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

Abstract

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 densecored 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.