Major role of 3',5'-cyclic adenosine monophosphate-dependent protein kinase A pathway in corticotropin-releasing factor gene expression in the rat hypothalamus in vivo

• Published in: Endocrinology (Philadelphia) 1996-06, Vol.137 (6), p.2389-2396
• Main Authors: Itoi, K, Horiba, N, Tozawa, F, Sakai, Y, Sakai, K, Abe, K, Demura, H, Suda, T
• Format: Article
• Language: English
• Subjects: 8-Bromo Cyclic Adenosine Monophosphate - administration & dosage; 8-Bromo Cyclic Adenosine Monophosphate - pharmacology; Acetic acid; Activator protein 1; Adenosine kinase; Adenosine monophosphate; Adrenocorticotropic hormone; Adrenocorticotropic Hormone - blood; AMP; Animals; Antisense oligonucleotides; Antisense RNA; Base Sequence; c-Fos protein; c-Jun protein; Corticotropin-releasing hormone; Corticotropin-Releasing Hormone - genetics; Cyclic AMP - pharmacology; Cyclic AMP response element-binding protein; Cyclic AMP-Dependent Protein Kinases - metabolism; Diglycerides; Gene expression; Gene Expression - drug effects; Genes, fos - genetics; Genes, jun - genetics; Hypoglycemia; Hypoglycemia - chemically induced; Hypoglycemia - metabolism; Hypothalamus; Hypothalamus - drug effects; Hypothalamus - metabolism; Injection; Insulin; Kinases; Male; Microinjection; Microinjections; Molecular Sequence Data; Neurons; Oligonucleotides, Antisense - pharmacology; Paraventricular Hypothalamic Nucleus - drug effects; Paraventricular Hypothalamic Nucleus - metabolism; Paraventricular nucleus; Physiological effects; Physiology; Pituitary (anterior); Pro-Opiomelanocortin - genetics; Proopiomelanocortin; Protein kinase A; Protein kinase C; Proteins; Rats; Rats, Wistar; RNA, Messenger - metabolism; Tetradecanoylphorbol Acetate - pharmacology; Transcription activation; Transcription factors
• ISSN: 0013-7227; 1945-7170
• DOI: 10.1210/en.137.6.2389

To assess whether the cAMP-dependent protein kinase-A and/or the diacylglycerol-dependent protein kinase C (PKC) pathways play important roles in the activation of CRF neurons in vivo under physiological conditions, we tested the effect of microinjection of 8-bromo-cAMP (8-Br-cAMP) or 12-O-tetradecanoyl phorbol 13-acetate (TPA) into both paraventricular nuclei (PVN) of the hypothalamus in conscious rats. Both 8-Br-cAMP and TPA increased plasma ACTH concentrations and the POMC messenger RNA (mRNA) concentrations in the anterior pituitary. While injection of 8-Br-cAMP also increased CRF mRNA concentrations in hypothalamic tissue containing the PVN, TPA injection had no effect on CRF mRNA concentrations there. During insulin-induced hypoglycemia, which stimulates CRF gene expression and release, c-fos and c-jun mRNA increases in the hypothalamic tissue preceded the increase in the CRF mRNA level after insulin-induced hypoglycemia. Antisense oligodeoxyribonucleotides (oligos) directed against c-fos, c-jun, or the cAMP response element binding protein (CREB) mRNA were injected into both PVN before insulin-induced hypoglycemia to assess whether activator protein-1 or CREB mediates transcriptional activation of CRF during hypoglycemia. Only antisense oligo against CREB mRNA reduced the CRF mRNA level after insulin-induced hypoglycemia. These results suggest that protein kinase A may transduce intracellular signals in CRF neurons under physiological conditions and raises the possibility that CREB may be involved in stress-induced CRF gene expression.