Urinary homovanillic acid and c-AMP in drug-free Parkinson patients: effect of L-dopa treatment.

Homovanillic acid (HVA) and adenosine-3',5'-monophosphate (c-AMP) were estimated in the morning urine of 33 drug-free Parkinson patients and 25 hospitalized controls. 21 of the patients had never been treated; the mean duration of the illness was 2.6 years. Parkinson patients excreted more HVA and less c-AMP compared to the controls; it was the subgroup with tremor as the main symptom that caused this difference, while the subgroups with akinesia or rigidity as the main symptom has values not significantly different from those of the control group. 22 of the patients were studied again after 2 weeks of treatment with L-dopa + decarboxylase inhibitor. HVA excretion increased 20-fold while c-AMP excretion decreased 9% (p less 0.05). The reduction in the c-AMP excretion was observed only in the subgroups with akinesia or rigidity as the main symptom (p less 0.025), while there was no change in the tremor group where the pretreatment c-AMP was low. The results indicate a difference in the dopamine receptor sensitivities in the subgroups of the patients.