Double-label immunocytochemistry was used to investigate the
colocalisation of various neuropeptides and the enzymes nitric oxide
synthase (NOS) and tyrosine hydroxylase (TH) in intramural ganglia of
the human male urinary bladder neck and trigone. Postmortem specimens
were obtained from 7 male infants and children ranging in age from 2 mo
to 3 y who had died as a result of cot death or accidental trauma. On
average 60% of the intramural neurons were non-TH-immunoreactive (-IR)
(i.e. presumptive cholinergic) and 40% were TH- and DbβH-IR (i.e.
noradrenergic). Within the non-TH-IR population, calcitonin gene-related peptide (CGRP) was found in 65% of cells, neuropeptide Y (NPY)
in 90%, nitric oxide synthase (NOS) in 45%, somatostatin (SOM) in 90%,
and vasoactive intestinal polypeptide (VIP) in 40%. The corresponding
values for the TH-IR neurons were CGRP (54%), NPY (70%), NOS (58%), SOM
(73%) and VIP (40%). All the observed bombesin (BOM)-immunoreactivity
was colocalised with TH while 90% of VIP and almost all the CGRP was
colocalised with NPY. Less than 5% of neurons were immunoreactive for
substance P (SP) or met-enkephalin (m-ENK) and some of these also
contained TH. Varicose nerve fibres were seen in close proximity to
some of the intramural neurons, the majority of such varicosities
showing immunoreactivity to CGRP, VIP or TH. Less common were
pericellular varicosities immunoreactive to NPY, SOM or SP. These
results demonstrate the neurochemical heterogeneity of intramural
neurons in the human bladder neck and provide indirect evidence for the
complexity of the peripheral innervation of the human urinary
bladder.