Dopamine receptor alteration in schizophrenia: neuroendocrine evidence

Area of Science:

• Neuroscience
• Psychiatry
• Endocrinology

Background:

• Schizophrenia is hypothesized to involve alterations in central nervous system (CNS) dopaminergic function.
• Growth hormone (hGH) release is sensitive to dopaminergic modulation, making it a potential indicator of CNS dopaminergic activity.

Purpose of the Study:

• To investigate CNS dopaminergic function in schizophrenia by examining hGH responses to dopamine agonists.
• To explore the relationship between hGH response patterns and neuroleptic treatment outcomes in schizophrenia.

Main Methods:

• Administered apomorphine (direct dopamine agonist) and L-Dopa (indirect dopamine agonist) to young male schizophrenic patients and control subjects.
• Measured plasma hGH levels to assess dopaminergic function.
• Compared hGH response distributions between groups and correlated responses with subsequent neuroleptic treatment outcomes.

Main Results:

• Both apomorphine and L-Dopa increased plasma hGH in most subjects.
• A significant difference was observed in hGH response to apomorphine between schizophrenic patients and controls.
• Unusually high hGH response to apomorphine predicted poor neuroleptic response, while low response predicted good response in schizophrenic patients.

Conclusions:

• Variability in hGH response to apomorphine reflects dopamine receptor sensitivity.
• This variability may serve as a biomarker for non-endocrine dopaminergic sensitivity in schizophrenia.
• Findings support theories linking schizophrenia to altered dopamine receptor function, though the specifics remain complex.