title: The central ocular hypotensive effect of clonidine.
abstract: Clonidine was administered into the left vertebral artery of anesthetized cats. A dose-response curve of the lowering effect on intraocular pressure (IOP) has been made and compared with the dose-response cure obtained after intravenous administration. A more pronounced decrease in IOP after the first route of administration became evident. The effect is not secondary to a stronger reduction of blood pressure by centrally injected clonidine. Distribution experiments with 14C-clonidine revealed no direct connection between the vertebral arteries and the blood supply of the eye. For 2 h the concentrations in the eye are somewhat lower than after intravenous administration. Therefore, the IOP-lowering effect is not due to a direct influence of clonidine on the eye. It is submitted that the clonidine-induced reduction in IOP is at least in part due to a central mechanism, in which the stimulation of central alpha-adrenoceptors and adrenergic neurons may be involved. The relevance of this hypothesis with regard to a possible central regulation of IOP is discussed.
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D003000:Clonidine / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005123:Eye / Q000378:metabolism; D005260:Female; D007261:Infusions, Intra-Arterial; D007429:Intraocular Pressure / Q000187:drug effects*; D008297:Male; D010883:Piperoxan / Q000494:pharmacology; D014711:Vertebral Artery
chemical_list: D010883:Piperoxan; D003000:Clonidine