(A) Inhibition of Ca2+ -independent and –dependent isoforms of PKC (GF 109203X) enhanced basal levels of 5-HT2A receptor mRNA. *p<0.05, significant effect of GP 1a treatment, GF 109203X pretreatment, and GP 1a/GF 109203X treatment compared to vehicle-treated controls. (B) Inhibition of Ca2+ -dependent isoforms of PKC (Go 6967) enhanced basal levels of 5-HT2A receptor mRNA. **p<0.01, significant effect of GP 1a treatment, Go 6967 pretreatment, and GP 1a/Go 6967 treatment compared to vehicle-treated controls. (C) Activation of Ca2+ -independent and -dependent isoforms of PKC (PDBu) prevented GP 1a-induced increases in 5-HT2A receptor mRNA. *p<0.05, significant effect of GP 1a treatment compared to vehicle-treated controls. #p<0.05, significant effect of PDBu pretreatment on GP 1a-induced increases in 5-HT2A receptor mRNA. (D) Activation of Ca2+ -dependent isoforms of PKC did not prevent GP 1a-induced increases in 5-HT2A receptor mRNA. **p<0.01, significant effect of GP 1a treatment compared to vehicle-treated controls. The data represent mean ± SEM (n=3).