Inhibition of the phosphodiesterase 4 (PDE4) enzyme reverses memory deficits produced by infusion of the MEK inhibitor U0126 into the CA1 subregion of the rat hippocampus.
Cyclic AMP-specific phosphodiesterase 4 (PDE4), which is an integral component of NMDA receptor-mediated cAMP signaling, is involved in the mediation of memory processes. Given that NMDA receptors also mediate MEK/mitogen-activated protein kinase (MAPK, ERK) signaling, which is involved in synaptic plasticity, and that some PDE4 subtypes are phosphorylated and regulated by ERK, it was of interest to determine if PDE4 is involved in MEK/ERK signaling-mediated memory. It was found that rolipram, a PDE4-selective inhibitor, reversed the amnesic effect in the radial-arm maze test of the MEK inhibitor U0126 administered into the CA1 subregion of the rat hippocampus. Consistent with this, rolipram, either by peripheral administration or direct intra-CA1 infusion, enhanced the retrieval of long-term memory impaired by intra-CA1 infusion of U0126 using the step-through inhibitory avoidance test. The same dose of rolipram did not affect U0126-induced reduction of phospho-ERK1/2 levels in the CA1 subregion. However, in primary cultures of rat cerebral cortical neurons, pretreatment with U0126 increased PDE4 activity; this was correlated with the U0126-induced reduction of phospho-ERK1/2 levels. These results suggest that MEK/ERK signaling plays an inhibitory role in regulating PDE4 activity in the brain; this may be a novel mechanism by which MEK/ERK signaling mediates memory. PDE4 is likely to be an important link between the cAMP/PKA and MEK/ERK signaling pathways in the mediation of memory.
Zhang
Han-Ting
HT
Department of Pharmacology, The University of Tennessee Health Science Center, Memphis, TN 38163, USA. hzhang@utmem.edu
Zhao
Yu
Y
Huang
Ying
Y
Dorairaj
Nandakumar R
NR
Chandler
L Judson
LJ
O'Donnell
James M
JM
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors*; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D015153:Blotting, Western; D002070:Butadienes / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006624:Hippocampus; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D008569:Memory Disorders / Q000139:chemically induced* / Q000188:drug therapy*; D008845:Microinjections; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors*; D009474:Neurons / Q000187:drug effects / Q000201:enzymology; D009570:Nitriles / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D010726:Phosphodiesterase Inhibitors / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020889:Rolipram / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects
D002070:Butadienes; D004791:Enzyme Inhibitors; D009570:Nitriles; D010726:Phosphodiesterase Inhibitors; C113580:U 0126; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D020889:Rolipram