Neuromodulatory effects of the renin-angiotensin system on the cat electroretinogram.
OBJECTIVE
Angiotensin-converting-enzyme (ACE) catalyses the formation of angiotensin II (ANGII), which presumably acts as a central neurotransmitter/modulator. ANGII-related effects have also been observed in the retina. Present in vivo experiments were designed to investigate further ANGII-related effects on retinal neuromodulation.


METHODS
In 12 anesthetized cats, electroretinographic measurements were carried out in the dark-adapted state using corneal contact lens electrodes and a Ganzfeld stimulator. Quinapril was used to inhibit ACE.


RESULTS
Reducing ANGII-concentration increased sensitivity (0.5 log units) and gain (50%) of the rod b-wave amplitude. The b-wave implicit time was stimulus dependent, shortening at high intensities. The scotopic threshold response and the oscillatory potentials were also influenced by ACE inhibition. However, a-wave and 30 Hz flicker remained unaffected. Effects of Quinapril on ERG-amplitudes were reversed by subsequent ANGII administration, except for the implicit time of the b-wave and scotopic threshold response.


CONCLUSIONS
Although these results are accompanied by alterations in systemic blood pressure, several findings support the evidence that the renin-angiotensin system might have a neurophysiologic effect on retinal neurons outside the vascular system. These results are in accordance with immunohistochemical data found by others that point to angiotensinergic cell involvement and thereby further support the concept of angiotensinergic processes in the inner retina from a functional point of view.
Jacobi
P C
PC
Department of Pathophysiology of Vision and Neuro-Ophthalmology, University Eye Hospital Tuebingen, Germany.
Osswald
H
H
Jurklies
B
B
Zrenner
E
E
D000804:Angiotensin II / Q000494:pharmacology*; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure; D002415:Cats; D003623:Dark Adaptation; D004078:Dihydralazine / Q000494:pharmacology; D004596:Electroretinography / Q000187:drug effects; D005260:Female; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D010775:Photic Stimulation; D000077583:Quinapril; D012084:Renin-Angiotensin System / Q000502:physiology*; D012160:Retina / Q000502:physiology*; D044005:Tetrahydroisoquinolines
D000806:Angiotensin-Converting Enzyme Inhibitors; D007546:Isoquinolines; D044005:Tetrahydroisoquinolines; D000804:Angiotensin II; D004078:Dihydralazine; D000077583:Quinapril