A specific role for group I mGluRs in hippocampal LTP and hippocampus-dependent spatial learning.

Abstract

Metabotropic glutamate receptors (mGluRs) have been implicated in long-term potentiation and in learning and memory formation. In this study, we tested the effects of group I mGluR inhibition on synaptic plasticity and learning of rats at different levels of organization (1) in the hippocampal slice preparation; (2) in freely moving animals implanted with chronic hippocampal electrodes; and (3) in different spatial learning paradigms. To allow a direct comparison of the effects obtained the same doses were used in all paradigms. Bath-application of the selective group I mGluR antagonist (S)4-carboxyphenylglycine (4-CPG) impaired a decremental long-term potentiation (LTP) induced by a weak tetanization paradigm, but failed to affect a robust LTP generated by strong tetanization. In contrast, 4-CPG impaired a robust LTP in freely moving animals if applied 30 min before tetanization. The same dose of 4-CPG only impeded spatial learning mildly in the eight-arm radial maze and had no effect on a simple configuration of the Y-maze spatial alternation task. In the more difficult configuration of this task, however, 4-CPG caused complete amnesia. The lack of state-dependent 4-CPG actions and the absence of any 4-CPG effects in the open-field test classify the obtained retention deficit as a selective impairment of memory storage. Our results indicate a specific role of group I mGluRs in certain types of synaptic plasticity and of spatial learning.

• Authors: D Balschun, D Manahan-Vaughan, T Wagner, T Behnisch, K G Reymann, W Wetzel
• Journal: Learning & memory (Cold Spring Harbor, N.Y.) (Learn Mem) 1999 Mar-Apr Vol. 6 Issue 2 Pg. 138-52 ISSN: 1072-0502 [Print] United States
• PMID: 10327239 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Benzoates
• Excitatory Amino Acid Antagonists
• Receptors, Metabotropic Glutamate
• 4-carboxyphenylglycine
• Glycine

Topics

• Animals
• Benzoates (pharmacology)
• Electrophysiology
• Evoked Potentials, Somatosensory (drug effects, physiology)
• Excitatory Amino Acid Antagonists (pharmacology)
• Glycine (analogs & derivatives, pharmacology)
• Hippocampus (physiology)
• Long-Term Potentiation (physiology)
• Male
• Maze Learning (physiology)
• Neuronal Plasticity (physiology)
• Rats
• Rats, Wistar
• Receptors, Metabotropic Glutamate (physiology)