The early clinical symptoms of Parkinson's disease (PD) may be difficult to perceive and are frequently overlooked. Moreover, there is evidence that degeneration of dopaminergic neurons in the substantia nigra pars compacta begins much in advance with respect to the onset of symptoms. Thus, interest has focused on the identification of biological or instrumental tools that may contribute to the early diagnosis of PD. with the aim to introduce neuroprotective therapies early during the course of illness. Dopamine plays a role in the interactions between the nervous and immune systems. Dopamine receptors have been identified in peripheral blood lymphocytes (PBL) and it has been shown that D3 receptor mRNA is reduced in PBL in PD. Moreover, there is evidence that these cells synthesize catecholamines. In the present study we further investigated PBL dopamine system in PD by measuring the content of dopamine and the immunoreactivity for tyrosine hydroxylase. Dopamine content was measured by HPCL, whereas tyrosine hydroxylase immunoreactivity was detected by semiquantitative immunocytochemistry. PBL from early PD patients (n = 12) have significantly lower amounts of dopamine and reduced tyrosine hydroxylase immunoreactivity as compared to healthy subjects. These changes were not affected by therapy with direct dopamine agonists (n = 8). Tyrosine hydroxylase immunoreactivity was decreased also in PD patients under therapy with levodopa. Conversely, PD patients treated with levodopa (n = 6) had very high levels of dopamine in PBL. These findings suggest the impairment of endogenous dopamine system in PBL in the early clinical stages of PD. If confirmed on a larger set of patients, these findings would indicate that PBL represent a useful tool with which to identify precociously the impairment of dopamine function in PD.
|Number of pages||1|
|Journal||Italian Journal of Neurological Sciences|
|Publication status||Published - 1999|
ASJC Scopus subject areas
- Clinical Neurology