Allicin-induced hypotension in rabbit eyes.

The intent of this work was to examine the actions of allicin on 1) intraocular pressure (IOP) in normal and unilaterally sympathectomized (SX) rabbits; 2) cAMP accumulation in the rabbit iris-ciliary body (ICB) and cultured nonpigmented epithelial (NPE) ciliary body cells; and 3) 3H-norepinephrine (NE) release by calculating fractional tritium overflow in response to electrical field stimulation (EFS, 5 Hz, 12 V/cm) in isolated, perfused rabbit ICBs. Allicin, one of the active compounds produced by garlic, was evaluated on IOP and it was determined that allicin (1, 2.5, or 10 micrograms), topically, but not the precursor, alliin (10 micrograms), lowered the IOP unilaterally in normal rabbits. Allicin (10 micrograms) reduced the IOP by 6 +/- 1 mmHg (n = 4) in normal rabbits at 2 hrs (maximum response) whereas no change occurred in sympathectomized rabbit eyes. Moreover, allicin (0.01, 0.1, or 1 microM) caused 40, 40, or 52% inhibition, respectively, of 3H-NE overflow in response to EFS. Isoproterenol (ISO, 1 microM) stimulated cAMP accumulation by 3.6 and 9 fold in isolated rabbit ICB and cultured NPE cells, respectively. Allicin (1 microM) had no effect on basal cAMP level while it inhibited ISO-stimulated cAMP accumulation by 40% and 23% in ICB and NPE cells, respectively. This study suggests that allicin lowered IOP, in part, by dual actions at the neuroeffector junction.