Immunohistochemical study of the nervous system in earthworm (Lumbricus terrestris L.)

In the present work it we describe serotonin, noradrenaline, proctolin, neuropeptide Y, substance P, and calcitonin gene related peptide immunoreactive structures in earthworm. A few large serotonin immunoreactive perikarya are located in brain and in the stomatogasric ganglia and many of them in the segmental ganglia. A serotonin immunoreactive fiber plexus can be seen beneath the epithelium of the body wall, both the sensory papillae and chaetae contain serotonin immunoreactive elements. Some of the sensory cells are serotonin immunoreactive, too. A serotonin immunoreactive network can ben found in the enteric network of the fore- and mid-gut. Only a few noradrenaline immunoreactive cells are observed in the caudal part of the brain, while their number in the segmental ganglia is high. Proctolin-, and substance P immunoreactive cells are small and numerous in the brain without any preference in their location. Such nerve cells are widely distributed in the ganglia of the stomatogastric system, in the subesophageal and in segmental ganglia. Many surface epithelial (probably sensory) cells are proctolin immunoreactive. Substance P immunoreactive nerve cells can also be located in the entire length of the enteric plexus together with substance P immunoreactive fibers. No neuropeptide Y- or calcitonin gene related peptide immunoreactive structures can be seen in the brain. A relative small number of neuropeptide Y- and calcitonin gene related peptide immunoreactive perikarya, and a rich network of neuropeptide Y- and calcitonin gene related peptide immunoreactive fibers can be detected in the subesophageal ganglion. According to preliminary studies, neuropeptide Y is probably co-localized with serotonin.