H. Uemura et al., IMMUNOHISTOCHEMICAL INVESTIGATION OF NEUROPEPTIDES IN THE CENTRAL-NERVOUS-SYSTEM OF THE AMPHIOXUS, BRANCHIOSTOMA-BELCHERI, Cell and tissue research, 277(2), 1994, pp. 279-287
The immunohistochemical localization of nine different neuropeptides w
as studied in the central nervous system of the amphioxus, Branchiosto
ma belcheri. In the brain, perikarya immunoreactive for urotensin I an
d FMRFamide were localized in the vicinity of the central canal. One o
f the processes of each of these perikarya was found to cross the dors
oventral slit-like lumen of the central canal. Oxytocin-immunoreactive
short fibers, but not perikarya, were detected in the ventral part of
the brain. Perikarya immunoreactive for arginine vasopressin/vasotoci
n, oxytocin and FMRFamide were widely distributed in the spinal cord.
Arginine vasopressin/vasotocin-immunoreactive fibers often made contac
ts with Rohde cell axons. Angiotensin II-immunoreactive perikarya were
observed in the posterior half of the spinal cord, and urotensin I-im
munoreactive perikarya were found in the caudal region of the spinal c
ord. Cholecystokinin/gastrin-immunoreactive fibers, but not perikarya,
were detected in the spinal cord; some extended as far as the ependym
al layer of the cerebral ventricle. No colocalization of the peptides
examined was observed. No immunoreactivity for atrial and brain natriu
retic peptides nor for urotensin II was detected. The present study in
dicates that there are at least six separate neuronal systems that con
tain different peptides, respectively, in the central nervous system o
f the amphioxus. Their functions remain to be determined.