title: Signaling mechanisms underlying group I mGluR-induced persistent AHP suppression in CA3 hippocampal neurons.
abstract: Activation of group I metabotropic glutamate receptors (mGluRs) leads to a concerted modulation of spike afterpotentials in guinea pig hippocampal neurons including a suppression of both medium and slow afterhyperpolarizations (AHPs). Suppression of AHPs may be long-lasting, in that it persists after washout of the agonist. Here, we show that persistent AHP suppression differs from short-term, transient suppression in that distinct and additional signaling processes are required to render the suppression persistent. Persistent AHP suppression followed DHPG application for 30 min, but not DHPG application for 5 min. Persistent AHP suppression was temperature dependent, occurring at 30-31 degrees C, but not at 25-26 degrees C. Preincubation of slices in inhibitors of protein synthesis (cycloheximide or anisomycin) prevented the persistent suppression of AHPs by DHPG. Similarly, preincubation of slices in an inhibitor of p38 MAP kinase (SB 203580) prevented persistent AHP suppression. In contrast, a blocker of p42/44 MAP kinase activation (PD 98059) had no effect on persistent AHP suppression. Additionally, we show that the mGluR5 antagonist MPEP, but not the mGluR1 antagonist LY 367385, prevented DHPG-induced persistent AHP suppression. Thus persistent AHP suppression by DHPG in hippocampal neurons requires activation of mGluR5. In addition, activation of p38 MAP kinase signaling and protein synthesis are required to impart persistence to the DHPG-activated AHP suppression.
authors.affiliation: Department of Physiology and Pharmacology, SUNY Downstate Medical Center, 450 Clarkson Ave., Brooklyn, NY 11203, USA. syoung@downstate.edu
authors.forename: Steven R
authors.initials: SR
authors.lastname: Young
authors.forename: Riccardo
authors.initials: R
authors.lastname: Bianchi
authors.forename: Robert K S
authors.initials: RK
authors.lastname: Wong
mesh_terms: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D003513:Cycloheximide / Q000494:pharmacology; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D006168:Guinea Pigs; D006624:Hippocampus / Q000166:cytology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D008734:Methoxyhydroxyphenylglycol / Q000031:analogs & derivatives / Q000494:pharmacology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D018091:Receptors, AMPA / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D013696:Temperature
chemical_list: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D003513:Cycloheximide; D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D008734:Methoxyhydroxyphenylglycol; D011500:Protein Synthesis Inhibitors; D018091:Receptors, AMPA; C010117:3,4-dihydroxyphenylglycol