Purpose: The present study investigates whether cerebral activation during visually evoked sexual arousal is different in patients with erectile dysfunction (ED) compared to the known pattern observed in healthy men, and additionally how cerebral activity during visual sexual stimulation is modified by treatment with apomorphine SL and whether the observed cerebral activity correlates with penile rigidity.
Patients and methods: Cerebral activity was measured before and after treatment in 12 patients with erectile dysfunction randomised to receive either apomorphine SL or placebo using [15O]H(2)O-PET. Two PET scans were performed prior to administration of the study medication, the first after a neutral audiovisual stimulus and the second following a sexually stimulating audiovisual presentation. After receiving the study medication, patients were subjected to two additional scans each preceded by a sexually stimulating stimulus. Penile rigidity was assessed with the RigiScan device. Evaluation for significant regional cerebral activation was performed using statistical parametric mapping (SPM99).
Results: Cerebral activity increased significantly after the sexually stimulating video sequence compared to the neutral one in the inferior frontal cortex (Brodmann areas [BA] 47, 10, 11) and the rostral anterior cingulate (BA 32), and cerebral activity was observed to decrease in both inferior temporal cortices (BA 20). 4 out of 6 patients showed significant penile rigidity after apomorphine SL and in none of those receiving placebo. Apomorphine SL was observed to increase cerebral activity in the right superior prefrontal area (BA 6) that was not seen with placebo, while neither apomorphine SL nor placebo produced decreased cerebral activity. Penile rigidity correlated with increased cerebral activity in the anterior cingulum and right prefrontal cortex, and with decreased activity in the temporal cortex.
Conclusions: In patients with erectile dysfunction, the pattern of increased and decreased cerebral activity in response to visual sexual stimuli in this study is similar to that reported in the literature in healthy men. Apomorphine SL appears to induce additional cerebral activity in the right prefrontal cortex, an area previously shown to be associated with sexual arousal in male volunteers during orgasm. This increased cerebral activity was associated with penile rigidity, further supporting the conclusion that apomorphine SL improves erectile function in men with ED by enhancing the natural central erectile signals that normally occur during sexual stimulation.