Functional α 2C-adrenoceptors in human neuroblastoma SH-SY5Y cells

Abstract

The α 2-adrenoceptor mediating inhibition of forskolin-stimulated cyclic AMP accumulation in human neuroblastoma SH-SY5Y cells was further characterized. The α 2-adrenoceptor agonists, UK 14,304 (5-bromo-6-(2-imidazolin-2-ylamino)quinoxaline), oxymetazoline, guanfacine, (−)-noradrenaline and clonidine concentration-dependently decreased cyclic AMP accumulation in this cell line ( E max ca. 50% inhibition). Agonist pEC 50 values ranged between 6.7 and 7.8. Clonidine was a partial agonist. The effects of UK 14,304 were blocked after a pertussis toxin treatment. The concentration–response curves of UK 14,304 were shifted to the right in a parallel manner by the following antagonists (mean p K B values): yohimbine (8.17), idazoxan (7.63), prazosin (6.66), 2-[2-(4-(2-methoxyphenyl)piperazin-1-yl)ethyl]-4,4-dimethyl-1,3-(2H,4H) isoquinolindione (ARC 239; 7.12) and 2-(2,6-dimethoxyphenoxyethyl)aminomethyl-1,4-benzodioxane (WB-4101; 8.12). The relatively high p K B values of prazosin and ARC 239 point to a non-α 2A-adrenoceptor-mediated effect. The relatively high p K B value of WB-4101 further characterizes the α 2-adrenoceptor in SH-SY5Y cells as being of the α 2C subtype. The analysis of the expression of α 2-adrenoceptor subtypes by reverse transcriptase-polymerase chain reaction (RT-PCR) revealed the exclusive presence of α 2C-adrenoceptor mRNA in SH-SY5Y cells. We propose that inhibition of forskolin-stimulated cAMP accumulation in SH-SY5Y cells be used as a functional model of human, native α 2C-adrenoceptors.