Objective. To examine whether retinal electrophysiology is a useful surrogate marker of drug penetrance into the central nervous\nsystem (CNS). Materials and Methods. Brain and retinal electrophysiology were assessed with full-field visually evoked potentials\nand electroretinograms in conscious and anaesthetised rats following systemic or local administrations of centrally penetrant\n(muscimol) or nonpenetrant (isoguvacine) compounds. Results. Local injections into the eye/brain bypassed the blood neural\nbarriers and produced changes in retinal/brain responses for both drugs. In conscious animals, systemic administration of\nmuscimol resulted in retinal and brain biopotential changes, whereas systemic delivery of isoguvacine did not. General anaesthesia\nconfounded these outcomes. Conclusions. Retinal electrophysiology, when recorded in conscious animals, shows promise as a\nviable biomarker of drug penetration into the CNS. In contrast, when conducted under anaesthetised conditions confounds can be\ninduced in both cortical and retinal electrophysiological recordings.
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