[The effect of continuous and intravenous application of carteolol chloride on tissue blood flow in the rabbit optic nerve head]

The effect of systemic application of carteolol, which induces almost the same plasma carteolol level as obtained by a long-term instillation on rabbit eyes, on the tissue blood flow in the optic nerve head (ONH) was investigated in rabbits. The plasma carteolol levels in 27 rabbits which received 3-week instillation, intravenous injection (10, 20, 30 micrograms/kg), or continuous intravenous injection (2.5, 5, 20, 40, 80 micrograms/kg/hr) were measured by gas chromatography-negative-ion chemical ionization mass spectrometry. The plasma level with 3-week instillation was determined as 5.55 ng/ml and a continuous intravenous injection (5 micrograms/kg/hr) caused nearly the same plasma level. The intravenous injection of this dose significantly increased the ONH blood flow which was determined by the hydrogen clearance method, compared with controls from 30 minutes to 2 hours after the injection (n = 10). The vascular resistance in ONH was thought to be reduced because mean blood pressure and intraocular pressure (n = 6) were not significantly changed. The results suggest that the plasma carteolol level in rabbits after a long-term instillation can increase ONH blood flow due to a decreased vascular resistance.