Noradrenaline Uptake Properties of the Anococcygeus Muscle of the Rat

Noradrenaline (NA) uptake was measured in the anococcygeus by two methods: quantitative fluorescence microscopy and radioactive tracer techniques. A pharmacological analysis of the contribution of adrenergic nerve, smooth muscle, and nonspecific binding to collagen and basement membrane was attempted by studying the effects of desmethylimipramine and phenoxybenzamine on uptake. The importance of metabolic degradation in the process of NA accumulation was estimated by examining the effect of the combined use of iproniazid to inhibit monoamine oxidase and of β-thujaplicin to inhibit catechol O-methyltransferase.The results suggest that NA accumulation in this tissue at concentrations below 2 × 10−6 g/ml was almost entirely due to uptake into adrenergic nerves and to nonspecific binding. At higher concentrations of NA, above 2 × 10−6 g/ml, uptake into the smooth muscle cells began to contribute increasingly to the total accumulation. Inhibition of the metabolic enzymes increased the fluorescence of smooth mu...