Subtype-specific involvement of metabotropic glutamate receptors in two forms of long-term potentiation in the dentate gyrus of freely moving rats.
In this study, the role of metabotropic glutamate receptors in N-methyl-D-aspartate receptor-dependent and voltage-gated calcium channel-dependent long-term potentiation in the dentate gyrus of freely moving rats was investigated. Antagonists for group 1 metabotropic glutamate receptors ((S)-4-carboxyphenylglycine), group 1/2 metabotropic glutamate receptors ((RS)-alpha-methyl-4-carboxyphenylglycine) and group 2 metabotropic glutamate receptors ((RS)-alpha-methylserine O-phosphate monophenylester) were used. The N-methyl-D-aspartate receptor antagonist, D(-)-2-amino-5-phosphonopentanoic acid, and the L-type voltage-gated calcium channel antagonist, methoxyverapamil were used to investigate the N-methyl-D-aspartate receptor and voltage-gated calcium channel contribution to the long-term potentiation recorded. Field excitatory postsynaptic potential slope and population spike amplitude were measured. Drugs were applied, prior to tetanus, via a cannula implanted into the lateral cerebral ventricle. 200 Hz tetanization produces a long-term potentiation which is inhibited by application of D(-)-2-amino-5-phosphonopentanoic acid and (RS)-alpha-methyl-4-carboxyphenylglycine. In this study, a dose-dependent inhibition of 200 Hz long-term potentiation expression was obtained with (S)-4-carboxyphenylglycine. Long-term potentiation induced by 400 Hz tetanization was not inhibited by D(-)-2-amino-5-phosphonopentanoic acid, although the amplitude of short-term potentiation was reduced. (RS)-alpha-methyl-4-carboxyphenylglycine and (S)-4-carboxyphenylglycine, both in the presence and absence of D(-)-2-amino-5-phosphonopentanoic acid, inhibited the development of 400 Hz long-term potentiation. (RS)-alpha-methylserine O-phosphate monophenylester had no significant effect on long-term potentiation induced by either 200 or 400 Hz tetanization. Application of methoxyverapamil significantly inhibited 400 Hz long-term potentiation, but had no effect on 200 Hz long-term potentiation. These data suggest that 400 Hz long-term potentiation, induced in the presence of D(-)-2-amino-5-phosphonopentanoic acid, requires activation of L-type calcium channels. Furthermore, these results strongly support a critical role for group 1 metabotropic glutamate receptors in both N-methyl-D-aspartate receptor- and voltage-gated calcium channel-dependent long-term potentiation.
Federal Institute for Neurobiology, Department of Neurophysiology, Magdeburg, Germany.
D
D
Manahan-Vaughan
K H
KH
Braunewell
K G
KG
Reymann
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D001565:Benzoates / Q000494:pharmacology; D018891:Dentate Gyrus / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology*; D005711:Gallopamil / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D018094:Receptors, Metabotropic Glutamate / Q000187:drug effects / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
D001565:Benzoates; D018691:Excitatory Amino Acid Antagonists; D018094:Receptors, Metabotropic Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D005711:Gallopamil; C079693:4-carboxyphenylglycine; D015763:2-Amino-5-phosphonovalerate; D005998:Glycine