Interaction between metabotropic and ionotropic glutamate receptors regulates neuronal network activity.
Experimental and computational techniques have been used to investigate the group I metabotropic glutamate receptor (mGluR)-mediated increase in the frequency of spinal cord network activity underlying locomotion in the lamprey. Group I mGluR activation potentiated the amplitude of NMDA-induced currents in identified motoneurons and crossed caudally projecting network interneurons. Group I mGluRs also potentiated NMDA-induced calcium responses. This effect was blocked by a group I mGluR-specific antagonist, but not by blockers of protein kinase A, C, or G. The effect of group I mGluRs activation was also tested on NMDA-induced oscillations known to occur during fictive locomotion. Activation of these receptors increased the duration of the plateau phase and decreased the duration of the hyperpolarizing phase. These effects were blocked by a group I mGluR antagonist. To determine its role in the modulation of NMDA-induced oscillations and the locomotor burst frequency, the potentiation of NMDA receptors by mGluRs was simulated using computational techniques. Simulating the interaction between these receptors reproduced the modulation of the plateau and hyperpolarized phases of NMDA-induced oscillations, and the increase in the frequency of the locomotor rhythm. Our results thus show a postsynaptic interaction between group I mGluRs and NMDA receptors in lamprey spinal cord neurons, which can account for the regulation of the locomotor network output by mGluRs.
Krieger
P
P
Nobel Institute for Neurophysiology, Department of Neuroscience, Karolinska Institute, S-171 77 Stockholm, Sweden. Patrik.Krieger@neuro.ki.se
Hellgren-Kotaleski
J
J
Kettunen
P
P
El Manira
A J
AJ
D000818:Animals; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003198:Computer Simulation; D019204:GTP-Binding Proteins / Q000378:metabolism; D007798:Lampreys; D008124:Locomotion / Q000187:drug effects / Q000502:physiology; D008734:Methoxyhydroxyphenylglycol / Q000031:analogs & derivatives* / Q000494:pharmacology; D016202:N-Methylaspartate / Q000378:metabolism / Q000494:pharmacology; D009415:Nerve Net / Q000378:metabolism*; D016571:Neural Networks, Computer; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D047428:Protein Kinase Inhibitors; D018091:Receptors, AMPA / Q000378:metabolism*; D018092:Kainic Acid Receptors / Q000378:metabolism*; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D012433:Ryanodine / Q000494:pharmacology; D013116:Spinal Cord / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects
D002118:Calcium; D019204:GTP-Binding Proteins; D008734:Methoxyhydroxyphenylglycol; D016202:N-Methylaspartate; D047428:Protein Kinase Inhibitors; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D018094:Receptors, Metabotropic Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D012433:Ryanodine; C104077:metabotropic glutamate receptor type 1; C010117:3,4-dihydroxyphenylglycol