Inducible cAMP early repressor regulates corticosterone suppression after tricyclic antidepressant treatment.
The cAMP-response element binding protein (CREB) is involved in antidepressant action, but the role of related CRE-binding transcription factors in the behavioral and endocrine responses to antidepressants is unclear. Alternative transcription of the cAMP response element-modulator (CREM) gene yields activator and repressor isoforms, including the strong repressor inducible cAMP early repressor (ICER). ICER is highly expressed in hypothalamic tissues and upregulated after electroconvulsive seizure. Thus, ICER may be a novel mediator of antidepressant action at endocrine and/or behavioral levels. Here we establish that both subchronic and chronic desipramine (DMI) treatments upregulate hypothalamic ICER expression in wild-type mice. Behavioral responses to DMI in the forced swim and tail suspension tests are unchanged in mice lacking ICER. However, the ability of DMI to suppress an acute corticosterone response after swim stress is compromised in ICER-deficient mice, suggesting that increased hypothalamic ICER mRNA after DMI treatment may be required for suppression of corticosterone release. To investigate the mechanism underlying this response, we measured corticotropin releasing factor (CRF), an upstream modulator of corticosterone release. Using real-time quantitative PCR, we establish that hypothalamic CRF expression is significantly reduced after swim exposure in DMI-treated wild-type mice, however DMI is unable to blunt hypothalamic CRF expression in ICER-deficient mice. Furthermore, we demonstrate that ICER is enriched in CRF-expressing neurons in the paraventricular nucleus of the hypothalamus. These data indicate that ICER is required for DMI to reduce stress-induced corticosterone release through regulation of hypothalamic CRF expression, revealing a novel role for ICER in antidepressant regulation of the hypothalamic-pituitary adrenal axis.
Department of Pharmacology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Alana C
AC
Conti
Yuo-Chen
YC
Kuo
Rita J
RJ
Valentino
Julie A
JA
Blendy
D000818:Animals; D000929:Antidepressive Agents, Tricyclic / Q000494:pharmacology*; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D003345:Corticosterone / Q000037:antagonists & inhibitors / Q000378:metabolism*; D003346:Corticotropin-Releasing Hormone / Q000235:genetics / Q000378:metabolism; D051786:Cyclic AMP Response Element Modulator; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D003891:Desipramine / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D008817:Mice, Mutant Strains; D009474:Neurons / Q000378:metabolism; D010286:Paraventricular Hypothalamic Nucleus / Q000378:metabolism; D010913:Pituitary-Adrenal System / Q000187:drug effects / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013312:Stress, Physiological / Q000188:drug therapy / Q000378:metabolism
D000929:Antidepressive Agents, Tricyclic; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; D051786:Cyclic AMP Response Element Modulator; D003346:Corticotropin-Releasing Hormone; D003891:Desipramine; D003345:Corticosterone