Dopamine agonist switching in Parkinson's disease

Development of Microplatforms to Mimic the In Vivo Architecture of CNS and PNS Physiology and Their Diseases

Understanding the mechanisms that govern nervous tissues function remains a challenge. In vitro two-dimensional (2D) cell culture systems provide a simplistic platform to evaluate systematic investigations but often result in unreliable responses that cannot be translated to pathophysiological settings. Recently, microplatforms have emerged to provide a better approximation of the in vivo scenario with better control over the microenvironment, stimuli and structure. Advances in biomaterials enable the construction of three-dimensional (3D) scaffolds, which combined with microfabrication, allow enhanced biomimicry through precise control of the architecture, cell positioning, fluid flows and electrochemical stimuli. This manuscript reviews, compares and contrasts advances in nervous tissues-on-a-chip models and their applications in neural physiology and disease. Microplatforms used for neuro-glia interactions, neuromuscular junctions (NMJs), blood-brain barrier (BBB) and studies on brain cancer, metastasis and neurodegenerative diseases are addressed. Finally, we highlight challenges that can be addressed with interdisciplinary efforts to achieve a higher degree of biomimicry. Nervous tissue microplatforms provide a powerful tool that is destined to provide a better understanding of neural health and disease.

Low-frequency repetitive transcranial magnetic stimulation and off-phase motor symptoms in Parkinson's disease

Repetitive transcranial magnetic stimulation (rTMS) can modulate cortical excitability and activation and consequently may affect clinical symptoms in neurological conditions characterized by altered motor cortex functions. There are conflicting reports whether low-frequency rTMS has any clinical effects in Parkinson's disease (PD). Ten patients with PD had rTMS (1800 stimuli at just below active motor threshold intensity) at 1Hz rate delivered over the motor cortex for four consecutive days on two separate occasions. On one of these real rTMS was used and on the other sham rTMS (placebo) was used. Evaluations with UPDRS Part 3 (Motor Scale) were done in practically defined off-phase at the baseline and one day after the end of each of the treatment series. Neither total Motor Scale scores nor subscores for axial symptoms, rigidity, bradykinesia, and tremor showed any significant difference. The results do not confirm presence of residual beneficial clinical after-effects of consecutive daily applications of low-frequency rTMS on motor symptoms in PD, at least when 1800 stimuli at subthreshold intensity are applied for four days.

Overnight switching from ergot-derived dopamine agonists to pramipexole in patients with Parkinson's disease: an open preliminary trial in Japan

The aim of this study was to evaluate the safety and tolerability of overnight switching from ergot-derived dopamine agonists such as cabergoline to equivalent doses of pramipexole in patients with Parkinson's disease. The safety of overnight switching to pramipexole from cabergoline, which has a long plasma half-life and may cause dopaminergic excess after switchover, has not been established. Twenty-two consecutive patients with Parkinson's disease were included, 18 of them on cabergoline treatment. Patients were assessed with the Unified Parkinson's Disease Rating Scale (UPDRS) given just prior to switching as well as after 2, 4, 8, and 12 weeks of treatment. Eight patients (36.4%) experienced adverse events, of whom two were withdrawn from the study. Generally, however, significant improvement in the UPDRS was obtained after 2 weeks and improvement was maintained up to 12 weeks of treatment. Therefore, our study showed that overnight switching from ergot-derived dopamine agonists including cabergoline to dose-equivalent pramipexole was safe when associated with good patient compliance.

Changing dopamine agonist treatment in Parkinson's disease: experiences with switching to pramipexole

1202 patients suffering from Parkinson's disease switched from other dopamine agonists to pramipexole under open conditions either abruptly or in an overlapping, gradual manner. Mostly insufficient effectiveness motivated the switch. The investigators gave equal preference to either an abrupt or an overlapping switch to pramipexole in this observational study. There was a tendency in favour of the overlapping switch procedure in those patients who were on a relatively higher dose of a dopamine agonist before the switch. The switch was performed because the investigators expected the effect of pramipexole on tremor, motor functions and depression/anhedonia to be better compared with previous dopamine agonists. The main reasons for switching to pramipexole (anti-tremor effect, anti-depressive/anti-anhedonic effect) as given by the physicians at baseline came up to expectations. The switch to pramipexole mostly yielded further improvements irrespective of the mode of switching.