Neurochemical characterization of nervous elements innervating the body wall of earthworms (Lumbricus, Eisenia): immunohistochemical and pharmacological studies

Abstract

The distribution and chemical neuroanatomy of nervous elements and certain pharmacological-physiological characteristics of the innervation of the body wall in earthworms are described. Solitary sensory bipolar cells can be found among the epithelial cells. These bipolar cells contain serotonin, tyrosine hydroxylase, histamine, gamma-amino-butyric acid (GABA), Eisenia tetradecapeptide, proctolin or rhodopsin in various combinations. In the body wall, the plexus sub-muscularis is composed of nerve fibres only, whereas the plexus sub-epithelialis and muscularis also contain solitary nerve cells. These cells display histamine, GABA or neuropeptide Y immunoreactivity. The fibres of the three plexuses are reactive to serotonin, histamine, Eisenia tetradecapeptide, proctolin, GABA and neuropeptide Y antibodies. FMRFamide-immunoreactive fibres of the plexus muscularis originate from the central nervous system, whereas axons containing the other studied molecules are derived from both peripheral and central structures. High pressure liquid chromatography assays have revealed serotonin, dopamine and histamine in the body wall. Contractions of the body wall musculature can be elicited with serotonin and FMRFamide. Serotonin-evoked contractions are suppressed by the application of GABA. Serotonin acts both directly on the muscle cell receptors and indirectly through initiating transmitter release from the nervous elements, whereas the FMRFamide-induced contractions seem to be mediated through the muscle cell receptors only. The pharmacological profiles of the serotonin and GABA receptors resemble those of the vertebrate 5-HT(3) and GABA(B) receptor types. Our findings indicate that both the sensory and efferent system of the annelid body wall operate by means of a variety of neuroactive compounds, suggesting a complex role of signalling systems in the regulation of this organ.

Extensive presence of serotonergic cells and fibers in the peripheral nervous system of lampreys

“…The presence of serotonergic structures in the musculature has principally been reported in invertebrates, including nematodes (Dernovici et al,2007), cycliophora (Wanninger,2005), entoprocta (Fuchs et al,2006), platyhelminths (Stewart et al,2003; Sebelova et al,2004), annelids (Reglödi et al,1997; Csoknya et al,2005), and mollusks (Faccioni‐Heuser et al,2004). In these invertebrates the number of serotonergic peripheral neurons far exceeds those found in the central nervous system (Faccioni‐Heuser,2004).…”

A review of FMRFamide- and RFamide-like peptides in metazoa

“…In polychaetes, immunoreactivity for FMRFa has been found in the oesophageal muscles and gut of Nereis virens, and a FLP is likely to regulate gut activity (Krajniak and Greenberg 1992). There is evidence for FMRFa-like immunoreactive nerve fibres, which occur in the muscular plexus of the body wall of oligochaetes, and FMRFa directly excites the body wall muscle since its effect persists in the presence of tetrodotoxin (Csoknya et al 2005). Interestingly, FMRFalike immunoreactivity has been found in sensory neurones in Lumbricus terrestris body wall epithelium, indicating a sensory role for FLPs in oligochaetes ).…”

Embryogenesis of the serotonergic system in the earthworm Eisenia fetida (Annelida, Oligochaeta): Immunohistochemical and biochemical studies

“…This type of movements begins before the embryonic NS becomes functionally mature (Stent et al, 1992). 5-HT has been described as a modulator of the contraction of the muscle layers in the body wall of adult earthworm (Gardner, 1976;Gardner and Walker, 1982;Ukena et al, 1995;Boyle and Yoshino, 2005;Csoknya et al, 2005;Wakabayashi et al 2005). The 5-HT-IR innervation of the body wall through the segmental nerves was detected by stages E3-E4 in Eisenia fetida.…”