAB receptor antagonist CGP55845 or the GABAA receptor antagonist bicuculline. The GABAA receptor agonist isoguvacin and the GABAB receptor agonist baclofen had no effect on retinal vascular tone.
GABA induced dilatation of porcine retinal arterioles in vitro depends on the perivascular retinal tissue and is mediated by the GABAC receptor.
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