Reinnervation of the transplanted vas deferens: differential recovery of various biochemical and pharmacological parameters

Summary

Biochemical and pharmacologcial parameters were used to follow the innervation characteristics of the rat was deferens transplanted (T) to the caecum. After about 5 months, a regeneration of autonomic nerves was clearly shown: first, by a complete recovery of neuronal uptake, indicated by: a) potentiation by cocaine of epinephrine (EPI) dose-response curves (T=1.47±0.25, controls (C)=1.50±0.14 log units); b) reversion to normal levels of pD₂ values for norepinephrine (NE) and EPI (T=6.6.±0.1; 7.0±0.1, and C=6.4±0.1; 6.9±0.1, respectively); second, a partial restoration of nerve terminals, and corresponding pools of NE, which was seen through histofluorescence and was indicated by a percent increase of: a) NE content, 47% (T=3.8±0.8, C=8.5±0.7 =μg/g); b) dopamine-β-hydroxylase (DBH) activity, 37% (T=136±80, C=364±15 nmol(hr.g); c) release of NE by 57 mM-potassium, 23% (T=33.0±12.0, C=147±14 ng/g. 5 min). Yet, two peculiarities of denervated organs remained practically unchanged even after 5-month transplantation: NE supersensitivity, measured by the relative responsiveness (p) ratio (T=0.96±0.02, C=0.69±0.03), and tyramine-induced contraction, that was recovered by only 14% (T=10.0±2.4, C=72.0±3.5 mm). This differential recovery of the forementioned parameters is discussed in the light of receptor mechanisms and functional changes following reinnervation.