Subjective Responses to Procaine
Within-group comparisons found that both the healthy comparison subjects (N=10) and the cocaine-addicted subjects (N=10) endorsed a significant “drug effect” of procaine compared to saline (mean=5.7, SD=0.5, z=–2.92, p=0.004, and mean=5.1, SD=1.0, z=–2.84, p=0.005, respectively), a significant “bad effect” of procaine (mean=5.4, SD=0.7, z=–2.86, p=0.004, and mean=3.0, SD=2.1, z=–2.55, p<0.02), and a significant “dislike” of procaine (mean=5.8, SD=0.4, z=–2.41, p<0.003, and mean=3.4, SD=2.8, z=–2.97, p<0.02). The cocaine-addicted subjects also reported a significant “good effect” after procaine infusion (mean=1.9, SD=2.2, z=–2.21, p<0.03). After procaine infusion, the healthy comparison subjects reported higher levels of “bad effect” compared to the cocaine-addicted subjects (z=–2.92, p<0.003, N=20). The cocaine-addicted subjects reported that the effect of procaine was only slightly similar to the effect of cocaine (mean=2.1 on a scale from 0, not similar, to 6, strongest level of similarity, SD=2.0).
Basal measures of SCL-90-R were very low in both groups before each study session, suggesting the absence of anticipatory anxiety. There were no significant within- or between-group differences after saline infusion. Compared to saline (Δprocaine response – Δsaline response), procaine administered to the comparison subjects (N=10) produced significant increases in scores for somatization (mean increase=1.33, SD=0.54, z=–2.80, p<0.005), obsessive-compulsive symptoms (mean increase=0.40, SD=0.35, z=–2.40, p<0.02), interpersonal sensitivity (mean increase=0.16, SD=0.16, z=–2.21, p<0.03), depression (mean increase=0.40, SD=0.41, z=–2.40, p<0.02), and anxiety (mean increase=1.73, SD=0.72, z=–2.80, p<0.005) and in the positive symptom total score (frequency of response) (mean increase=22.10, SD=9.53, z=–2.80, p<0.005), positive symptom distress index (severity of response) (mean increase=1.71, SD=0.14, z=–2.80, p<0.005), and global severity index (severity × frequency of response) (mean increase=0.55, SD=0.26, z=–2.80, p<0.005). After procaine infusion, compared to saline, the cocaine-addicted subjects (N=10) reported significant increases in somatization (mean increase=0.58, SD=0.56, z=–2.80, p<0.005), obsessive-compulsive symptoms (mean increase=0.40, SD=0.33, z=–2.67, p<0.02), depression (mean increase=0.42, SD=0.46, z=–2.67, p<0.008), anxiety (mean increase =1.07, SD=0.74, z=–2.67, p<0.008), and psychoticism (mean increase=0.33, SD=0.46, z=–2.12, p<0.04) and in the positive symptom total score (mean increase=18.90, SD=11.08, z=–2.67, p<0.008), positive symptom distress index (mean increase=0.74, SD=0.86, z=–2.80, p<0.005), and global severity index (mean increase=0.42, SD=0.35, z=–2.80, p<0.005). In between-group comparisons, the healthy subjects reported higher levels of somatization (z=–2.57, p<0.005, N=20) and a higher positive symptom distress index (z=–2.42, p<0.02, N=20) than the cocaine-addicted subjects after procaine exposure.
Change in rCBF and Subjective Response to Procaine
The healthy comparison subjects demonstrated positive relationships between aversive subjective response (responses to the third question [“bad effect”] and fifth question [“disliked the effect”] on the Drug Assessment Questionnaire) and the percent change in rCBF (rCBF in response to procaine – rCBF in response to saline) in the left (r=0.82, df=9, p=0.004) and right (r=0.59, df=9, p=0.07) orbitofrontal regions and between the SCL-90-R anxiety score and the percent change in rCBF in the anterior cingulate (r=0.67, df=9, p=0.03). In sharp contrast, the cocaine-addicted subjects showed an inverse correlation between the aversive response to procaine and percent change in rCBF in the left orbitofrontal (r=–0.71, df=9, p=0.02), left hippocampal (r=–0.63, df=9, p<0.05), and left amygdalar (r=–0.56, df=9, p<0.09) regions as well as between procaine-induced anxiety and percent change in rCBF in the right hippocampus (r=–0.67, df=9, p<0.03) and brainstem (r=–0.75, df=9, p<0.01).