Figure 4.

GP 1a, a selective CB2 receptor agonist, upregulates 5-HT_2A receptors via ERK1/2 signaling in CLU213 and A1A1v cells. (A) PD198306, a selective ERK1/2 inhibitor, prevented the effect of GP 1a on 5-HT_2A receptor mRNA levels in CLU213 and A1A1v cells. ^**p<0.01, significant effect of GP 1a treatment on 5-HT_2A receptor mRNA levels compared to vehicle treated CLU213 or A1A1v cells. ^##p<0.01, significant effect of PD 198306 pretreatment on the GP 1a-induced upregulation of 5-HT_2A receptor mRNA in CLU213 cells. (B) PD198306 prevented GP 1a-induced ERK1/2 activation. ^**p<0.01, significant effect of GP 1a treatment on nuclear pERK levels compared to vehicle control. ^##p<0.01, significant effect of GP 1a treatment on nuclear pERK levels compared to the effect of GP 1a treatment in PD198306 pretreated cells. ^&p<0.05, significant effect of PD198306 pretreatment compared to vehicle controls (C) PD198306 prevented the GP 1a-induced increases in 5-HT_2A receptor protein levels in CLU213 cells. ^*p<0.05, significant effect of GP 1a treatment on 5-HT_2A receptor protein levels compared to vehicle treated cells. ^#p<0.05, significant effect of GP 1a treatment on 5-HT_2A receptor protein levels compared to the effect of GP 1a treatment in PD198306 pretreated cells. The data represent mean ± SEM (n=3).