title: Molecular mechanisms of group I metabotropic glutamate receptor mediated LTP and LTD in basolateral amygdala in vitro.
abstract: The roles of group I metabotropic glutamate receptors, metabotropic glutamate receptor 1 (mGluR1) and mGluR5, in regulating synaptic plasticity and metaplasticity in the basolateral amygdala (BLA) remain unclear. The present study examined mGluR1- and mGluR5-mediated synaptic plasticity in the BLA and their respective signaling mechanisms. Bath application of the group I mGluR agonist, 3,5-dihydroxyphenylglycine (DHPG) (20 μM), directly suppressed basal fEPSPs (84.5 ± 6.3% of the baseline). The suppressive effect persisted for at least 30 min after washout; it was abolished by the mGluR1 antagonist 7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxylate ethyl ester (CPCCOEt) but was unaffected by the mGluR5 antagonist 2-methyl-6- (phenylethynyl)-pyridine (MPEP). Interestingly, application of DHPG (at both 2 and 20 μM), regardless of the presence of CPCCOEt, could transform single theta burst stimulation (TBS)-induced short-term synaptic potentiation into a long-term potentiation (LTP). Such a facilitating effect could be blocked by the mGluR5 antagonist MPEP. Blockade of phospholipase C (PLC), the downstream enzyme of group I mGluR, with U73122, prevented both mGluR1- and mGluR5-mediated effects on synaptic plasticity. Nevertheless, blockade of protein kinase C (PKC), the downstream enzyme of PLC, with chelerythrine (5 μM) only prevented the transforming effect of DHPG on TBS-induced LTP and did not affect DHPG-induced long-term depression (LTD). These results suggest that mGluR1 activation induced LTD via a PLC-dependent and PKC-independent mechanism, while the priming action of mGluR5 receptor on the BLA LTP is both PLC and PKC dependent. The BLA metaplasticity mediated by mGluR1 and mGluR5 may provide signal switching mechanisms mediating learning and memory with emotional significance.
authors.affiliation: Department of Physiology, Fujian Medical University, Fuzhou, People's Republic of China.
authors.forename: A
authors.initials: A
authors.lastname: Chen
authors.affiliation: Department of Physiology, Fujian Medical University, Fuzhou, People's Republic of China.
authors.forename: W W
authors.initials: WW
authors.lastname: Hu
authors.affiliation: Department of Psychiatry, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD, 20814-4799, USA.
authors.forename: X L
authors.initials: XL
authors.lastname: Jiang
authors.affiliation: Department of Pediatrics, University of Minnesota, Minneapolis, MN, 55414, USA.
authors.forename: M
authors.initials: M
authors.lastname: Potegal
authors.affiliation: Department of Psychiatry, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD, 20814-4799, USA. he.li@usuhs.edu.
authors.forename: H
authors.initials: H
authors.lastname: Li
mesh_terms: D000818:Animals; D066272:Basolateral Nuclear Complex / Q000187:drug effects*; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects*; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D017774:Long-Term Potentiation / Q000187:drug effects*; D036881:Long-Term Synaptic Depression / Q000187:drug effects*; D008297:Male; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D064529:Receptor, Metabotropic Glutamate 5 / Q000378:metabolism; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists; D012118:Resorcinols / Q000494:pharmacology
chemical_list: D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D011725:Pyridines; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; D012118:Resorcinols; C079215:3,5-dihydroxyphenylglycine; C121465:6-methyl-2-(phenylethynyl)pyridine; D005998:Glycine
keywords: DHPG; LTD; LTP; MPEP; PKC; Synaptic plasticity