title: Effects of a beta-adrenergic blocking agent timolol on intra ocular pressure responses induced by stimulation of cervical sympathetic nerve in the cat.
abstract: We clarified whether the intraocular pressure (IOP) response elicited by stimulation of the cervical sympathetic nerve (CSN) is influenced by changes in the baseline of IOP level and by beta-adrenergic blockade. The CSN was stimulated electrically for 30 seconds (10 V, 0.1-100 Hz, 2 milliseconds pulse duration) in urethane (100 mg/kg i.v.)-chloralose (50 mg/kg i.v.)-anesthetized, paralyzed cats. The IOP was monitored manometrically, and a controlled saline infusion was delivered into the anterior chamber to gradually increase IOP. CSN stimulation was delivered at the various baseline IOP levels so obtained. When required, a beta-adrenergic blocker timolol (2%) was delivered into the conjunctival cul-de-sac. The normal IOP in our cats was 25+/-3 mmHg. This value decreased transiently on CSN stimulation. The amplitude of this IOP response depended on stimulus frequency and the pre-stimulus baseline IOP level. Topical administration of timolol increased the IOP response to CSN stimulation at a given baseline level. These results suggest that beta-adrenergic blockade increases the alpha-adrenergic mediated-IOP reduction elicited by CSN stimulation at given baseline IOP level.
authors.affiliation: Department of Ophthalmology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Naito
authors.forename: H
authors.initials: H
authors.lastname: Izumi
authors.forename: K
authors.initials: K
authors.lastname: Karita
authors.forename: M
authors.initials: M
authors.lastname: Tamai
mesh_terms: D000320:Adrenergic Fibers / Q000502:physiology*; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D002415:Cats; D002574:Cervical Vertebrae; D004558:Electric Stimulation; D005123:Eye / Q000187:drug effects* / Q000378:metabolism; D007429:Intraocular Pressure / Q000187:drug effects*; D013999:Timolol / Q000494:pharmacology*
chemical_list: D000319:Adrenergic beta-Antagonists; D013999:Timolol