Avaliação dos efeitos da vasopressina exogena sobre a pressão intra-ocular de coelhos

AUTOR(ES)
DATA DE PUBLICAÇÃO

2001

RESUMO

Purpose. To compare the central, peripheral and local effects of exogenous arginine vasopressin on intra-ocular pressure (IOP) in rabbits and to identify the receptor mechanisms associated with these effects. Methods. Young adult New Zealand albino rabbits were housed under a daily 12-hour light and 12-hour dark cyc1e. In the early light period, bolus injections of vasopressin or desmopressin (a specific V2receptor agonist) were given either to the central nervous system (CNS) or to the ear vein in groups of 7-9 conscious rabbits. Test peptides were delivered to the CNS through an implanted cannula to the 3rdventric1e. Injections of isotonic saline solution served as the controI. Bilateral IOP was monitored for up to 6 hours and dose-response curves were generated. Central and peripheral effects of vasopressin on IOP were further examined by the pretreatment with a selective VI receptor antagonist. To investigate whether or not vasopressin can influence IOP by intra-ocular mechanisms, we performed intravitreal or anterior chamber injections of vasopressin in groups of 6 rabbits. The contralateral eye received isotonic saline solution as the controI. Bilateral IOP was monitored for up to 6 hours. The responses in IOP were analyzed using the Student s t-test. Results. A dose-dependent elevation of IOP was observed after gintracerebroventricular injections of vasopressin. The IOP elevation was completely blocked by the pretreatment with the VI antagonist given to the 3rdventric1e. Following intravenous injections of vasopressin, significant reductions of IOP were observed. The reductions of IOP were completely blocked by the pretreatment with the VI antagonist. Intracerebroventricular or intravenous injections of desmopressin had no effect on IOP. Following the intravitreal or anterior chamber injection of vasopressin, significant reductions ofIOP were observed. Intravitreal or anterior chamber pretreatment with the V- 1 receptor antagonist prevented the reductions ofIOP following the intravenous injection of vasopressm Conclusions. Bolus intracerebroventricular and intravenous injections of vasopressin cause opposite effects on IOP. Intracerebroventricular injections ofvasopressin increase IOP while peripheral and local injections of vasopressin decrease IOP. The central and peripheral effects ofvasopressin on IOP are mediated via the VI receptors

ASSUNTO(S)

vasopressina glaucoma pressão intra-ocular

ACESSO AO ARTIGO

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