Down-regulation of central dopamine receptors in schizophrenia.

CSF homovanillic acid (HVA) levels reflecting central dopamine release and apomorphine-stimulated human growth hormone (HGH) secretion reflecting central dopamine receptor activity were concomitantly determined in 20 schizophrenic patients. There was a strong negative correlation between HVA and HGH levels: high dopamine release was associated with lower HGH responses to dopamine receptor activation by apomorphine. Studies are reviewed which suggest that the presently observed relationship reflects release-mediated down-regulation of central D2 receptors, the dopamine receptor subtype associated with the antipsychotic properties of neuroleptic medication.