Distribution of neuropeptide Y immunoreactivity in the central and peripheral nervous systems of amphioxus (Branchiostoma lanceolatum Pallas)

Abstract

Immunocytochemistry techniques were employed to investigate the distribution of neuropeptide Y-like-immunoreactive (NPY-ir) cells and fibers in the central and peripheral nervous systems of adult amphioxus. NPY-ir neurons of the commissural type were abundant in the brain and present but more scarce in the spinal cord. These neurons gave rise to conspicuous NPY-ir tracts that coursed along the entire length of the nerve cord. Some fibers exhibited conspicuous Herring body-like swellings. In the peripheral nervous system, small NPY-ir neurons and a large number of thin, beaded NPY-ir fibers were observed in the atrial region, indicating the involvement of this substance in visceral regulation. A few NPY-ir fibers, possibly afferent to the spinal cord, coursed in the ventral branches of the spinal nerves of this region, whereas no NPY-ir fibers coursed in the preoral or velar nerves or in the dorsal branches of the other spinal nerves. These results indicate that NPY is widely used as a neuroregulator/neurotransmitter in the central and peripheral nervous systems of this primitive chordate. In addition, this study demonstrates the presence of tall, thin NPY-ir cells in the putative adenohypophyseal homologue, the Hatschek's pit organ, which is located in the roof of the preoral cavity (vestibule).

Sensory Systems in Amphioxus: A Window on the Ancestral Chordate Condition

“…that it was present in basal metazoans as indicated by the presence of Pitx homologs [Jacobs and Gates, 2003], and served as a non-neural solution to the problem of modulating the function of internal organ systems in response to externally received stimuli. It also helps explain the presence of neuropeptides involved in metabolic control among the secretions of the preoral pit [Castro et al, 2003]. …”

Neuronal organization of the brain in the adult amphioxus (Branchiostoma lanceolatum): A study with acetylated tubulin immunohistochemistry

“…In teleosts, most FMRF-ir cells were located in the forebrain and were mostly absent in the spinal cord (Bonn and K€ onig, 1989;Castro et al, 2001). With regard to NPY, most NPY-ir translumenal neurons of the amphioxus brain (Castro et al, 2003) were caudal to the lamellate cells (i.e., located in the putative rhombencephalon homologue), and they included isolated large, spindle-shaped and triangular neurons and groups of small cells. In lampreys and teleosts, some groups of NPY-ir neurons are found in the brain, including the rhombencephalon (see Castro et al, 1999;Barreiro-Iglesias et al, 2010).…”

“…The specificity of the immunostaining in amphioxus was tested by preabsorption of the primary antiserum diluted 1:3,000 in PBS with synthetic porcine NPY (Sigma; 4 lM). These controls completely abolished the immunoreaction in the amphioxus nervous system (Castro et al, 2003).…”

“…The NPY antibody has been used in a study of amphioxus (Castro et al, 2003), and also in some vertebrates including lampreys (Barreiro-Iglesias et al, 2010). The antiserum shows no cross-reactivity in dot blot with substance P, neurokinin A, neurokinin B, vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP, rat), calcitonin and somatostatin conjugated to BSA, or BSA.…”

“…GA1159, RRID: AB_2314445; dilution 1/1,000; for details see Anad on et al, 1998), NPY (Castro et al, 2003), and CR (Castro et al, 2004) were used for comparison. We also used paraffin series of transverse sections of formalin-fixed amphioxus that were stained with a silver impregnation method (Holmes, 1953).…”