GAMMA-HYDROXYBUTYRIC ACID INCREASES INTRACELLULAR CA2-RESPONSIVE ELEMENT AND ACTIVATOR PROTEIN-1 DNA-BINDING ACTIVITIES THROUGH GABA(B), RECEPTOR IN CULTURED CEREBELLAR GRANULE CELLS( CONCENTRATION AND NUCLEARCYCLIC AMP)

In primary cultures of mouse cerebellar granule cells, a brief stimula tion by gamma-hydroxybutyric acid (GHB, 0.1-3 mM) significantly increa sed the intracellular Ca2+ concentration ([Ca2+]i) in a concentration- dependent manner, In addition, gel mobility assay showed that exposure of the cells to GHB also increased nuclear DNA-binding activity speci fic for the cyclic AMP-responsive element (CRE) and activator protein 1 (AP-1) transcriptional element in a concentration-dependent manner. The concentration range of GHB that increased the DNA-binding activity was essentially the same as the concentration range that elicited the increase in [Ca2(+)]i. The GHB-induced increases in [Ca2+]i and nucle ar DNA-binding activity were antagonized by specific GABA(B) antagonis ts such as p-[3-aminopropyl]-p-diethoxymethylphosphinic acid (CGP 35 3 48) and 3-N-[1-(S)-(3, orobenzyl)ethanol-2-(S)-hydroxy-P-benzylphosphi nic acid (CGP 55 845). In addition, the GHB-induced increase in [Ca2+] i was abolished by pretreatment of the cells with islet-activating pro tein. Furthermore, treatment of the cells with 2-bis(2'-aminophenoxy)e thane-N,N,N',N'-tetraacetic acid tetraacetoxymethyl ester (BAPTA-AM) a nd thapsigargin blocked the GHB-induced increase in nuclear DNA-bindin g activity. GHB inhibited [H-3]baclofen binding to cultured cerebellar granule cells and mouse cerebellar membranes. These results suggest t hat stimulation of GABA(B) receptors by GHB activates intracellular Ca 2+ stores and that the increased [Ca2+]i resulting from release of sto red Ca2+ plays an important role in increasing the CRE- and AP-1 DNA-b inding activities in cultured cerebellar granule cells.