Clinical evidence for multiple dopamine receptors in man

The dopaminergic receptors in man appear to have much the same diversity and similarity as those present in laboratory animals. Most but not all, dopamine (DA) receptor blocking drugs have comparable effects on a variety of behaviors or chemical indices of anti-dopaminergic activity at postsynaptic DA receptors [antipsychotic action, extrapyramidal side effects, anti-emesis, increased cerebrospinal fluid (CSF) homovanillac acid (HVA), or serum prolactin stimulation] suggesting similar DA receptors in the striatal, limbic and cortical brain regions and the pituitary. Several drugs are exceptions, e.g., clozapine and sulpiride, raising the possibility these drugs affect other DA receptors or act via non-dopaminergic mechanisms. The presence of autoreceptors on striatal, limbic or cortical DA neurons is supported by a variety of clinical studies involving apomorphine, piribedil or bromocriptine administration to normal controls, psychotic patients and patients with Parkinson's disease, tardive dyskinesia or Huntington's chorea. [³H]-Spiroperidol binding studies also suggest different DA receptors in the human cortex and caudate. A DA-sensitive adenylate cyclase has been found in the human brain. Glial DA receptors have been proposed.