The effect of reserpine treatment on the extraneuronal uptake of [3H]-isoprenaline into rat atria.

Treatment of rats with reserpine (1 mg kg-1 day-1) for up to 7 days resulted in a marked decrease in a corticosterone-sensitive component of the extraneuronal accumulation of [3H]-isoprenaline into their atria. The change in extraneuronal uptake did not appear to be due to a direct action of reserpine on the uptake mechanism, since it was several days before the treatment had a significant effect on the accumulation of [3H]-isoprenaline. Further, reserpine in vitro did not inhibit extraneuronal uptake. The reserpine-induced change in the accumulation of [3H]-isoprenaline was not an artifact due to changes in water balance, ion distribution, extracellular space or tissue atrophy. Nor was the change due to an increase in the efflux of [3H]-isoprenaline from the tissue. These experiments support the suggestion that the extraneuronal uptake is dependent upon a functional adrenergic innervation.