title: Acetylcholine can exert two opposite effects on uveal flow in isolated arterially perfused eyes of cats and rabbits.
abstract: Acetylcholine (Ach) has an effect on IOP and uveal flow. It elevates IOP in cats but not in rabbits in eserinized preparations. A fall in IOP induced by epinephrine (epi) or norepinephrine (nor-epi) is partly reversed by the addition of Ach. Ach has a dual effect on uveal flow in both cats and rabbits. It causes vasoconstriction in high concentrations or in the presence of eserine (Es). The constriction is presumably maximal in the choroidal (efferent) part of the ciliary processes. Ach may also cause vasodilatation after preconstriction of uveal with adrenergic agents. The dilatation is probably located in the afferent vessels of the ciliary processes. The dose of Ach required for dilating preconstricted uveal vessels is at least 3 magnitudes lower than the dose for constricting the uveal vasculature. We propose that uveal vessels contain two kinds of muscarinic receptors, one inhibitory and another excitatory.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002415:Cats; D004347:Drug Interactions; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010830:Physostigmine / Q000494:pharmacology; D011817:Rabbits; D011976:Receptors, Muscarinic / Q000187:drug effects; D012039:Regional Blood Flow / Q000187:drug effects; D014602:Uvea / Q000098:blood supply*; D014661:Vasoconstriction / Q000187:drug effects*; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D011976:Receptors, Muscarinic; D001285:Atropine; D010830:Physostigmine; D000109:Acetylcholine; D009638:Norepinephrine; D004837:Epinephrine