title: Developmental switch from LTD to LTP in low frequency-induced plasticity.
abstract: The stimulation of the Schaffer collateral/commissural fibers at low frequency (1 Hz) for 3-5 min can trigger a slow-onset form of low-frequency stimulation (LFS)-long-term potentiation (LTP) (LFS-LTP) in the CA1 area of the adult rat hippocampus. Here we have examined the developmental profile of this plasticity. In 9-15 day-old rats, the application of 1 Hz for 5 min induced long-term depression (LFS-LTD). In 17-21 day-old rats, 1 Hz stimulation had no effect when applied for 5 min but mediated LTD when stimulus duration was increased to 15 min. Over 25 day-old, 1 Hz stimulation mediated LFS-LTP. LFS-LTD was dependent on both N-methyl-D-aspartate (NMDA) and mGlu5 receptor activation. Antagonists of mGlu1alpha and cannabinoid type 1 receptor were ineffective to block LTD induction. LFS-LTD was not associated with a change in paired-pulse facilitation ratio, suggesting a postsynaptic locus of expression of this plasticity. Next, we examined whether LFS-LTD was related to 'chemical' LTDs obtained by the direct stimulation of mGlu5 and NMDA receptors. The saturation of LFS-LTD completely occluded NMDA- and (RS)-2-Chloro-5-hydroxyphenylglycine (CHPG)-induced LTD. CHPG-LTD and NMDA-LTD occluded each other. In addition, we observed that NMDA-LTD was dependent on mGlu5 receptor activation in 9-12 day old rats while it was not in animals older than 15 day-old. Therefore we postulate that during LFS application, NMDA and mGlu5 receptor could interact to trigger LTD. Low-frequency-mediated synaptic plasticity is subject to a developmental switch from NMDA- and mGlu5 receptor-dependent LTD to mGlu5 receptor-dependent LTP with a transient period (17-21 day-old) during which LFS is ineffective.
authors.affiliation: Laboratory Oxidative Stress and Neuroprotection, University Montpellier II, Montpellier, Cedex, France.
authors.forename: Fabien
authors.initials: F
authors.lastname: Lanté
authors.forename: Mélanie
authors.initials: M
authors.lastname: Cavalier
authors.forename: Catherine
authors.initials: C
authors.lastname: Cohen-Solal
authors.forename: Janique
authors.initials: J
authors.lastname: Guiramand
authors.forename: Michel
authors.initials: M
authors.lastname: Vignes
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D048588:Benzoxazines; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004307:Dose-Response Relationship, Radiation; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D006624:Hippocampus / Q000254:growth & development / Q000502:physiology* / Q000528:radiation effects; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D036881:Long-Term Synaptic Depression / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D008297:Male; D009025:Morpholines / Q000494:pharmacology; D016202:N-Methylaspartate / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D010648:Phenylacetates / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D051381:Rats
chemical_list: C107349:2-chloro-5-hydroxyphenylglycine; D048588:Benzoxazines; D002121:Calcium Channel Blockers; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D009025:Morpholines; D009281:Naphthalenes; D010648:Phenylacetates; D010880:Piperidines; D011720:Pyrazoles; C103505:AM 251; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; D016202:N-Methylaspartate; D005998:Glycine