Release of noradrenaline from the ligated cat hypogastric nerve

After in vivo ligation for 24 of the cat hypogastric nerve, large amounts of noradrenaline (NA) and dopamine beta-hydroxylase (DBH) accumulated in the nerve segment immediately proximal to the ligature (P 1). In vitro incubation of 24-h-ligated nerves ((segments P1 and P2) in oxygenated Krebs solution at 37 degrees C in the presence of the ionophore X537A or high K+ concentrations caused a marked release of endogenously accumulated NA into the incubation medium. High-K+-evoked release was entirely dependent on extracellular Ca2+. Electrical nerve stimulation caused an 80% tissue NA loss, but the transmitter could not be found in the medium as intact NA. These results suggest that the in vivo ligated cat hypogastric nerve may serve as a useful model of adrenergic nerve terminals free of effector cells.