title: 4-aminopyridine transiently increases intraocular pressure in rabbits.
abstract: The purpose of this study is to determine the mechanisms of action involved in the ocular hypertension induced by 4-aminopyridine (4-AP), a voltage-dependent potassium (K+) channel blocker, in rabbits. Topical application of 4-AP elevated intraocular pressure (IOP). This action caused increases in the aqueous flow rate as well as aqueous levels of protein and norepinephrine. In isolated iris-ciliary body preparations, 4-AP (0.01, 0.1, 1 mmol/l) caused dose-related increases in field-stimulated norepinephrine release by 43, 222 and 243%, respectively. Taken together, the IOP-elevating effect evoked by 4-AP was associated with enhancement of aqueous norepinephrine levels and norepinephrine release from sympathetic nerves of the iris-ciliary body. These results demonstrate that the 4-AP-sensitive K+ channels in sympathetic nerves and the ciliary epithelium are the potential sites of action of the 4-AP-induced ocular hypertension.
authors.affiliation: Department of Pharmacology/Toxicology, Morehouse School of Medicine, 720 Westview Drive, Atlanta, GA 30310-1495, USA.
authors.forename: Robin R
authors.initials: RR
authors.lastname: Socci
authors.forename: Eugenia
authors.initials: E
authors.lastname: Chu
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Bayorh
authors.forename: Teh-Ching
authors.initials: TC
authors.lastname: Chu
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology*; D000818:Animals; D001082:Aqueous Humor / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D007429:Intraocular Pressure / Q000187:drug effects*; D008297:Male; D009638:Norepinephrine / Q000378:metabolism; D009798:Ocular Hypertension / Q000209:etiology; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D011680:Pupil / Q000187:drug effects*; D011817:Rabbits
chemical_list: D026902:Potassium Channel Blockers; D015761:4-Aminopyridine; D009638:Norepinephrine