Adrenergic innervation of the urinary bladder body in the cat with special reference to structure of the detrusor muscle: an immunohistochemical study of noradrenaline and its synthesizing enzymes.

The distribution of adrenergic nerves in the body detrusor muscle of the cat urinary bladder was studied by means of the immunohistochemical identification of noradrenaline (NA) and the NA synthesizing enzymes tyrosine hydroxylase, aromatic L-aminoacid decarboxylase and dopamine beta-hydroxylase. We identified the basic structural organization of the detrusor muscle, which had previously been described as lacking discernible layers. In the lateral wall, both outer longitudinal and inner circular muscle bundles were present, the latter extending in both anterior and posterior directions. The posteriorly running bundles came to lie on the outside of the posterior wall where they enabled recognition of inner longitudinal muscle bundles. Those running anteriorly were dispersed to enter the longitudinal bundles in the anterior wall. NA-immunoreactive nerve fibers in the detrusor muscle of the bladder were found to be similar to those immunoreactive for NA synthesizing enzymes in both distribution and density. In the upper and middle bladder body--including the dome (apex)--immunoreactive nerve fibers were always more abundant in the outer part of the detrusor muscle than in the inner part, regardless of the course of muscle bundles. Even in individual muscle bundles running from the inside to the outer surface, the outer part was more richly innervated by immunoreactive fibers than the inner part. In the bladder dome, a moderate number of immunoreactive nerve fibers preferentially innervated the outer part of the muscle layer. In the lower bladder body, these nerve fibers increased in density in the inner part of the detrusor muscle. There was no sexual difference in density or distribution of nerve fibers. NA- and NA synthesizing enzyme-immunoreactive nerve fibers were markedly decreased in number after 6-hydroxydopamine treatment. No dopamine- or phenylethanolamine-N-methyltransferase-immunoreactive nerve fibers were present in the bladder. The findings of this study indicate that the cat bladder musculature includes longitudinal and circular muscle bundles, both of which are extensively innervated by adrenergic nerves, particularly in the outer part of the bladder.