An Inhibitor of Cerebral Uptake of Noradrenaline in Jaundiced Blood Plasma

Abstract

The permeability of the blood–brain barrier to noradrenaline was estimated in rats with bile duct ligation by intracarotid injection of [¹⁴C]-l-noradrenaline, ³H₂O, and [^113mIn]ethylene diamine tetraacetate (EDTA) under pentobarbitone anaesthesia. Brain uptake of [¹⁴C]noradrenaline was expressed as a percentage of that of ³H₂O (brain uptake index, BUI) and corrected for the “blood background” by the ^113mIn. The BUI of noradrenaline (1.20 ± 0.19) was not increased in jaundice (0.78 ± 0.18). The capacity of oxygenated homogenates of rat brain to remove noradrenaline was measured. The presence of jaundiced plasma always caused a substantial suppression of noradrenaline removal. No effect of jaundice on specific radioactive assays for catechol-O-methyl transferase (COMT) or monoamine oxidase (MAO) could be demonstrated.