Intrinsic neuromuscular defects in the neurogenic bladder. 1. Short‐term ultrastructural changes in muscular innervation of the decentralized feline bladder base following unilateral sacral ventral rhizotomy

The morphology of cholinergic and adrenergic muscular nerves of the feline bladder base was studied ultrastructurally 2, 3, and 4 weeks following its decentralization by unilateral sacral ventral rhizotomy. In all samples, there was widespread transsynaptic degeneration of cholinergic axon terminals and varicosities, with loss of neuroeffector junctions. This was associated with preservation of most adrenergic axons, and — especially in the 4‐week samples—with concurrent early regeneration or sprouting in many cholinergic and adrenergic axons. The findings are discussed in relation to neural ultrastructure in other known models of axonal degeneration, and to the pathogenesis of neurogenic dysfunction of the parasympathetic‐decentralized bladder. The concurrent degenerative and early regenerative axonal changes herein observed in such a bladder (1) suggest that the degeneration of cholinergic axons occurring shortly after rhizotomy is reversible, and probably is compensated for by developing adrenergic hyperinnervation; (2) support the existence of mutual peripheral cholinergic/adrenergic neurotrophism in the vesical muscularis; and (3) provide a probable structural basis for the altered motor and autonomic drug responses of the parasympathetic‐decentralized bladder.