Modulation by metabotropic glutamate receptor of long-term potentiation of population spikes in the dentate gyrus in vivo.

The effect of 2-amino-3-phosphonopropionate (AP3), a metabotropic glutamate receptor antagonist, on long-term potentiation (LTP) of evoked potentials in the dentate gyrus was investigated using anesthetized rats. Intracerebroventricular injection of AP3 (50 nmol) prior to application of tetanic stimulation did not significantly affect LTP induced by 100-pulse, 100-Hz tetanus, but inhibited the formation of LTP by weaker tetanus (30 pulses at 60 Hz). When AP3 was injected after tetanus, it did not significantly affect the established LTP. These results suggest that metabotropic glutamate receptors play a role in facilitation of the formation of LTP in the dentate gyrus in vivo.