Effects of metabotropic glutamate receptor activation on the cellular and network level in the lamprey spinal cord

The effects of the metabotropic glutamate receptor (mGluR) agonist ACPD ((lS,3R)-l-aminocyclopen- tane-l,3-dicarboxylic acid) on single neurones and on the network underlying locomotion in the lamprey have been analysed. ACPD induces a depolarization in lamprey spinal cord neurones, which is insensitive to tetrodotoxin (TTX) and ionotropic glutamate receptor antagonists, but is reversibly blocked by the mGluR antagonist MCPG ((+)- alpha-methyl-4-carboxyphenylglycine). The ACPD- induced depolarization persists in a calcium-free solution or when the calcium channel blocker cadmium is added to the solution. At the network level ACPD causes an increased burst frequency during fictive locomotion by increasing the excitability level of network neurones.