The occurrence and distribution of neuropeptide-containing nerve
fibres in the human circumvallate papillae
were examined by the peroxidase–antiperoxidase immunolocalisation
method using surgical specimens that
had not been subjected to radiotherapy, and the abundance of
neuropeptide-containing fibres was expressed
as the percentage of total nerve fibres demonstrated by protein gene product
(PGP) 9.5 immunoreactivity for
a quantitative representation of these peptidergic fibres. Substance
P (SP) and calcitonin gene-related peptide
(CGRP) immunoreactive (IR) nerve fibres were densely distributed in
the connective tissue core of the
circumvallate papillae, and some SP and CGRP-IR fibres were associated
with the taste buds. A moderate
number of vasoactive intestinal polypeptide (VIP)-IR fibres and
a few galanin (GAL)-IR fibres were also
seen in the connective tissue core and subepithelial layer. There
were, however, no VIP-IR or GAL-IR fibres
associated with the taste buds. Neuropeptide Y (NPY)-IR fibres were
few and were associated with the
blood vessels. Within the epithelium of the circumvallate papillae,
no peptidergic fibres were found, although
a number of PGP 9.5-IR fibres were detected. The abundance of SP, CGRP,
VIP, and GAL-IR fibres
expressed as the percentage of total PGP 9.5 IR fibres was
25.35±3.45%, 22.18±3.26%, 10.23±1.18%,
and 4.12±1.05%, respectively. The percentage of NPY-IR
fibres was below 3%. In a deeper layer of the
papillae, a few VIP, GAL, and NPY-IR ganglion cells were found,
and VIP immunoreactivity was detected
in a few cells of the taste buds. There was no somatostatin,
leucine enkephalin, or methionine enkephalin
immunoreactivity in the circumvallate papillae. These results
suggest that the dense SP and CGRP-IR fibres
within the connective tissue core of the human circumvallate papillae
may be involved in the deep sensation of the tongue.