LONG-term potentiation (LTP) and long-term depression (LTD), often use
d as essential components in synaptic models for learning, memory and
forgetting, can be produced in cortical tissue by repetitive activatio
n of neural pathways under different stimulus conditions. The involvem
ent of metabotropic glutamate receptors (mGluRs) has been postulated t
o be necessary for the establishment of either or both forms of synapt
ic plasticity in hippocampus. The recent introduction of a specific an
tagonist for mGluRs, (+/-)-alpha-methyl-4-carboxyphenl-glycine, prompt
ed the investigation of the respective involvement of this receptor po
pulation in the induction of LTP and LTD in visual cortex of the rat i
n vitro. The results suggest the critical involvement of mGluRs in pro
ducing LTD but not LTP.