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

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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). J. Comp. Neurol. 461:350–361, 2003.
Funding Information
  • Spanish Science and Technology Ministry (BXX2000-0453-C02-01, BXX2000-0453-C02-02)
  • Xunta de Galicia (PGIDT99BIO20002)