The recovery of noradrenaline in adrenergic nerve terminals of the rat after reserpine treatment

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Abstract
Tissue concentrations of endogenous noradrenaline in heart, submaxillary gland, and gastrocnemic muscle have been examined after one large dose of reserpine (10 mg/kg) to rats. After the initial depletion of the amine, the concentration started to rise between 24 and 36 h. For about one week thereafter the amine recovery proceeded comparatively fast, then the rate of the recovery slowed. Between the 4th and the 6th weeks there was a pronounced drop in the noradrenaline concentration in all three tissues, apparently beginning in the 4th week with a maximal decrease of about 20% in the 5th week after reserpine. Thereafter the concentrations increased to approach normal about 6 weeks after reserpine. These results are discussed in relation to the axonal down-transport of newly formed amine storage granules and to the life-span of these granules in the nerve terminals. The different parts of the noradrenaline recovery curve appeared to reflect the axonal down-flow of granules. A theoretical recovery curve was calculated, based on granular transport. This curve was similar to the observed recovery curve. The claim is made that the recovery of adrenergic function and noradrenaline levels after reserpine is due to a down-transport of newly formed, amine storage granules to the nerve terminals. There seems little need for the theory that the storage function reappears in old, reserpine-blocked granules, as a mechanism for noradrenaline recovery after a large dose of reserpine.