Mária Csoknya

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

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 submuscularis is composed of nerve fibres only, whereas the plexus subepithelialis 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-HT3 and GABAB 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.

Octopamine in the central nervous system of Oligochaeta: an immunocytochemical and biochemical study

Abstract.The distribution of octopamine (OA)-like immunoreactive neurons was investigated, and the concentration of OA was assayed by high-performance liquid chromatography in the central nervous system of Oligochaeta species, Lumbricus terrestris, Eisenia fetida, and Lumbricus polyphemus. OA-like immunoreactive nerve cells were found in all parts of the central nervous system; certain regions of the neuropil of the ganglia were densely innervated by immunoreactive fibers. Altogether 96–102 OA-like immunoreactive neurons were detected in the cerebral ganglion, 18 in the subesophageal ganglion, and 14 in the segmental ganglia of 2nd–5th and 40th–45th body segments of Lumbricus terrestris; the relevant numbers of neurons in Eisenia were 88–98, 20–22, and 6, respectively. The sizes of OA immunoreactive-like cells showed great variability according to their anatomical localization. High-performance liquid chromatography assay revealed the presence of OA in each investigated part of the central nervous system, showing concentration values between 8.6 and 16.7 pmol/mg wet weight in the three species. The concentration of the OA precursor tyramine was significantly lower in the central nervous system of Eisenia (<0.5 pmol/mg wet weight) than in that of both Lumbricus species (0.67–2.0 pmol/mg wet weight). The metabolism of 3H-tyrosine revealed that tyramine and OA were synthesized by the enzymes tyrosine-decarboxylase and tyramine-β-hydroxylase, respectively. Thus, OA appears to have a regulatory role in the central nervous system of Oligochaeta.

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

Organization of the serotonergic system and changes of the serotonin (5‐HT) content were studied during the embryogenesis of the earthworm Eisenia fetida, using immunocytochemistry and HPLC. A gradual emergence of 5‐HT immunoreactive (IR) cells and their axon projections in the several ganglia of the central (CNS) and peripheral nervous system are described in the context of a staged time‐scale of development. The first 5‐HT‐IR neurons appear in the subesophageal ganglion at an early embryonic stage (E2), followed by neurons in some rostrally located ventral ganglia. In the cerebral ganglion, 5‐HT‐IR cells can be detected only from stage E5. The number of labeled cells in each ganglion of the embryo increases until hatching, when it is still considerably lower than that observed in adults. This shows that the development of the 5‐HTergic system is far from complete by the end of embryogenesis. Organization of 5‐HT‐IR innervation of the body wall starts by stages E3 to E4. In the stomatogastric nervous system the first 5‐HT‐IR fibers can be detected by stage E5. By stage E9 5‐HT immunopositive neurons can be observed in both the stomatogastric ganglia and the enteric plexus. Both 5‐HT levels and the numbers of the labeled cells show a significant increase before hatching, which indicate a functional maturation of the 5‐HTergic system. Based on the early appearance of 5‐HT, we suppose that it may play a regulatory role in both the gangliogenesis and the maturation of peripheral functions necessary during postembryonic life. J. Comp. Neurol. 497:451–467, 2006.

Glial cells in the central nervous system of earthworm, EISEnIA fEtIDA *

Glial elements in the central nervous system of Eisenia fetida were studied at light- and electron microscopic level. Cells were characterized with the aid of toluidine blue, Glial Fibrillary Acidic Protein (GFAP), S100 staining. We identified neurilemmal-, subneurilemmal-, supporting-nutrifying- and myelinsheath forming glial cells. Both neuronal and non-neuronal elements are S100-immunoreactive in the CNS. Among glial cells neurilemmal and subneurilemmal cells are S100-immunopositive. With the antibody against the S100 protein one band is visible at 15 kDa. GFA P-immunopositive supporting-nutrifying glial cells are localized around neurons and they often appear as cells with many vacuoles. GFA P-positive cell bodies of elongated neurilemmal glial cells are also visible. Western blot analysis shows a single 57 kDa GFA P immunoreactive band in the Eisenia sample. At ultrastructural level contacts between neuronal and glial cells are recognizable. Glial cell bodies and their filopodia contain a granular and vesicular system. Close contacts between neuronal cell membranes and glial filopodia create a special environment for material transport. Vesicles budding off glial cell granules move towards the cell membranes, probably emptying their content with kiss and run exocytosis. The secreted compounds in return may help neuronal survival, provide nutrition, and filopodia may also support neuronal terminals.