Abstract

The effect of chronic treatment with pargyline (5 mg/kg/day) and l-dopa (50 mg/kg/day) for a period of three weeks was invesigated on the norepinephrine content of spleen and coeliac ganglia and on the release of norepinephrine from the perfused spleen of the cat after pre- and postganglionic nerve stimulation. Pargyline pretreatment had no significant effect on the norepinephrine content of the spleen but increased the concentration of norepinephrine of the coeliac ganglia by almost 2- to 3-fold. On the other hand, administration of l-dopa led to about 60% depletion of norepinephrine stores of the spleen without significantly altering the norepinephrine content of the coeliac ganglia. Studies on the release showed that pargyline very effectively lowered norepinephrine output from spleen after stimulation of the preganglionic compared to the postganglionic nerves. Treatment with l-dopa caused a marked reduction in norepinephrine output after postganglionic nerve stimulation. It is suggested that the hypotension observed after prolonged treatment with pargyline and l-dopa probably is due to inhibition of the sympathetic tone. Pargyline inhibits ganglionic transmission and l-dopa depletes the norepinephrine stores of the sympathetically innervated organs.