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Intrinsic vasomotricity and adrenergic effects in a model of isolated rabbit eye
Author(s) -
Delgado Esmeralda,
MarquesNeves Carlos,
Rocha Isabel,
SalesLuís José,
SilvaCarvalho Luis
Publication year - 2009
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.2008.01285.x
Subject(s) - phenylephrine , phentolamine , prazosin , adrenergic antagonist , adrenergic , medicine , perfusion , antagonist , vasoconstriction , vascular resistance , anesthesia , adrenergic receptor , blood pressure , chemistry , propranolol , receptor
. Purpose: 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 μg/ml) were inhibited by intra‐arterial administration of the selective α 1 ‐adrenergic antagonist, prazosin (0.5 mg/ml), as well as the non‐selective α‐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.