title: Adrenergic effects on the corneal and intraretinal direct-current electroretinogram and on the standing potential of albino rabbit eyes.
abstract: This study was undertaken to investigate further the responsiveness of the albino rabbit retinal pigment epithelium and the inner retina to adrenergic agents as reflected in changes of the direct-current electroretinogram and of the standing potential of the eye. After unilateral vitrectomy on albino rabbits, a continuous intraocular perfusion with a reference solution was established. The reference solution was then alternated with the test solution. The direct-current electroretinogram and the standing potential were recorded from both eyes with a scleral contact lens and a reference electrode connected to matched calomel half-cells. An in vivo experimental technique that allows intraocular perfusion of a test substance and simultaneous intraretinal microelectrode measurements was also used. The alpha-adrenergic agonist phenylephrine (0.04 microM, n = 8) produced a reversible increase in c-wave amplitude (48%, p < 0.001) and also a small increase in b-wave amplitude (12%, p < 0.002). There was no significant influence on the a-wave amplitude. The standing potential was elevated at 1694 +/- 362 microV (mean +/- SEM) (p < 0.002). The alpha 2-adrenergic agonist clonidine caused similar effects on the electroretinogram, although at a higher concentration (40 microM, n = 5), with an elevation of the c-wave (25%, p < 0.001) and a small b-wave increase (12% p < 0.002). No significant influence on the a-wave or on the standing potential was found. Intraretinal direct-current electroretinogram-recordings during intraocular perfusion with phenylephrine showed an increase in transepithelial potential (p < 0.004; n = 6), accompanied by a reduction of the slow PIII (p < 0.0035; n = 6). The c-wave increase resulting from alpha-adrenergic stimulation seems to be generated partly across the retinal pigment epithelium, with an increase in transepithelial potential, combined with a reduction of the slow PIII. The elevation of the b-wave amplitude, together with the influence on the slow PIII, suggests alpha-adrenergic effects also on the inner retina. The experimental technique used in this study with intraocular perfusion after vitrectomy and simultaneous intraretinal direct-current recordings seems to be a practicable method for studies of the influence of pharmacologic agents on the retina and the retinal pigment epithelium.
authors.affiliation: Department of Ophthalmology, Linköping University, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Jarkman
authors.forename: R
authors.initials: R
authors.lastname: Bragadóttir
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D003000:Clonidine / Q000494:pharmacology*; D003315:Cornea / Q000187:drug effects / Q000502:physiology*; D004596:Electroretinography / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D008839:Microelectrodes; D010477:Perfusion; D010656:Phenylephrine / Q000494:pharmacology*; D011817:Rabbits; D012160:Retina / Q000187:drug effects / Q000502:physiology*; D014821:Vitrectomy
chemical_list: D000316:Adrenergic alpha-Agonists; D010656:Phenylephrine; D003000:Clonidine