Serotonergic neurotransmission in early Parkinson's disease: a pilot study to assess implications for depression in this disorder.
OBJECTIVE
Depression, a disease usually accompanied by a serotonergic deficit, has been observed in about 40% of patients suffering from Parkinson's disease (PD). Thus, a serotonergic dysfunction in PD can be assumed. We aimed to investigate the interaction between serotonergic (5-HT) and dopaminergic activity in early PD. We hypothesized a serotonergic as well as a dopaminergic deficit in PD patients. We also assumed a correlation between these neurotransmitters indicating a relationship between dopaminergic and serotonergic function in PD.


METHODS
Nine unmedicated PD patients before and 12 weeks after L-dopa treatment and nine healthy subjects were examined using the loudness dependence of auditory evoked potentials (LDAEP), a promising indicator of central serotonergic function. Dopaminergic transporters (DAT) were collected using (123)I-FP-CIT and single photon emission computer tomography (SPECT). LDAEP values were correlated with (123)I-FP-CIT SPECT data.


RESULTS
A significant difference between LDAEP of controls and patients (P= 0.05) suggested lower serotonergic activity in PD. Twelve weeks after initiation of L-dopa treatment this difference was lost between patients and controls (P= 0.20). There was a trend towards a correlation between LDAEP and DAT (r= 0.65; P = 0.057) of the unmedicated patients, suggesting a low serotonergic activity may be related to a dopamine deficit in PD.


CONCLUSIONS
Our results support the hypothesis that serotonergic neurotransmission is decreased in untreated PD and suggest that a low serotonergic activity may be related to the dopamine pathology in PD. This could be related to the high prevalence of depression in PD.
Beucke
Jan C
JC
Department of Clinical Psychology, Humboldt University, Berlin, Germany.
Uhl
Idun
I
Plotkin
Michail
M
Winter
Christine
C
Assion
Hans-Jörg
HJ
Endrass
Tanja
T
Amthauer
Holger
H
Kupsch
Andreas
A
Juckel
Georg
G
D000368:Aged; D003866:Depressive Disorder / Q000150:complications / Q000378:metabolism*; D050483:Dopamine Plasma Membrane Transport Proteins / Q000378:metabolism; D005072:Evoked Potentials, Auditory; D005260:Female; D006801:Humans; D007980:Levodopa / Q000627:therapeutic use; D008297:Male; D026901:Membrane Transport Proteins / Q000378:metabolism; D008875:Middle Aged; D010300:Parkinson Disease / Q000150:complications / Q000188:drug therapy / Q000378:metabolism*; D010865:Pilot Projects; D011985:Receptors, Serotonin / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism*; D009435:Synaptic Transmission; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods
D050483:Dopamine Plasma Membrane Transport Proteins; D026901:Membrane Transport Proteins; D011985:Receptors, Serotonin; D012701:Serotonin; D007980:Levodopa