Different effects of topical prazosin and pilocarpine on uveoscleral outflow in rabbit eyes.
OBJECTIVE
To investigate the effects of topical prazosin and pilocarpine on uveoscleral outflow (Fu) in rabbits.


METHODS
Sixteen rabbits were randomly divided into the control group (5 rabbits, only topical application of normal salino in the right eye of each rabbit), Prazosin (PZ) treated group (6 rabbits, only 0.1% Prazosin eyedrop 0.1% in the right eye of each one) and Pilocarpine (PC) treated group (5 rabbits, 1% Pilocarpine eye drop in each right eye). Intraocular pressure (IOP) of bilateral eyes of each rabbit was measured before and 1 h after topical application of the eye drop. And the bilateral eyes were perfused with Fluorescein-isothiocyanate bovine serum albumin (FITC-BSA) as the tracer into the anterior chamber of each rabbit for 30 min at 90 min after topical treatment. Then the rabbits were killed for Fu measurement.


RESULTS
IOP of PZ-treated eyes decreased [(0.71 +/- 0.07)kPa] in 1 hour after PZ application. IOP of PC-treated eyes decreased [(0.70 +/- 0.08)kPa] in 1 hour after PC application. The average value of Fu was (0.176 +/- 0.048) microliter/min in control eyes. The average value of Fu in PZ-treated eyes was (0.339 +/- 0.018) microliter/min. The average value of Fu in PC-treated eye was (0.123 +/- 0.022) microliter/min.


CONCLUSIONS
Both of PZ and PC can decrease IOP in rabbits following topical application. Topical PZ can increase Fu in rabbits and this is one of the mechanisms of PZ-induced IOP decrease. Topical PC can prevent Fu. PC decreases IOP not through uveoscleral pathway. This study demonstrates that uveoscleral pathway plays an important role in aqueous humor drainage. PZ may be a novel drug for decreasing IOP. FITC-BSA is an effective tracer for studying uveoscleral pathway.
Department of Ophthalmology, Second Hospital, Xi'an Jiaotong University, Xi'an 710004, China.
Jianming
J
Wang
Yanping
Y
Song
Baichao
B
Ren
Naixue
N
Sun
Yinggui
Y
Yu
Haitao
H
Hu
D000287:Administration, Topical; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism*; D005260:Female; D007429:Intraocular Pressure / Q000187:drug effects; D008297:Male; D018721:Muscarinic Agonists / Q000494:pharmacology; D010862:Pilocarpine / Q000494:pharmacology*; D011224:Prazosin / Q000494:pharmacology*; D011817:Rabbits; D011897:Random Allocation; D012590:Sclera / Q000378:metabolism*; D014129:Trabecular Meshwork / Q000378:metabolism; D014602:Uvea / Q000378:metabolism*
D000317:Adrenergic alpha-Antagonists; D018721:Muscarinic Agonists; D010862:Pilocarpine; D011224:Prazosin