(A,B,C,D) [3H]Ketanserin specific binding (2 nM) displacement curves by altanserin in postmortem frontal cortex of schizophrenic subjects (C,D) and controls (A,B) in the presence and in the absence of the non-hydrolyzable GTP analog Gpp(NH)p. The presence of Gpp(NH)p increases the fraction of high-affinity binding of altanserin displacing [3H]ketanserin binding in antipsychotic-free (AP-F) (C,E) and antipsychotic-treated (AP-T) (D,F) schizophrenics, but not in individually matched controls (A,B,E,F). ***p<0.001; n.s., not significant; Student’s t-test. See Supplementary Tables 1 and 2 for demographic information. See Table 2 for statistical analysis. All values represent means±SEM.