Effects of reserpine and oxypertine on accumulation of norepinephrine in mitochondrial fraction of brain stem of guinea pig.

Recently, the subfractionation technique to separate nerve endings and other components of mitochondrial fraction has demonstrated the subcellular distributions of norepinephrine, 5-hydroxytryptamine and acetylcholine in the brain. Therefore, by this subfractionation technique, it seems to be interesting to examine which subfractions are affected and fail to accumulate norepinephrine when they are incubated with norepinephrine in the presence of reserpine or oxypertine. In this experiment, mitochondrial fraction was prepared from 0.25 M sucrose homogenate of the brain stem of guinea pig and this was incubated with "C-norepinephrine in the presence of reserpine or oxypertine at 30°C for 30 minutes. After incubation, the mitochondrial fraction was placed on the top of five layers of 0.6, 0.8, 1.0, 1.2 and 1.4 M sucrose and this was centrifuged at 90,000 x g for 60 minutes. Thus, the mitochondrial fraction was clearly separated into seven subfractions. Radioactivity of each fraction was assayed in a liquid scintillation counter. Radioactivity of norepinephrine in each fraction of the experiment is shown in Fig. 1. In the control experiment, higher radioactivities were found in B, E and F fractions, which were supposed to be corresponded to the fraction containing myeline fragments, cholinergic nerve endings and noncholinergic nerve endings, respectively. Reserpine (final conc. of 10-3 M) produced the decrease in radioactivities of E and F fractions, while oxypertine (final conc. of 10-3 M) decreased the radio-