Activation of Group-I mGluRs in the Superficial Extensor Muscle in Crayfish Tails Reduces EPSP Amplitude if the Preparation is not Pre-loaded with EGTA

Abstract

Attempting to better understand how memory and synaptic plasticity work, we examined the effect of activating group-I metabotropic glutamate receptors (mGluRs) on EPSP amplitude in normal crayfish superficial extensor muscle preparations and preparations with pre-loaded EGTA-AM. We measured EPSPs before and after adding DHPG (a group- I mGluR agonist) and compared the change in amplitude between the EGTA-AM crayfish and the non-EGTA-AM crayfish. Our findings support our hypothesis that group-I mGluRs induced a long-term depression (LTD) by increasing cytosolic calcium through the release of calcium from intracellular stores. DHPG caused a visible (though not statistically significant) decrease in EPSP amplitude, while the pre-loading of EGTA-AM diminished any effect that the DHPG had. These results suggest that some of the processes identified with the neural mechanisms of memory and learning in vertebrates are also present in crayfish.