title: Intrinsic vasomotricity and adrenergic effects in a model of isolated rabbit eye.
abstract: OBJECTIVE
  We aimed to investigate the responsiveness of the ocular arteries to adrenergic drugs in a model of perfused isolated rabbit eye.
  
  
  METHODS
  Rabbit external ophthalmic arteries (n = 15) in a head-mounted preparation were cannulated and the retinal and uveal vasculature perfused at a constant flow with warmed tyrode. The three-way polypropylene catheter was further connected to a pressure transducer and intraluminal pressure was taken as a measure of vascular resistance. Effects of intra-arterial injections of phenylephrine (group A, n = 5), prazosin (group B, n = 5) and phentolamine (group C, n = 5) on the recorded pressure were obtained. Student's paired-t test and one-way analysis of variance were used for statistical analysis (p < 0.05).
  
  
  RESULTS
  Intrinsic vasomotricity was observed in all preparations prior to any drug administration. Phenylephrine produced an increase in total vascular resistance. Intrinsic vasomotricity became more evident, showing a lower frequency but higher amplitude of oscillations. Evoked vasomotor responses with phenylephrine (250 microg/ml) were inhibited by intra-arterial administration of the selective alpha(1)-adrenergic antagonist, prazosin (0.5 mg/ml), as well as the non-selective alpha-adrenergic antagonist phentolamine (6 mg/ml).
  
  
  CONCLUSIONS
  Rabbit external ophthalmic arteries showed spontaneous contractions under constant perfusion. Phenylephrine elicited a vasoconstrictor response that was inhibited by adrenergic antagonists. In addition, the intrinsic vasomotricity was enhanced by phenylephrine and blocked by adrenergic antagonists. These results show that under in vitro perfusion the territory presents similar responses to adrenergic drugs to those observed in in vivo models and also provides evidence of myogenic autoregulatory properties in the rabbit ophthalmic artery and/or choroid.
authors.affiliation: Clinical Department, Centre for Interdisciplinary Investigation into Animal Health, Faculty of Veterinary Medicine, Technical University of Lisbon, Lisbon, Portugal. esmeralda@fmv.utl.pt
authors.forename: Esmeralda
authors.initials: E
authors.lastname: Delgado
authors.forename: Carlos
authors.initials: C
authors.lastname: Marques-Neves
authors.forename: Isabel
authors.initials: I
authors.lastname: Rocha
authors.forename: José
authors.initials: J
authors.lastname: Sales-Luís
authors.forename: Luis
authors.initials: L
authors.lastname: Silva-Carvalho
mesh_terms: D018663:Adrenergic Agents / Q000008:administration & dosage*; D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage; D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage; D000818:Animals; D001158:Arteries / Q000187:drug effects; D005123:Eye / Q000098:blood supply*; D005260:Female; D006706:Homeostasis; D066298:In Vitro Techniques; D007269:Injections, Intra-Arterial; D008297:Male; D023421:Models, Animal; D010646:Phentolamine / Q000008:administration & dosage; D010656:Phenylephrine / Q000008:administration & dosage; D011224:Prazosin / Q000008:administration & dosage; D011817:Rabbits; D012039:Regional Blood Flow / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects; D014666:Vasomotor System / Q000187:drug effects* / Q000503:physiopathology*
chemical_list: D018663:Adrenergic Agents; D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D010656:Phenylephrine; D011224:Prazosin; D010646:Phentolamine