Excitatory neurotransmitters in the tentacle flexor muscles responsible for space positioning of the snail olfactory organ

Abstract

and increasing those of M3. In both cases, the modulation site was presynaptic. Serotonin (5-HT) at high concentration (10 -5 M) increased the amplitude of both the nerve-and the ACh-evoked contractions in all muscles. The relaxation rate was facilitated suggesting pre-and postsynaptic site of action. Our data provided evidence for a DAergic and 5-HTergic modulation of cholinergic nerves innervating flexor muscles of the tentacles as well as the muscles itself. These effects of DA and 5-HT may contribute to the regulation of sophisticated movements of tentacle muscles lacking inhibitory innervation.

Regional adaptation defines sensitivity to future ocean acidification

“…Furthermore, in marine molluscs, homarine and branched chain amino acids (such as leucine and valine) also underpin processes related to acid–base balance and immune function that are intertwined with energy metabolism. In comparison, glutamate has been highlighted as a possible excitatory neurotransmitter in molluscs22. Thus, our data suggest that compared with more southerly populations, subpolar snails significantly upregulate a host of physiological systems, including metabolism and acid–base balance and immune and neurological function to help maintain homeostasis.…”

Nicotinic Acetylcholine Receptors Containing the α7-Like Subunit Mediate Contractions of Muscles Responsible for Space Positioning of the Snail, Helix pomatia L. Tentacle

“…Scanning of the environment by protracted tentacles, and twitching and quivering movements performed during olfactory orientation, are primarily due to the contraction of three FMs: M1, M2 and M3. The ACh effect is comparable to that elicited by electrical nerve stimulation and both responses are effectively attenuated by cholinergic antagonists [34] . It is suggested therefore that contraction evoked by the excitatory neurotransmitter ACh is due to agonist binding at specific membrane receptors, resulting in the opening of cationic (mainly Na + ) channels, which in turn stimulates the Na-Ca exchange mechanism, thereby increasing the concentration of cytosolic Ca 2+ entering from the extracellular space [35] .…”

“…The effect of ACh on FMs of the superior tentacles was a slow and consistent tonic, concentration-dependent contracture with no phasic activity. The threshold for the depolarizing effect of ACh was between 10 −8 and 10 −7 M while the maximum response was observed between 10 −4 –10 −3 M. The effective concentration of the ACh (EC 50 = 7×10 −6 M see [34] to induce contraction is sufficiently low to provide compelling evidence that ACh is an excitatory neurotransmitter at the neuromuscular contacts of FMs. At concentrations producing maximum contraction (10 −4 M), repeated ACh application did not lead to a reduction in size of the response, demonstrating slow desensitization properties of the muscle AChRs ( Fig.…”

Anatomical and physiological background permitting spatial odor sensation in stylommatophoran molluscs

“…The tentacle of the slug Vaginula revealed two types of nerve endings both containing clear synaptic vesicles accompanied by granular vesicles [4]. In the FM co-localization and co-transmission of ACh and Glu have not been proven, however, it was observed that Glu evokes fast, while ACh evokes slow muscle contractions and the presence of both transmitters were demonstrated immunohistochemically [57]. Thus the dual excitatory innervation may contribute to the fine-tuning of contractions and force produced by the FMs needed for the complex tentacular movements during olfactory orientation.…”

“…Polyneuronal innervation is important when muscle fibers do not generate propagated action potentials and activity of several motoneurons is necessary to induce full mechanical response. Another benefit of polyneuronal innervation is the possibility to release more than one excitatory transmitter and modulatory substances permitting fine regulation of the muscle [57]. Dual, AChergic and Gluergic excitatory innervation is not unique in the animal kingdom.…”