Gαi and Gβγ subunits have opposite effects on dexmedetomidine-induced sedation / 中国药理学与毒理学杂志

ABSTRACT

OBJECTIVE To explore the mechanism of Gαiand Gβγsubunits on dexmedetomidine (DMED)-induced sedation.METHODS Kunming mice were randomly placed into three groups(DMED group, DMED+dbcAMP/rolipram/gallein/M119 group, dbcAMP/rolipram/gallein/M119 group) to explore the regulation of dbcAMP/rolipram/gallein/M119 on DMED-induced sedation by establishing loss of righting reflex (LORR) model. DbcAMP/rolipram was intracerebroventricular injected and gallein/M119 was intraperitoneal injected 15 min before DMED intravenous injection. In CHO-α2A-AR cells, after administration of DMED/gallein/M119, the regulation on the cAMP accumulation stimulated by Forskolin (FSK) was detected, so was the intracellular calcium ion concentration ([Ca2+]i. The levels of pERK/pCREB were detected by Western Blot to explore the key signal molecules involved in DMED-induced sedation. RESULTS The ED50of DMED-induced LORR (200.0 nmol·kg-1) was increased to 375.0 or 433.3 nmol·kg-1by pre-treatment with cAMP analog dbcAMP(50 nmol/5μl per mouse)or phosphodies-terase 4 inhibitor rolipram(100 nmol/5μl per mouse).In addition,the ED50of DMED-induced LORR was decreased to 113.6 or 136.5 nmol·kg-1when pre-treated with Gβγsubunits inhibitor M119(100 mg·kg-1) or gallein(100 mg·kg-1)respectively.Administration of dbcAMP,rolipram,gallein or M119 alone had little effect on LORR of mice.Gallein(10 μmol·L-1)significantly inhibited forskolin-stimulated cAMP accumu-lation in CHO-α2A-AR cells.Compared with Gβγsubunits inhibitors or DMED alone,[Ca2+]iand pERK1/2 significantly increased after co-administration of Gβγsubunits inhibitors with DMED.DbcAMP(5 μmol·L-1) or rolipram (5 μmol·L- 1) alone had little effect on ERK1/2 phosphorylation, but decreased DMED-induced ERK1/2 phosphorylation after co-administration with DMED. Gβγsubunit inhibitors treatment increased DMED-induced phosphorylation of CREB, whereas dbcAMP or rolipram had little effect on pCREB induced by DMED.CONCLUSION Gβγsubunits might inhibit DMED-induced sedation through cAMP and pERK1/2 pathway,which was opposite to Gαisubuint.