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Intrinsic vasomotricity and adrenergic effects in a model of isolated rabbit eye
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Orientador(es)
Resumo(s)
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 lg ⁄ ml) were inhibited by intra-arterial administration
of the selective a1-adrenergic antagonist, prazosin (0.5 mg⁄ ml), as well as the
non-selective a-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
Descrição
Título da Revista: Acta Ophthalmologica Scandinavica
Palavras-chave
Adrenergic drugs Isolated perfused rabbit eye Spontaneous vasomotion