Modulation of normal and pathologic motoneuron activity during sleep: insights from the neurology clinic, Parkinson's disease, and comments on parkinsonian-related sleepiness

Selective serotonin 2A receptor antagonism attenuates the effects of amphetamine on arousal and dopamine overflow in non-human primates

The objective of the present study was to further elucidate the mechanisms involved in the wake-promoting effects of psychomotor stimulants. Many previous studies have tightly linked the effects of stimulants to dopamine neurotransmission, and some studies indicate that serotonin 2A receptors modulate these effects. However, the role of dopamine in arousal is controversial, most notably because dopamine neurons do not change firing rates across arousal states. In the present study, we examined the wake-promoting effects of the dopamine-releaser amphetamine using non-invasive telemetric monitoring. These effects were evaluated in rhesus monkeys as a laboratory animal model with high translational relevance for human disorders of sleep and arousal. To evaluate the role of dopamine in the wake-promoting effects of amphetamine, we used in vivo microdialysis targeting the caudate nucleus, as this approach provides clearly interpretable measures of presynaptic dopamine release. This is beneficial in the present context because some of the inconsistencies between previous studies examining the role of dopamine in arousal may be related to differences between postsynaptic dopamine receptors. We found that amphetamine significantly and dose-dependently increased arousal at doses that engendered higher extracellular dopamine levels. Moreover, antagonism of serotonin 2A receptors attenuated the effects of amphetamine on both wakefulness and dopamine overflow. These findings further elucidate the role of dopamine and serotonin 2A receptors in arousal, and they suggest that increased dopamine neurotransmission may be necessary for the wake-promoting effects of amphetamine, and possibly other stimulants.

Improvements in nocturnal symptoms with ropinirole prolonged release in patients with advanced Parkinson's disease

BACKGROUND

The 24-week, double-blind Efficacy and Safety Evaluation in PD-Adjunct (EASE-PD Adjunct) study randomized patients with advanced Parkinson's disease (PD) suboptimally controlled with levodopa to once-daily placebo or adjunctive ropinirole prolonged release (2-24 mg/day). We investigated the effect of ropinirole prolonged release on nocturnal symptoms in these patients.

METHODS

Total and grouped item PD Sleep Scale (PDSS) scores were analyzed post hoc in patients with baseline PDSS total scores ≤ 100 (troublesome nocturnal symptoms) and >100.

RESULTS

Baseline PDSS total score was ≤ 100 in 93 of 198 (47%) and 89 of 189 (47%) patients receiving ropinirole prolonged release and placebo, respectively; this subgroup displayed evidence at baseline of greater daily awake 'off' time, reduced night-time sleep and worse quality of life, than the PDSS >100 subgroup. Significant improvements with ropinirole prolonged release versus placebo in PDSS score from baseline to Week 24 last observation carried forward were observed for those with baseline PDSS ≤ 100 [adjusted mean treatment difference 9.0 (95% CI: 2.76, 15.33; P = 0.0051)], but not >100. The PDSS ≤ 100 subgroup demonstrated treatment benefits for PDSS groupings of motor symptoms on waking and global quality of sleep. Changes in daytime sleepiness were similar between treatment groups. The PDSS >100 subgroup demonstrated significant treatment benefit for global quality of sleep. The unadjusted odds ratio for a positive response with ropinirole prolonged release relative to placebo, for the PDSS ≤ 100 subgroup, was 2.90 (95% CI: 1.42, 5.95, P = 0.004).

CONCLUSIONS

Once-daily ropinirole prolonged release improves nocturnal symptoms in patients with advanced PD not optimally controlled with levodopa who suffer troublesome nocturnal disturbance.