Quantitative assessment of ocular norepinephrine concentration in the rabbit using liquid chromatography with...

An assay technique that utilizes liquid chromatography with electrochemical detection to determine the norepinephrine (NE) concentration of the rabbit aqueous humor (AH) and iris-ciliary body (ICB) is discussed. NE concentration was monitored in control preparations as well as in experiments involving stimulation of the cervical sympathetic nerve (CSN) or 24 h following extirpation of the superior cervical ganglion. In 15 control rabbits, the baseline AH NE concentration was determined to be 7.2 and 7.8 ng/ml in the left and right eyes, respectively. Prolonged unilateral electrical stimulation of the CSN increased the AH NE concentration to 59.0 +/- 1.2 ng/ml on the stimulated side. Pretreatment with cocaine (12.5 mg/kg) and subsequent stimulation of the CSN increased the NE in the AH to 93.7 +/- 1.3 ng/ml on the stimulated side, and raised the baseline AH NE of the control (non-stimulated) side to 25.9 +/- 5.0 ng/ml. The baseline concentration of NE in the ICB was 5.4 +/- 0.8 micrograms/g. 24 h after a unilateral removal of the superior cervical ganglion, the NE content of the ICB was depleted by more than 90% in the ganglionectomized eye with no apparent change in the level of NE in the AH. The accurate analysis of catecholamines in the AH, ICB and other parts of the eye may be useful in providing information as to the extent of innervation and the possible role of sympathetic nerve supply in the overall control of AH dynamics.(ABSTRACT TRUNCATED AT 250 WORDS)