title: Effects of ethacrynic acid on intraocular pressure of anesthetized rats.
abstract: Ethacrynic acid (ECA) lowers intraocular pressure (i.o.p.) by an effect usually ascribed to increased drainage of aqueous humor by the trabecular meshwork. Here, we describe the effects of a continuous 2-hr intracameral infusion of balanced salt solution (BSS), with or without 2 mM ECA (sodium salt), on IOP of pentobarbital anesthetized rats. The infusion was divided into a constant (0.05 microliter/min) and a periodic (0.25 microliter/min) component that cycled 4 min on then 4 min off. This permitted the calculation of dynamic changes in resistive (trabecular and uveoslceral drainage) and nonresistive (aqueous synthesis, episcleral venous pressure) components of IOP by fitting a second-order transfer function to the responses. ECA markedly blunted the BSS-induced rise in IOP (P < 0.01). The rise in resistive mechanisms (ocular impedance) was transiently blunted by ECA (P < 0.05) during the third and fourth 8-min cycles, and nonresistive mechanisms were reduced by ECA from cycles 3-10 (P < 0.05). Then, at the end of the infusion, the control and ECA dynamic values were similar (P < 0.05), although IOP of ECA-treated rats was still slightly reduced (P < 0.05). The most likely explanation is a summation of small changes in both resistive and nonresistive components of IOP dynamics. Systemic blood pressure was unchanged within either group. The well-known effects of ECA on the trabecular meshwork, alone, are insufficient to explain the dynamic changes in IOP observed in this model.
authors: Department of Pharmacology, College of Medicine, Pennsylvania State University, Hershey 17033, USA.
authors: R V
authors: RV
authors: Searles
authors: M
authors: M
authors: Johnson
authors: V
authors: V
authors: Shikher
authors: C D
authors: CD
authors: Balaban
authors: W B
authors: WB
authors: Severs
mesh_terms: D000758:Anesthesia; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004976:Ethacrynic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D007260:Infusion Pumps; D007429:Intraocular Pressure / Q000187:drug effects* / Q000502:physiology; D008297:Male; D008954:Models, Biological; D010424:Pentobarbital; D051381:Rats; D017207:Rats, Sprague-Dawley; D014129:Trabecular Meshwork / Q000187:drug effects / Q000502:physiology
chemical_list: D010424:Pentobarbital; D004976:Ethacrynic Acid