An investigation into signal transduction mechanisms involved in DHPG-induced LTD in the CA1 region of the hippocampus.

Previously, we have found that activation of mGlu receptors using a group I-specific mGlu receptor agonist, (RS)-3,5-DHPG, can induce long-term depression (LTD) in the CA1 region of the hippocampus and that, once established, this synaptic depression can be reversed by application of the mGlu receptor antagonist, (S)-MCPG [Palmer et al., 1997. Neuropharmacology 36, 1517-1532]. We have started to investigate the signal transduction mechanisms involved in these effects. Group I mGlu receptors couple to phospholipase C and therefore can activate protein kinase C and mobilise Ca2+ from intracellular stores. However, neither protein kinase C inhibitors (chelerythrine or Ro 31-8220) nor agents which deplete intracellular Ca2+ stores (thapsigargin or cyclopiazonic acid) were able to prevent DHPG-induced LTD. Furthermore, the ability of MCPG to reverse DHPG-induced LTD was not prevented by these compounds. These results suggest that it is unlikely that DHPG-induced LTD, or its reversal by MCPG, is produced via activation of either protein kinase C or by release of Ca2+ from intracellular stores.