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Biol Psychiatry. 2008 Feb 15;63(4):353-9. Epub 2007 Sep 24.

Regionally specific regulation of ERK MAP kinase in a model of antidepressant-sensitive chronic depression.

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Interdepartmental Neuroscience Program, Department of Psychiatry, Yale University, New Haven, Connecticut 06508, USA.



Elevated phosphorylation of neurotrophin-regulated transcription factors, such as cyclic adenosine monophosphate (cAMP)-response element binding protein (CREB), in the hippocampus has been proposed as a common mediator of antidepressant (ADT) efficacy in otherwise naive rodents. The intracellular factors by which ADTs and glucocorticoids, causal factors in depression, regulate depression-like behavior remain unclear, but extracellular signal-regulated kinase 1/2 (ERK1/2), upstream of CREB, is a likely candidate.


We explored the long-term consequences of glucocorticoid exposure and subsequent ADT treatment in a novel model of chronic depression. Motivated behaviors, immobility during tail suspension, and ERK1/2, known to be required for behavioral response to ADTs, were quantified.


Chronic corticosterone (CORT) increased immobility, decreased responding in an operant conditioning task of motivation, and selectively reduced phosphorylated ERK1/2 (pERK1/2) in the dentate gyrus. Behavioral and biochemical measures were restored to baseline by amitriptyline (AMI) treatment. Corticosterone regulated pERK1/2 on a time course that paralleled increases in heat shock proteins associated with depression and decreased tyrosine kinase receptor B (trkB) phosphorylation. Chronic AMI also produced regionally dissociable effects on pERK1/2 in CA1/CA3, amygdala, and striatum, but not prefrontal cortex.


Antidepressant efficacy in a motivational task and behavioral despair assay are associated with altered limbic pERK1/2, including restored pERK1/2 in the dentate gyrus after stress-related insult.

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