Neuromuscular transmitter candidates of a centipede (Lithobius forficatus, Chilopoda)

Abstract

BackgroundThe neuromuscular junction is the chemical synapse where motor neurons communicate with skeletal muscle fibers. Whereas vertebrates and many invertebrates use acetylcholine as transmitter at the neuromuscular junction, in those arthropods examined up to now, glutamate and GABA are used instead. With respect to taxon sampling in a phylogenetic context, there is, however, only a limited amount of data available, focusing mainly on crustaceans and hexapods, and neglecting other, arthropod groups. Here we investigate the neurotransmitter equipment of neuromuscular synapses of a myriapod, Lithobius forficatus, using immunofluorescence and histochemical staining methods.ResultsGlutamate and GABA could be found colocalised with synapsin in synaptic boutons of body wall and leg muscles of Lithobius forficatus. Acetylcholinesterase activity as a marker for cholinergic synapses was found abundantly in the central nervous system and also in some peripheral nerves, but not at neuromuscular junctions. Furthermore, a large number of leg sensory neurons displayed GABA-immunofluorescence and was also labeled with an antiserum against the GABA-synthesizing enzyme, glutamate decarboxylase.ConclusionsOur data indicate that glutamate and GABA are neurotransmitters at Lithobius forficatus neuromuscular junctions, whereas acetylcholine is very unlikely to play a role here. This is in line with the concept of glutamate as excitatory and GABA as the main inhibitory neuromuscular transmitters in euarthropods. Furthermore, we have, to our knowledge for the first time, localized GABA in euarthropod leg sensory neurons, indicating the possibility that neurotransmitter panel in arthropod sensory systems may be far more extensive than hitherto assumed.

Mushroom bodies in crustaceans: Insect‐like organization in the caridid shrimp Lebbeus groenlandicus

“…Primary antibody was then added to the solution and left overnight at RT on a gentle shake. No demasking step was required for GAD immunolabeling in L. groenlandicus , as has been reported in previous studies (Langeloh, Wasser, Richter, Bicker, & Stern, ; Stemme et al, ).…”

FKN/NR Signaling Pathway Regulates Hippocampal Inflammatory Responses: the Survival of Hippocampal Neurons in Diabetic Rats with Chronic Unpredictable Mild Stress

“…Therefore, the inflammatory factors are elevated under a DD state, whereas the CX3CR1 pathway may improve their levels. Glu is an excitatory neurotransmitter that plays an important role in maintaining the normal functional activities of the central nervous system and in regulating nerves [ 34 ]. However, high-concentration glutamate has neurotoxic effects and can damage neurons and thus induce neuropsychiatric diseases [ 35 ].…”

The Insecticidal Activity of Rhinella schneideri (Werner, 1894) Paratoid Secretion in Nauphoeta cinerea Cocroaches

“…The invertebrate neuromuscular junction differs from vertebrates by using glutamate and GABA as excitatory and inhibitory neurotransmitters, respectively, instead of ACh [ 30 ]. From the anatomical point of view, a number of GABAergic interneurons departs from segmental ganglia from ventral nerve cord [ 31 ]. The physiological modulation of the insect skeletal muscle also involves the innervations through octopaminergic/tyraminergic (OA/TA) neurons, which receive direct inputs from the dorsal unpaired median neurons (DUM) and the ventral unpaired median neurons (VUM), respectively [ 32 , 33 , 34 ].…”

“…Thereby, this later information may indicate that the neuromuscular blockade induced by RSPS involves the modulation of the octopaminergic pathways, by the activation of DUM neurons and a consequent GABAergic modulation at neuromuscular junctions. However, it is worth noting that both ACh and GABA also seem to be classical neurotransmitters in mechanosensory neurons [ 31 ]. Thus, the increase in firing rates induced by RSPS in leg sensilla could be, at least in part, associated with an anti-AChE activity, but could also be another clue of the increase in GABAergic signaling in peripheral nerves.…”