| Abstract: | We have shown previously that myofibers of the male feline rhabdosphincter are innervated by somatomotor end-plates as well as nonspecialized surface junctions by autonomic cholinergic and adrenergic axons. Shortly after sacral ventral rhizotomy, the somatomotor cholinergic axons innervating the plates disappear, but the autonomic cholinergic and adrenergic surface junctions are preserved. In the present study, the eventual pattern of innervation of the somatically denervated rhabdosphincter is described. Four to ten weeks after denervation there was (1) progressively marked sprouting of nonmyelinated cholinergic and adrenergic axons, with an increasingly prominent probable copeptidergic component of both axon types; (2) preservation and possibly increase in the number of autonomic surface junctions; and (3) re-innervation of the initially nerveless end-plates by autonomic cholinergic and/or adrenergic axons, occasionally with cholinergic/adrenergic axoaxonal synapses. Based on these and our previous observations, it is concluded that any neural control that the denervated rhabdosphincter may eventually have is purely autonomic, and may in part be achieved via its original end-plates. The significance of our findings with respect to the physiology and pharmacology of the rhabdosphincter (incontrast to other striated muscle) and its possible role in lower-motor neurogenic voiding dysfunction are analyzed. |
