LAUSR

Background: Patients with first-episode psychosis respond well to initial antipsychotic treatment, but among patients experiencing a relapse of psychosis, the response rate falls to approximately 30%. The mechanism of this discrepancy has not been clarified, but the development of dopamine supersensitivity psychosis with the underlying up-regulation of post-synaptic dopamine D2 receptors could be involved in this lesser response. It is uncertain whether elevated dopamine synthesis and release occurs in patients with dopamine supersensitivity psychosis, in contrast to those with first-episode psychosis. Patients and methods: We examined a first-episode psychosis group (n=6) and a chronic schizophrenia group, i.e. patients experiencing relapse (n=23) including those who relapsed due to dopamine supersensitivity psychosis (n=18). Following the initiation of treatment, we measured the patients’ blood concentrations of homovanillic acid and 3-methoxy-4-hydroxyphenylglycol at two weeks and four weeks after the baseline measurements. Results: The first-episode psychosis group tended to show decreased homovanillic acid, accompanied by an improvement of symptoms. The chronic schizophrenia group showed no alteration of homovanillic acid or 3-methoxy-4-hydroxyphenylglycol over the treatment period. These results were the same in the dopamine supersensitivity psychosis patients alone. Conclusions: Our findings suggest that unlike first-episode psychosis, the release of dopamine from presynaptic neurons did not increase in relapse episodes in the patients with dopamine supersensitivity psychosis. This indirectly indicates that the development of supersensitivity of post-synapse dopamine D2 receptor is involved in relapse in dopamine supersensitivity psychosis patients.