No abstract

The distribution and patterns of colocalization of nitric oxide synthase (NOS), vasoactive intestinal peptide (VIP), neuropeptide Y (NPY) and the catecholamine-synthesizing enzyme tyrosine hydroxylase (TH) were examined in nerve fibers supplying the human lower ureter using double label immunofluorescence. Many nerve fibers immunoreactive for NOS were observed within the ureter. Positive varicose fibers were seen running longitudinally within the smooth muscle bundles, particularly those of the inner layers of the ureter. Immunoreactive axons were also prominent within the subepithelium, and as plexi surrounding many blood vessels. The colocalization studies indicated that NOS was never present in presumptive sympathetic nerve fibers expressing TH. All fibers containing VIP, however, were also immunoreactive for NOS. In addition, a minor population of NOS fibers did not contain VIP. Neuropeptide Y coexisted with NOS in a significant number of nerve terminals, although fibers expressing only NPY were equally common. Several immunochemically distinct nerve populations can therefore be distinguished in the human ureter: (1) nerves containing NOS either with or without VIP; (2) NOS-immunoreactive fibers with NPY; and (3) those fibers expressing TH or NPY which do not contain NOS. The results indicate that some non-noradrenergic peptide-containing nerves in the human ureter have the capacity to synthesize nitric oxide (NO), and that NO may be involved in the regulation of ureteric motility.

The expression of neuropeptides, and the enzymes nitric oxide synthase and tyrosine hydroxylase were examined in intramural ganglia of human urinary bladder using single label immunocytochemistry. Scattered ganglia composed of between 1-36 neurons (median 4) were observed in all layers of the lateral wall of the bladder. These contained immunoreactivity to vasoactive intestinal peptide, nitric oxide synthase, neuropeptide Y, and galanin. Neurons within the bladder were heterogeneous with regard to their content of these antigens, with the proportion of immunopositive cells ranging from 58-84%. Occasional neurons with immunoreactivity to the catecholamine-synthesizing enzyme, tyrosine hydroxylase, were also observed. No cell somata, however, were immunoreactive for enkephalin, substance P, calcitonin gene-related peptide or somatostatin. Varicose terminals entering the ganglia were seen to form pericellular baskets surrounding some of the principal ganglion cells. The most prominent pericellular varicosities were those containing calcitonin gene-related peptide- or vasoactive intestinal peptide-immunoreactivity, followed by those with immunoreactivity for enkephalin, neuropeptide Y, or galanin. Less common were pericellular varicosities with substance P-immunoreactivity, which may represent collateral processes of unmyelinated primary sensory fibres, and presumptive noradrenergic processes containing tyrosine hydroxylase. Some calcitonin gene-related peptide-immunoreactive varicosities constituted a distinct type, terminating as large pericellular boutons 2-4 microns in diameter. Fibres containing nitric oxide synthase- or somatostatin-immunoreactivity were not associated with the intramural neurons. The results demonstrate that intrinsic neurons within the human urinary bladder express a number of neuroactive chemicals, and could in principle form circuits with the potential to support integrative activity.