BACKGROUND: The pathophysiologic mechanisms underlying parkinsonian tremor remain unclear. The response to dopaminergic treatment is variable and nondopaminergic mechanisms may play a role in tremor generation. Midbrain raphe 5-HT(1A) binding provides a functional measure of serotonergic system integrity. With PET, the aim of this study was to examine regional cerebral (11)C-WAY 100635 binding to 5-HT(1A) receptors in patients with PD and to correlate it with severity of tremor. METHODS: (11)C-WAY 100635 PET was performed on 23 patients with PD and eight age-matched healthy volunteers. Brain 5-HT(1A) receptor binding was computed using compartmental modeling with a cerebellar reference tissue input function. RESULTS: The authors found mean 27% reduction in the midbrain raphe 5-HT(1A) binding potential in patients with PD compared to healthy volunteers (p < 0.001). They also showed that Unified Parkinson's Disease Rating Scale composite tremor scores, but not rigidity or bradykinesia, correlate with 5-HT(1A) binding in the raphe (p < 0.01). CONCLUSIONS: These findings support previous indirect evidence that serotonergic neurotransmission is decreased in PD in vivo. The authors hypothesize that the reduction in raphe 5-HT(1A) binding represents receptor dysfunction or loss of cell bodies due to Lewy body degeneration in PD, or both. An association between 5-HT(1A) receptor availability in the raphe and severity of parkinsonian tremor was also found.
BACKGROUND: The pathophysiologic mechanisms underlying parkinsonian tremor remain unclear. The response to dopaminergic treatment is variable and nondopaminergic mechanisms may play a role in tremor generation. Midbrain raphe 5-HT(1A) binding provides a functional measure of serotonergic system integrity. With PET, the aim of this study was to examine regional cerebral (11)C-WAY 100635 binding to 5-HT(1A) receptors in patients with PD and to correlate it with severity of tremor. METHODS: (11)C-WAY 100635 PET was performed on 23 patients with PD and eight age-matched healthy volunteers. Brain 5-HT(1A) receptor binding was computed using compartmental modeling with a cerebellar reference tissue input function. RESULTS: The authors found mean 27% reduction in the midbrain raphe 5-HT(1A) binding potential in patients with PD compared to healthy volunteers (p < 0.001). They also showed that Unified Parkinson's Disease Rating Scale composite tremor scores, but not rigidity or bradykinesia, correlate with 5-HT(1A) binding in the raphe (p < 0.01). CONCLUSIONS: These findings support previous indirect evidence that serotonergic neurotransmission is decreased in PD in vivo. The authors hypothesize that the reduction in raphe 5-HT(1A) binding represents receptor dysfunction or loss of cell bodies due to Lewy body degeneration in PD, or both. An association between 5-HT(1A) receptor availability in the raphe and severity of parkinsonian tremor was also found.
Authors: V Caretti; D Stoffers; A Winogrodzka; I-U Isaias; G Costantino; G Pezzoli; C Ferrarese; A Antonini; E-Ch Wolters; J Booij Journal: J Neural Transm (Vienna) Date: 2008-03-12 Impact factor: 3.575