Time change of rabbit aqueous flow under influence of adrenergic drugs

The changes in the aqueous flow rate with time under action of acetazolamide, a selective alpha 1 agonist, phenylephrine, selective beta 2 agonist, salbutamol, and beta antagonist, timolol, were studied by the pre-invasive method of Johnson and Maurice in the normal rabbit. After intravenous injection of 50 mg kg-1 of acetazolamide, the experimental to control ratio of the apparent flow rate significantly decreased to 71 +/- 2% at 2 hr and 53 +/- 2% at 4 hr (mean +/- S.E.(M.), n = 7). After a single instillation of 5% L-phenylephrine, it showed two phase changes; it significantly increased to 121 +/- 5% at 1 hr and 110 +/- 3% at 2 hr, while it significantly decreased to 93 +/- 2% at 4 and 5 hr and 95 +/- 2% at 6 hr (n = 8). Pretreatment with prostaglandin biosynthesis inhibitor, flurbiprofen, did not cause significant effect on the phenylephrine action, while pretreatment with alpha antagonist, phenoxybenzamine abolished it. After a single instillation of 2.5% salbutamol, it significantly decreased to 78 +/- 4% at 1 hr, 84 +/- 3% at 2 hr and 91 +/- 3% at 3 and 4 hr (n = 8), while a single instillation of 0.5% L-timolol did not show significant effect on it. Pretreatment with timolol abolished the salbutamol action. The mean aqueous flow rate in the normal rabbit as determined by this method was 3.64 +/- 0.15 microliters min-1 (n = 20).