Atrial sympathetic nerves after perfusion of the rabbit heart with low sodium solutions containing potassium chloride or urea--a biochemical, histochemical and fine structural study

Parallel changes in ultrastructure and noradrenaline content of nerve terminals in rat vas deferens following transmitter release

Transmural electrical stimulation and exposure to incubation media where some or all of the Na+ had been replaced with K+ were used to elicit transmitter release. Changes in noradrenaline content and ultrastructure of the nerve terminal varicosities in rat vas deferens were measured. Electrical stimulation in the presence of 4-aminopyridine had little effect, but high [K+] solutions caused a parallel reduction in noradrenaline content and the number of small dense-cored vesicles; large dense-cored vesicles showed no change, and small clear vesicles increased in number. In spite of a reduction in total vesicle number there was no evidence of expansion of the varicosity membrane. The parallel fall in noradrenaline content and in the number of small dense-cored vesicles suggests that the latter are the source of the released noradrenaline under the conditions of high [K+] stimulation we have used.

The use of the De Deckere-Ten Hoor preparation for study of nicotinic and potassium-evoked dopamine beta-hydroxylase release from the rabbit heart

1. Dopamine beta-hydroxylase (DBH) and noradrenaline were determined both in the venous effluent (perfusate) and in the transmyocardial fluid (TMF) collected from the apex of the rabbit isolated heart which was prepared according to De Deckere and Ten Hoor (1977) and perfused with Tyrode's solution at 20 ml/min. 2. Perfusion for 2 min with the nicotinic drug, p-aminophenethyl-trimethylammonium (PAPETA), both in the absence of presence of atropine evoked noradrenaline overflow into the perfusate and TMF that was maximal in the 0-2 min sample and declined from maximum with a t 1/2 of 0.6 min. DBH was released into TMF with the maximum from 2-4 min and a t 1/2 of decline of 5.6 min. 3. High K-low Na solution containing 54 mM KCl was perfused for 4 min. The maximum outputs of noradrenaline into the perfusate and TMF occurred between 2 and 4 min and that of DBH into TMF 2 min later. The t 1/2 of decline from the maxima were similar to those after PAPETA but the output ratio DBH/noradrenaline was 5 times that after PAPETA. 4. Both chemical stimuli were not observed to increase the DBH content of the perfusates. The noradrenaline concentration in the TMF was 3 times that in the perfusates. 5. It is concluded that TMF reflects concentration changes in the synaptic region more truly than the venous effluent does. TMF is particularly suitable for determination of DBH output of the heart; the DBH concentration is higher than in the perfusate and its washout faster than from the conventional Langendorff preparation.