Recovery of dopamine in peripheral adrenergic nerves after reserpine treatment.

The endogenous levels of dopamine (DA) in the rat heart and submaxillary gland after a single, large dose of reserpine (10 mg/kg i.p.) were reduced to near zero within 1 h and were restored to normal within 48 h, while the noradrenaline (NA) levels reacted much more slowly. The data suggest that newly formed DA is rapidly taken up by the reserpinesensitive mechanism of the amine storage granules. The more rapid restoration of DA than of NA levels may be due to preferential release of newly formed NA by the nerve impulse. Electrical stimulation of the cervical sympathetic with 5 Hz for 30 min 4 h after the administration of reserpine increased the DA level of the submaxillary gland of the stimulated side, suggesting an increased tyrosine hydroxylase activity during stimulation, also in nerve terminals affected by reserpine. The use of an inhibitor of monoamine oxidase (pargyline) and/or an inhibitor of dopamine beta-hydroxylase (FLA-63) did not significantly alter the increase of DA following nerve stimulation, suggesting DA was protected by granular uptake. The stimulation-induced increase in DA was, however, much less in reserpine-treated than in normal animals, demonstrating the importance of the reserpine-sensitive uptake mechanisms for preserving newly formed DA.