GABA-immunoreactive neurons in the central and peripheral nervous system of the earthworm, Lumbricus terrestris (Oligochaeta, Annelida)

Abstract

The distribution of neurons immunoreactive for γ-aminobutyric acid was studied in the nervous system of Lumbricus terrestris (Oligochaeta). In the cerebral ganglion, the 86 cells immunoreactive for γ-aminobutyric acid represented 4.0% of the nerve cells in the brain, had a diameter of 12-50 µm, and were arranged in seven groups. Small-sized (18-30 µm) immunoreactive neurons occurred in the circumpharyngeal connectives. The axons of most immunoreactive neurons of the cerebral ganglion richly arborized in the ventral part of the neuropil and some could also be traced in the circumpharyngeal connectives. The subesophageal ganglion contained 94 immunoreactive cells (6.7% of the cells of this ganglion), also divided into seven groups, and with a diameter of 8-55 µm. The axons of the labeled neurons ran to the central neuropil giving both contra-and ipsilateral processes. Altogether 108 neurons in each ganglion (8.0% of their cells) of the ventral cord were immunopositive. Four labeled cell groups were present in the rostral and caudal part of each ganglion. Axons of these immunoreactive cells arborized in the central neuropil and projected to the segmental nerves. The stomatogastric ganglia and the enteric plexus also contained immunoreactive neurons. Many small elongated immunoreactive cells occurred in the gut epithelium. Postembedding immunogold electron microscopy revealed that immunoreactive varicosities mainly contained small pleomorphic (24 nm) agranular synaptic vesicles and some small granular (50 nm) vesicles.& k w d :

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

“…Whether the signal molecules represent differences in sensory processing and whether the different sensory functions are connected to the morphologically different sensory neurons remain to be determined. Our observations indicate that the distribution of GABA-IR sensory cells is similar to that observed in Lumbricus (Telkes et al 1996) and to those mentioned above. Moreover, our developmental studies seem to support the chemosensory function of these cells.…”

“…Ovoid or elongated GABA-IR sensory cells projected with short rodlike dendritic processes to the surface (Fig. 9), like those found in the foregut of Lumbricus (Telkes et al 1996). In some cases, the sensory dendrite could not be clearly distinguished from the cell body but was only represented by a small cytoplasmic protrusion.…”

Immunoreactivity to molluskan neuropeptides in the central and stomatogastric nervous systems of the earthworm, Lumbricus terrestris L.

“…Second, the axons of CNPL-IR cells form a rich network in the cerebral ganglia neuropil, whereas in the neuropil of the segmental ganglia, these IR elements are absent. Neither feature is typical of the neurons containing serotonin (Spörhase-Eichmann et al 1987a), octopamine , gammaaminobutyric acid (GABA; Telkes et al 1996), FMRFamide (Reglodi et al 1997b), corticotropin-releasing factor or urocortin (Lubics et al 2003).…”

“…Usually, immunocytochemical studies of the earthworm neurons refer to the normal pattern of staining with various antibodies (Spörhase-Eichmann et al 1987a,b;Telkes et al 1996;Reglodi et al 1997aReglodi et al ,b, 1999Lubics et al 1997Lubics et al , 2003. Alternatively, regenerationinduced changes have been traced (Banvolgyi et al 2000).…”

Evidence for the presence of thyroid stimulating hormone, thyroglobulin and their receptors in Eisenia fetida: a multilevel hormonal interface between the nervous system and the peripheral tissues

“…serotonin: Ehinger and Myhrberg 1971;Lengvári et al 1992;Rude 1969;Spörhase-Eichmann et al 1987a,b;octopamine: Csoknya et al 1996;Robertson 1975), amino acids and peptides (e.g. GABA: Telkes et al 1996; Eisenia-tetradecapeptide: Csoknya et al 2000;Ukena et al 1997;FMRFamide: Reglődi et al 1997) but some hormone-secreting cells are also known (corticotropin-releasing factor: Lubics et al 2003;gastrointestinal hormones: Reglődi et al 1999;Remy et al 1982;ACTH: Aros et al 1980;Kaloustin 1986). According to our double-staining experiments, all of the TSH-LI neurons in the CNS co-localize GABA.…”