Development of supersensitivity to methacholine in the rat detrusor following either parasympathetic denervation or decentralization

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Abstract
The male rat urinary bladder belongs to those few structures where both the post- and preganglionic parasympathetic nerves are accessible for severance. The sensitivity to the parasympathomimetic drug methacholine of muscle strips of either denervated or decentralized bladders was examined in vitro. One wk postoperatively denervated and decentralized bladders were sensitized to the same degree, ED50 (median effective dose) values being 4 times less than the ED50 of unoperated control bladders. In contrast to the decentralized bladders the supersensitivity in the denervated ones was found to have increased further when tested 4 wk postoperatively, the ED50 value being about 20 times less than that of controls. These findings are in agreement with Cannon''s "law of denervation". The results are discussed in relation to possible mechanisms behind the phenomenon of supersensitivity.