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.
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.
Itoi
K
K
Third Department of Medicine, Hirosaki University School of Medicine, Japan.
Horiba
N
N
Tozawa
F
F
Sakai
Y
Y
Sakai
K
K
Abe
K
K
Demura
H
H
Suda
T
T
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000008:administration & dosage / Q000494:pharmacology; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D001483:Base Sequence; D003346:Corticotropin-Releasing Hormone / Q000235:genetics*; D000242:Cyclic AMP / Q000494:pharmacology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D016762:Genes, fos / Q000235:genetics; D016758:Genes, jun / Q000235:genetics; D007003:Hypoglycemia / Q000139:chemically induced / Q000378:metabolism; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D007328:Insulin; D008297:Male; D008845:Microinjections; D008969:Molecular Sequence Data; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism; D011333:Pro-Opiomelanocortin / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D007328:Insulin; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D015124:8-Bromo Cyclic Adenosine Monophosphate; D011333:Pro-Opiomelanocortin; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D013755:Tetradecanoylphorbol Acetate