CCG-203920 potentiated the NOP response in rat primary striatal neurons
To investigate the occurrence of a RGS4-NOP receptor interaction in native tissues, the impact of pharmacological inhibition of RGS4 on NOP responses was investigated in DARPP32+ neurons in primary cultures of the E14 rat striatum (Fig. 2). cAMP accumulation was measured in DARPP32+ neurons stimulated with the D1 receptor agonist SKF-38393 (100 µM) combined with increasing concentrations of N/OFQ, in the presence or the absence of the RGS4 inhibitor CCG-203920 (100 nM). SKF-38393 caused an 83% increase of cAMP levels that was not significantly affected by CCG-203920 (Fig. 2A). N/OFQ inhibited the stimulation induced by SKF-38393 in a concentration-dependent manner with an pIC50 of 10.81 (11.36-10.26) and a 70% maximal inhibition of cAMP levels (Fig. 2B). CCG-203920 caused a leftward shift of N/OFQ pIC50 to 11.55 (12.43-10.67), without changing N/OFQ efficacy (Fig. 2B).