EFFECT OF CAPTOPRIL ON OCULAR IRRITATIVE RESPONSE TO TOPICAL NEUTRAL FORMALDEHYDE AND YAG-LASER CAPSULOTOMY IN THE RABBIT

Angiotensin converting enzyme (ACE) -inhibitors inhibit degradation of inflammatory mediators substance P (SP) and bradykinin, which may fur ther stimulate the synthesis of prostaglandins, The resulting increase in inflammatory mediators in tissues is suggested to be the reason fo r the dry cough, involving sensory C-fiber activation, among patients receiving ACE-inhibitor therapy. In the present study, the effect of a n ACE-inhibitor, captopril, on ocular irritative responses was studied in the rabbit. Intravenous captopril decreased markedly the blood pre ssure and the intraocular pressure (IOP) modestly. Topical neutral for maldehyde elicits an irritative response in the eye mediated through s ensory neuropeptides SP and calcitonin gene-related peptide (CGRP). Fo llowing topical neutral formaldehyde, the increase in IOP and breakdow n of the blood-aqueous barrier were inhibited by captopril, while mios is was not affected, Cyclic AMP (cAMP) content in the aqueous humour w as increased by captopril, and this increase was inhibited by indometh acin. Following YAG-laser anterior capsulotomy, captopril inhibited th e increase in IOP, breakdown of the blood-aqueous barrier and miosis. The present study demonstrates that use of short-term administration o f captopril prior to sensory nerve stimulation or YAG laser anterior c apsulotomy does not enhance the ocular responses to these stimuli in t he rabbit. In the present study, captopril inhibited these responses, at least partly by decreasing the blood pressure.