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Olprinone, a phosphodiesterase III inhibitor, does not affect hypoxia-induced pial arteriolar dilatation in rabbits

[L’olprinone, un inhibiteur de la phosphodiestérase III, n’a pas d’effet sur la dilatation artériolaire pie-mérienne chez les lapins]

From the Department of Anesthesiology Institute of Clinical Medicine University of Tsukuba, Tsukuba, Japan.

Address correspondence to: Dr. Masayuki Miyabe, Department of Anesthesiology, Institute of Clinical Medicine, University of Tsukuba, Tsukuba 305-8575, Japan. Phone: 81-298-53-3088; Fax: 81-298-53-3092; E-mail: miyabe{at}md.tsukuba.ac.jp

Purpose: Olprinone, a phosphodiesterase III inhibitor, is used for the treatment of heart failure or asthma. Such patients may suffer from hypoxia. However, the effect of olprinone on the cerebral vasodilator response to hypoxia remains unclear.

Methods: Rabbits were anesthetized and ventilated mechanically. The pial arteriolar diameter was determined using a cranial window and intravital microscopy. Hypoxia was induced twice in the same animal by reducing FIO₂ to 0.1. The first episode was induced during an infusion of saline, and the second during an infusion of saline (saline group; n = 8) or olprinone (1 µg•kg^-1•min^-1, OLP1 group; n = 8 or 10 µg•kg^-1•min^-1, OLP10 group; n = 8). The pial arteriolar responses to hypoxia were recorded and compared between the two episodes of hypoxia in each group.

Results: Blood gas data in the first hypoxic challenge were identical to those in the second challenge in each group. Pial arteriolar diameter increased significantly during hypoxia. In arterioles between 50–100 µm diameter, first and second hypoxia-induced pial arteriolar dilatation in OLP1 were 13 ± 6% and 10 ± 7% respectively (P = 0.574 ) and those in OLP10 were 16 ± 6% and 15 ± 7% respectively (P = 0.606). In arterioles between 25–50 µm, the results were the same as in arterioles between 50–100 µm.

Conclusion: Olprinone does not affect the hypoxia-induced dilatation of pial arterioles in pentobarbital anesthetized rabbits.