Bradykinin receptor inhibition affects the rod b-wave in the cat electroretinogram

In 10 anaesthetized cats, electroretinographic (ERG) measurements were carried out to further elucidate the involvement of bradykinin as a substrate component of the renin-angiotensin system in retinal neurotransmission. Reducing angiotensin II concentration by angiotensin-converting enzyme (ACE) inhibition increased sensitivity (0.5 log units) and gain (50%) of the rod b-wave amplitude. The b-wave implicit time was decreased only at high stimulus intensities (> 10(-2) cd/m). Blocking bradykinin receptors specifically decreased rod b-wave implicit time for all intensities, while its amplitude remained unaffected. Bradykinin effects were independent of alterations of angiotensin II activity. We therefore suggest that bradykinin influences inner retinal signal processing, hereby further supporting the hypothesis of a renin-angiotensin system involvement in retinal neurotransmission.