Rophysiometer, where pretreatment of CHORXFP3 cells with PTX strongly inhibited the extracellular acidification rate, suggesting that the signaling pathways activated by RXFP3 were downstream of Gai/o (van der Westhuizen et al., 2005). As for RXFP1 and RXFP2, PTX-insensitive G proteins were used to determine the particular G proteins involved (van der Westhuizen, 2008). PTX pretreatment completed