A comparative study of changes in innervation and development of supersensitivity in the rat vas deferens after...

The relationship between morphological and functional changes in adrenergic nerves and the development of supersensitivity in the rat vas deferens was comparatively investigated after surgical denervation, chemical sympathectomy by 6-hydroxydopamine, daily treatment of animals with reserpine, or local application of colchicine to the hypogastric plexus. The order of ability to produce supersensitivity, as judged by the extent of the increase in the pD2 value of norepinephrine and the maximum response to norepinephrine, was as follows: denervation = colchicine greater than 6-hydroxydopamine greater than reserpine. These procedures produced alterations in morphological characteristics of the nerve ending with severeness of degeneration in the following order: denervation greater than 6-hydroxydopamine greater than colchicine greater than reserpine. Twitch contractions induced by transmural nerve stimulation were slightly reduced after colchicine or 6-hydroxydopamine treatment, markedly reduced by reserpine, and abolished by denervation. Therefore, the development of supersensitivity in the rat vas deferens is not necessarily in proportion to the morphological or functioning changes in adrenergic nerves. The results suggest that some neurofactor, e.g. trophic factor, is involved in the control of the drug sensitivity of smooth muscle in addition to the neurotransmitter itself.