title: Repeated administration of dexamethasone increases phosphoinositide-specific phospholipase C activity and mRNA and protein expression of the phospholipase C beta 1 isozyme in rat brain.
abstract: Altered hypothalamic-pituitary-adrenal (HPA) function has been shown to be associated with changes in mood and behavior. The enzyme phosphoinositide-specific phospholipase C (PI-PLC), an important component of the PI signal transduction system, plays a major role in mediating various physiological functions. In the present study, we investigated the effects of a single dose and of repeated administration (0.5 or 1.0 mg/kg for 10 days) of dexamethasone (DEX), a synthetic glucocorticoid, on PI-PLC activity and on expression of PLC isozymes (beta1, delta1, and gamma1) in rat brain. Repeated administration of DEX (1.0 mg/kg) caused a significant increase in PI-PLC activity and in protein expression of the PLC beta1 isozyme in both membrane and cytosol fractions of cortex and hippocampus; however, the repeated administration of a smaller dose of DEX (0.5 mg/kg) caused these changes only in hippocampus but not in cortex. The increase in PLC beta1 protein was associated with an increase in its mRNA level, as measured by competitive RT-PCR. A single administration of DEX (0.5 or 1.0 mg/kg) to rats had no significant effects on PI-PLC activity or on the protein expression of PLC isozymes. These results suggest that DEX up-regulates PI-PLC in rat brain, which presumably is due to a selective increase in expression of the PLC beta1 isozyme, and that these changes in PI-PLC may be related to HPA axis-mediated changes in mood and behavior.
authors.affiliation: Psychiatric Institute, Department of Psychiatry, College of Medicine, University of Illinois at Chicago, 60612, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Dwivedi
authors.forename: G N
authors.initials: GN
authors.lastname: Pandey
mesh_terms: D000339:Affect / Q000187:drug effects; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001921:Brain / Q000187:drug effects / Q000201:enzymology*; D003907:Dexamethasone / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D019204:GTP-Binding Proteins / Q000032:analysis; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology*; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000201:enzymology; D007527:Isoenzymes / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D008297:Male; D010716:Phosphatidylinositols / Q000378:metabolism; D054801:Phosphoinositide Phospholipase C; D054799:Phospholipase C beta; D054803:Phospholipase C delta; D010727:Phosphoric Diester Hydrolases / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D010913:Pituitary-Adrenal System / Q000187:drug effects / Q000201:enzymology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D010738:Type C Phospholipases / Q000032:analysis / Q000235:genetics* / Q000378:metabolism
chemical_list: D005938:Glucocorticoids; D007527:Isoenzymes; D010716:Phosphatidylinositols; D012333:RNA, Messenger; D003907:Dexamethasone; D010727:Phosphoric Diester Hydrolases; D010738:Type C Phospholipases; D054801:Phosphoinositide Phospholipase C; D054799:Phospholipase C beta; D054803:Phospholipase C delta; C518035:Plcb1 protein, rat; D019204:GTP-Binding Proteins; D043802:GTP-Binding Protein alpha Subunits, Gq-G11