Objectives: To evaluate the in vivo effect of apomorphine sublingual versus placebo on cortical and subcortical brain activation during video sexual stimulation.
Methods: Ten patients with psychogenic erectile dysfunction and six potent controls underwent functional magnetic resonance of the brain during video sexual stimulation after the administration of either apomorphine sublingual 4mg or placebo following a randomized, double blind design. Functional magnetic resonance sessions were performed with a 7-day interval.
Results: In potent controls, viewing erotic versus neutral films induced bilateral activations in a network of occipito-parietal and temporal inferior regions, in dorsolateral and premotor frontal cortex, in anterior temporal limbic areas and the thalamus, which were comparable to the patient activations during erotic stimulation in the placebo condition. However, a striking difference was found in patients, who demonstrated a significant and extended activation in the cingulate gyrus, frontal mesial and frontal basal cortex, bilaterally, in comparison with potent controls. These activated neural systems were modulated by apomorphine administration which produced a picture that was similar to the one seen in potent controls. In patients with spychogenic erectile dysfunction apomorphine sublingual caused an increase in the extension of the activated networks, plus additional activation foci in subcortical and deep structures, namely in the nucleus accumbens, hypothalamus and mesencephalon: this activation was greater than that seen with placebo. Interestingly, a down-regulation in the frontal basal and temporal limbic cortex was present as shown by a decrease of functional magnetic resonance imaging signal reflecting a deactivation of these regions.
Conclusions: Apomorphine significantly enhances the activation of cortical and subcortical brain function during video sexual stimulation. Patients with psychogenic erectile dysfunction may have an underlying functional abnormality of the brain acting as a previously unrecognised aetiological factor.