Effect of splenic nerve stimulation on the contents of noradrenaline, ATP and sulphomucopolysaccharides in noradrenergic vesicle fractions from the cat spleen

Abstract

In order to assess the effect of splenic nerve stimulation on the contents of noradrenaline, ATP and 35S-labelled compounds in noradrenergic vesicles from the spleen, experiments were carried out on the cat spleen in situ, its frontal portion being used as control. Particulate fractions containing noradrenergic vesicles were isolated on Ficoll gradient centrifugation of homogenates from both portions of the spleen. The cats received phenoxybenzamine (10 mg/kg) and imipramine (5 mg/kg) to inhibit the contractive response of the spleen to nerve stimulation and the reuptake of noradrenaline (NA) into nerve terminals. Administration of the drugs did not significantly affect the levels of NA, ATP and 35S (presumably in sulphomucopolysaccarides, SMPSs). In response to prolonged stimulation of the splenic nerve a significant loss of NA from noradrenergic vesicles occurred, whereas levels of ATP and 35S-labelled compounds remained unchanged. The results indicate that a discharge of NA in response to nerve stimulation is not accompanied by simultaneous discharge of ATP and SMPSs.