Uptake and Release of u‐Methyl‐Noradrenaline in Vitro after Reserpine Pretreatment A Histochemical Study

The reserpine‐rcsistent uptake and storage of α‐methyl‐noradrenaline in vitro were investigated in thr adrenergic nerves of the rat iris. After reserpine pretreatment, an effective accumulation of α‐methyl‐noradrenaline took place intraneuronally. The amine remained intraneuronally for several hours ivhen incubated in amine‐free medium at 37°C. The morphological appearancc changed during the incubation in a manner suggesting that part of the amine was bound to an intraneuronal structure, which might be the amine storage granules. Interference with energy generation in the ˜ncdiurn, as well as chemical depolarization by increasing potassium ion concentration in the inediuin, inhibited accumulation and caused a rapid release of α‐methyl‐noradrenaline. Protriptyline inhibited the uptake of α‐methyl‐noradrenaline efficiently, and also enhanced the disappearance of accumulated amine. Although (+)‐amphetamine was less potent in preventing uptake. it produced a rapid rclease of the amine.