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Neuroreport. 2002 Dec 3;13(17):2235-9.

Effects of glutamate agonists on the isolated neurons from the locomotor network of the mollusc Clione limacina.

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A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russia.


In the pteropod mollusc, locomotor rhythm is produced by the central pattern generator (CPG), mainly by the reciprocal activity of interneurons, groups 7 and 8, which are active in the phases of the dorsal and ventral flexion of the wings, respectively. Both groups produce excitation in the CPG neurons controlling the same phase of the locomotor cycle, and inhibition in the neurons of the opposite phase. As previously suggested, the connections of the group 7 interneurons to the follower CPG neurons are glutamatergic. However, the properties of the glutamatergic receptors in the postsynaptic cells are unknown. In this work, the identified CPG motoneurons of the antagonistic groups 1 and 2 were isolated from the CNS, and their responses to the local application of glutamate agonists were examined. Glutamate elicited opposite effects in the neurons of these two groups, reproducing excitatory and inhibitory influence of the group 7 interneurons. Interestingly, micromolar concentrations of glutamate agonists kainate, domoate and AMPA elicited excitation in both types of the motoneurons. To test for the possible of the NMDA receptors, NMDA was applied, as well as an equimolar mixture of NMDA and glycine. The isolated motoneurons showed excitatory response to these applications only at high (millimolar) concentrations. These results suggest that the motoneurons of group 1 possess excitatory glutamate receptors and that motoneurons of group 2 may posses a composite population of receptors, which are responsible for the inhibitory action of glutamate and excitatory action of its AMPA/kainate agonists.

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