When are class I metabotropic glutamate receptors necessary for long-term potentiation?
The involvement of metabotropic glutamate receptors (mGluRs) in hippocampal long-term potentiation (LTP) is a matter of controversial debate. Using [Ca2+]i measurements by confocal laser scanning microscopy and field recordings of EPSPs (fEPSPs) in the hippocampal CA1-region, we found that the efficacy of the broad-spectrum mGluR-antagonist (S)-alpha-methyl-4-carboxyphenylglycine (MCPG) and of (S)-4-carboxy-phenylglycine (4-CPG), a selective antagonist at class I mGluRs, in LTP is contingent on the tetanization strength and the resulting [Ca2+]i response. As indicated by experiments in which we blocked voltage-dependent calcium channels (VDCCs) and intracellular Ca2+ stores (ICSs), the functional significance of class I mGluRs in LTP is confined to certain types of potentiation, which are induced by weak tetanization protocols and require the release of Ca2+ from ICSs for induction. During strong tetanic stimulation, this Ca2+ source is functionally bypassed by activating VDCCs.
Wilsch
V W
VW
Leibniz Institute for Neurobiology, Department of Neurophysiology, D-39008 Magdeburg, Germany.
Behnisch
T
T
Jäger
T
T
Reymann
K G
KG
Balschun
D
D
D000818:Animals; D001565:Benzoates / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D006624:Hippocampus / Q000502:physiology / Q000648:ultrastructure; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology*; D008297:Male; D018613:Microscopy, Confocal; D009119:Muscle Contraction / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors / Q000502:physiology*
D001565:Benzoates; D018691:Excitatory Amino Acid Antagonists; D018094:Receptors, Metabotropic Glutamate; C079694:alpha-methyl-4-carboxyphenylglycine; C079693:4-carboxyphenylglycine; D002118:Calcium; D005998:Glycine