Transcriptional regulation of POMC gene by secretagogues

435 Five-barrelled glass micropipettes were used for extracellular unitary recording in rats anesthetized with urethane (1.25 g/ kg, i.p.). The following solutions were applied by microiontophoresis: N M D A (10 nM in 200 mM NaCI, pH 8), quisqualate (1.5 mM in 400 mM NaC1, pH 8), kainate (1 mM in 400 mM NaCI, pH 8). DTG, JO-1781 and (+)pentazocine were injected in a tail vein. Whereas DTG selectively reduced NMDA-induced neuronal activation, ( + )pentazocine selectively potentiated the N M D A response and JO-1784 had no effect on the response to N M D A of CAI pyramidal neurons. Finally, haloperidol reduced both the inhibitory effect of DTG and the potentiating effect of( + )pentazocine. These results clearly show the different response of CA1 and CA3 pyramidal neurons to a ligands. Hence, they bring further support to the notion that several subtypes of a receptors exist in the mammalian central nervous system.

Transcriptional regulation of POMC gene by secretagogues

Mirela O. Ffigfir/tsan Department o]" Biochemistry and Molecular Biology, George Washington University, Washington, DC 20037, USA Key words'." Interleukin-l; c-Jun; c-Fos; Pituitary cells Interleukin 1 (IL-1), corticotropin releasing factor (CRF), phorbol ester and forskolin cause a time dependent increase in proopiomelanocortin gene (POMC) m R N A levels, adrenocorticotropin releasing factor (ACTH), and/#endorphin synthesis in normal pituitary cells and in ART-20 cells, a mouse anterior pituitary cell line. The role of immediate early genes c-fos and cjun on the ability of secretagogues to regulate POMC gene was determined. We found that CRF, TPA and forskolin induce cfos m R N A expression in a time and dose dependent manner. The levels of c-fos mRNA rise rapidly (within minutes) following the addition of forskolin, C R F and TPA to the cells. The effect was maximum after 15 30 min and returned to normal levels after 1 h. Also we found that IL-I induced c-fos and c-jun m R N A in a time and dose dependent manner. The treatment of the cells with antisense oligonucleotides to c-los abolished the induction of POMC m R N A by forskolin, C R F and TPA. Adding antisense oligonucleotides to c-fos and c-jun to pituitary cells, we abolished the ability of IL-I to induce POMC gene expression. These findings show that the transient induction of early immediate genes c-jun and/or c-los expression is a critical step in secretagogue-induced POMC m R N A expression in pituitary cells.

Gi/o proteins are involved in the potentiation of N-methyl-o-aspartate (NMDA) effects by sigma agonists and neuropeptide Y F.P. Monnet a'b, G. D e b o n n e P and C. de Montigny ~ UNeurobiological Psychiatry Unit, Department o/Psychiatry, McGill University, Montreal, Canada and Servtce de Psyctuatrw, Hopttal de Bwetre, Le Kremhn-Bwetre, France Key words." NMDA; G :o protein; Pertussis toxin; Sigma receptors; Haloperidol; Neuropeptide Y Previous data from our laboratory have shown that several sigma (a) ligands and NPY selectively modulate the N M D A induced activation of hippocampal pyramidal neurons via different subtypes of a receptors (Monnet et al., 1992a,b). The present experiments were carried out to determine if these receptors are coupled to Gi/o protein coupled mechanisms. Therefore, the in vivo and the in vitro effects of the high affinity er ligands 1,3-di(2-tolyl)guanidine (DTG), ( + ) N cyclopropylmethyl-N-methyl-1,4-diphenyl- 1-ethyl-but-3-en- l-ylamine hydrochloride (JO-1784), ( +)pentazocine, (+)3-[3hydroxyphenyl]-N-(l-propyl)piperidine hydrochloride ((+)3-PPP) and haloperidol, as well as that of NPY were assessed