The extent of neuronal re-uptake of 3H-noradrenaline in isolated vasa deferentia and atria of the rat

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Abstract
After pretreatment of rats with reserpine and pargyline (to inhibit vesicular uptake and monoamine oxidase, respectively) and after inhibition of catechol-O-methyl transferase (by U-0521) and in calcium-free solution, the adrenergic neurones of isolated vasa deferentia and atria were loaded with 3H-noradrenaline. The spontaneous efflux of 3H-noradrenaline and 3H-dihydroxyphenylglycol was determined, as well as the steady-state effect of two concentrations of desipramine. On the basis of a mathematical model of the adrenergic nerve ending, fractional rates (FR = rate of flux divided by tissue tritium content) were calculated for unidirectional outward diffusion, for outward transport and for neuronal re-uptake (all for 3H-noradrenaline). Although the density of adrenergic innervation is lower in atria than in vasa deferentia, neuronal re-uptake amounted to about 90% of the spontaneous efflux of 3H-noradrenaline in both tissues. While the FR for unidirectional outward diffusion was virtually the same in both tissues, the FR for outward transport of 3H-noradrenaline was more than three times higher in atria than in vasa deferentia. There is, as yet, no explanation for this pronounced difference.

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