Patient-driven N-of-1 in Parkinson's Disease. Lessons Learned from a Placebo-controlled Study of the Effect of Nicotine on Dyskinesia.

BACKGROUND: New insights and knowledge in biomedical science often come from observation and experimentation. Methods traditionally used include self-experimentation, case reports, randomised controlled trials, and N-of-1 studies. Technological advances have lead to an increasing number of individuals and patients engaging in self-tracking. We use the term patient-driven N-of-1 for self-tracking performed with the explicit intention to disseminate the results by academic publishing. OBJECTIVES: The aim of the study was to: 1) explore the potential role for patient-driven N-of-1 studies as a tool for improving self-management in Parkinson's disease (PD) using the example of managing levodopa-induced dyskinesia (LID) with nicotine, and 2) based on this example; identify some specific challenges of patient-driven N-of-1 studies. METHODS: We used a placebo controlled patient-driven N-of-1 study with nicotine administered via e-cigarette to treat LID. The first author initiated and conducted the experiment on herself and noted her observations. The evaluations of the potential of N-of-1 for improving self-management of PD as well as the effects of nicotine on dyskinesia were based on the perception of the subject. During the planning and undertaking of the experiment, notes were made to identify challenges specific to patient-driven N-of-1 studies. RESULTS: The subject was able to distinguish a decrease of her LID from nicotine but no effect from placebo. The main challenges of patient-driven N-of-1 studies were identified to be associated with planning of the study, recruiting a suitable research team, making sure the data collection is optimal, analysis of data, and publication of results. CONCLUSIONS: Our study indicates that nicotine administered via e-cigarette may have an effect on levodopa-induced dyskinesia in individual patients with PD. The main contribution is however highlighting the work done by patients on a daily basis for understanding their conditions and conducting self-tracking experiments. More work is needed to further develop methods around patient-driven N-of-1 studies for PD.

Drugs of abuse and Parkinson's disease.

The term "drug of abuse" is highly contextual. What constitutes a drug of abuse for one population of patients does not for another. It is therefore important to examine the needs of the patient population to properly assess the status of drugs of abuse. The focus of this article is on the bidirectional relationship between patients and drug abuse. In this paper we will introduce the dopaminergic systems of the brain in Parkinson's and the influence of antiparkinsonian drugs upon them before discussing this synergy of condition and medication as fertile ground for drug abuse. We will then examine the relationship between drugs of abuse and Parkinson's, both beneficial and deleterious. In summary we will draw the different strands together and speculate on the future merit of current drugs of abuse as treatments for Parkinson's disease.

What Engineering Technology Could Do for Quality of Life in Parkinson's Disease: A Review of Current Needs and Opportunities.

Parkinson's disease (PD) involves well-known motor symptoms such as tremor, rigidity, bradykinesia, and altered gait, but there are also nonlocomotory motor symptoms (e.g., changes in handwriting and speech) and even nonmotor symptoms (e.g., disrupted sleep, depression) that can be measured, monitored, and possibly better managed through activity-based monitoring technologies. This will enhance quality of life (QoL) in PD through improved self-monitoring and also provide information that could be shared with a healthcare provider to help better manage treatment. Until recently, nonmotor symptoms ("soft signs") had been generally overlooked in clinical management, yet these are of primary importance to patients and their QoL. Day-to-day variability of the condition, the high variability in symptoms between patients, and the isolated snapshots of a patient in periodic clinic visits make better monitoring essential to the proper management of PD. Continuously monitored patterns of activity, social interactions, and daily activities could provide a rich source of information on status changes, guiding self-correction and clinical management. The same tools can be useful in earlier detection of PD and will improve clinical studies. Remote medical communications in the form of telemedicine, sophisticated tracking of medication use, and assistive technologies that directly compensate for disease-related challenges are examples of other near-term technology solutions to PD problems. Ultimately, a sensor technology is not good if it is not used. The Parkinson's community is a sophisticated early adopter of useful technologies and a group for which engineers can provide near-term gratifying benefits.

Simultaneous real-time amperometric measurement of catecholamines and serotonin at carbon fibre 'dident' microelectrodes.

Amperometry allows real-time measurement of in vivo electrochemical signals, albeit with no capacity to identify the constituents of the signal. In the present study, differential amperometry was used to monitor catecholamine and serotonin (5-HT) simultaneously at the same location. 'Dident' carbon fibre microelectrodes (microelectrodes with two working electrodes in a single assembly) were constructed and coated with Nafion to prevent poisoning on contact with brain tissue. One electrode (channel A) was held at +200 mV versus Ag/AgCl to monitor catecholamines selectively. This potential is too low to oxidise 5-HT. The second electrode (channel B), recording faradaic current at +500 mV versus Ag/AgCl, measured the sum of catecholamine and 5-HT oxidation. The 5-HT current component was the difference of channel B minus channel A. With appropriate balancing of the two channels, it is possible to record catecholamines and 5-HT simultaneously at the same dident microelectrode. Examples of measurements in striatum, cortex and locus coeruleus are shown.

Stereoselective effects of ketamine on dopamine, serotonin and noradrenaline release and uptake in rat brain slices.

Ketamine (2-(2-chlorophenyl)-(1-methylamino)-cyclohexanone) is a rapid-acting dissociative general anaesthetic whose hallucinogenic properties have made it a popular drug of abuse. Ketamine comprises two optical isomers, with differing pharmacology. In the present study, the effects of (+)- and (-)-ketamine on stimulated efflux and reuptake of dopamine (DA), noradrenaline (NA) and serotonin (5-HT) were compared in isolated superfused slices of the rat caudatoputamen (CPu), ventral bed nucleus of the stria terminalis (BSTV) or dorsal raphe nucleus (DRN), respectively. Monoamine efflux was elicited by local electrical stimulation (20 pulses, 100 Hz trains) at tungsten microelectrodes and measured at adjacent carbon fibre microelectrodes using fast cyclic voltammetry (FCV). In CPu (+)-ketamine increased stimulated DA efflux and slowed DA reuptake in a concentration-dependent manner (25-200 microM). At 100 microM (+)-ketamine increased DA efflux by 109+/-20% (mean+/-S.E.M., n=13) of control values after 30 min (P<0.001 versus control) and prolonged uptake half-time (t(1/2)) by 76+/-38% (n=9, P<0.001) of control. In contrast (-)-ketamine (100 microM) had no effect on DA efflux or uptake. In DRN, both isomers (100 microM) increased stimulated 5-HT efflux. (-)-Ketamine had a larger effect (P<0.001), an 88+/-15% increase in 5-HT efflux (n=9) versus 46+/-10% (n=8) for the (+)-isomer. The isomers had similar effects on 5-HT uptake, increasing t(1/2) by approximately 200%. No evidence of stereospecificity was seen in BSTV: both isomers had small effects (+)- and (-)-ketamine (100 microM) increasing NA efflux by 43+/-10% (n=7, P<0.001) and 29+/-8% (n=7, P<0.001), respectively. The isomers also had identical effects on NA uptake, each increasing uptake t(1/2) by approximately 100%. In summary, our data show that the optical isomers of ketamine have strikingly different stereospecificity for the monoamine systems and one might predict, therefore, a different psychotomimetic potential.

Different alpha(2) adrenoceptor subtypes control noradrenaline release and cell firing in the locus coeruleus of wildtype and monoamine oxidase-A knockout mice.

In this study, we investigated which subtype(s) of alpha(2)-adrenoceptor control stimulated noradrenaline (NA) release and noradrenergic cell firing in the locus coeruleus (LC) of monoamine oxidase-A knockout (MAO-A KO) and C3H/HeJ wildtype mice. On short stimulus trains (10 pulses, 200 Hz), the alpha(2) agonist dexmedetomidine (10 nm) reduced NA efflux by 78 +/- 8% and 51 +/- 8% in wildtype and MAO-A KO mice, respectively. In both strains, BRL 44408 (100 nm) and ARC 239 (100 nm) each partially blocked the effect of dexmedetomidine. In MAO-A KO mice, BRL 44408 (100 nm) increased evoked NA efflux on short trains while ARC 239 (100 nm) had no effect. The two antagonists in combination increased NA efflux (by 81 +/- 34%, P < 0.001), significantly more than by BRL 44408 alone. Conversely, in wildtype mice, the alpha2-adrenoceptor antagonists did not significantly increase LC NA efflux. On long stimuli (30 pulses, 10 Hz), NA efflux was increased by BRL 44408 (P < 0.001) but not by ARC 239. The effect of BRL 44408 was significantly greater in MAO-A KO than wildtype mice (208 +/- 43% vs. 113 +/- 31% increase, P < 0.001). When we examined noradrenergic cell firing, we found that dexmedetomidine inhibited LC cell firing in both strains with comparable EC(50) values (2-5 nm), although E(max) was significantly lower in MAO-A KO mice (P < 0.001). The agonist effect was antagonized by BRL 44408 (P < 0.001) in wildtype but not in MAO-A KO mice, with a pK(B) of 7.75. ARC 239 had no effect on the agonist response in either strain. A combination of the antagonists was no more effective than BRL 44408 alone (in wildtypes) and had no effect in MAO-A KO mice. Neither BRL 44408 nor ARC 239 affected basal LC cell firing in wildtype or MAO-A KO mice. Collectively, these results suggest that, analogous to other monoamine cell groups, there are differences in the autoreceptor populations controlling NA efflux and LC cell firing and that important differences exist between MAO-A KO and wildtype mice.

Ectopic serotonin accumulation and efflux in rat mesencephalic slices after prior tissue 'radiolabelling'.

Radiolabelling of brain tissue has long been used to facilitate detection of transmitter efflux, on the assumption that egress of tritiated monoamines reflects that of the endogenous transmitter. The present study tested the hypothesis that the application of exogenous serotonin (5-HT) to mesencephalic slices, in the manner used during a typical radiolabelling protocol, leads to efflux of 5-HT from physiologically inappropriate loci such as other non-serotonergic neurones. We used fast cyclic voltammetry (FCV) to determine the effect of tissue pre-incubation with 5-HT on electrically-stimulated 5-HT efflux and reuptake in rat mesencephalic slices. Seven subregions were studied, including the dorsal raphe nucleus (DRN), dorsomedial periaqueductal grey (PAGdm) and the oral part of the pontine reticular nucleus (PnO). In control slices (pre-incubated without 5-HT), stimulated 5-HT efflux was only detectable in DRN, PAGdm and occasionally in PnO. In slices incubated in 5-HT (100nM) for 30min, stimulated 5-HT efflux was detected in all seven subregions studied. In such slices, citalopram (75nM) increased efflux and reuptake t(1/2) in DRN to 201+/-21 and 487+/-117% of pre-drug values (P<0.05) but had no significant effect on either measure in PnO. The 5-HT1 autoreceptor agonist, 5-carboxamidotryptamine (5-CT, 100nM) decreased efflux in DRN by 54+/-6% (P<0.05), but was without effect (10+/-14%) in PnO. The present results show that pre-incubation in 5-HT allows stimulated 5-HT efflux from regions of the mesencephalon other than DRN and PAGdm. This stimulated 5-HT efflux is apparently not influenced by 5-HT transporters or 5-HT1 autoreceptors, suggesting that efflux is ectopic, an artefact of the pre-incubation process. In summary, incubation of rat mesencephalic tissue in 5-HT, in the manner of a typical radiolabelling protocol, results in stimulated 5-HT efflux from non-physiological sites. The results of such transmitter efflux studies should thus be interpreted with caution.

Presynaptic control of striatal dopamine neurotransmission in adult vesicular monoamine transporter 2 (VMAT2) mutant mice.

The vesicular monoamine transporter 2 (VMAT2) plays a pivotal role in regulating the size of vesicular and cytosolic dopamine (DA) storage pools within the CNS, and can thus influence extracellular DA neurotransmission. Transgenic mice have been generated with a dramatically reduced (by approximately 95%) expression of the VMAT2 gene which, unlike complete knockout lines, survive into adulthood. We compared the pre-synaptic regulation of both impulse-dependent (exocytotic) and carrier-mediated (via reversal of the DA transporter, DAT) DA release in the dorsolateral caudate putamen (CPu) of striatal slices derived from adult homozygous VMAT2 mutant and wild-type mice using fast cyclic voltammetry. Impulse-dependent DA release, evoked by a single electrical pulse, was lower in homozygous (116 nm) than wild-type mice (351 nm) indicating smaller vesicular DA stores, an observation supported by the evanescent effect of amfonelic acid (300 nm) in homozygous mice. Amphetamine (2 microm) increased extracellular DA via DAT reversal in both wild-type (by 459 nm) and VMAT2 mutant (by 168 nm, p < 0.01 vs. wild-type) mice. In both cases, the effect was blocked by the DAT inhibitor GBR12935 (1 microm). Simultaneously, amphetamine decreased impulse-dependent DA release, albeit less in homozygous (by 55%) than in wild-type (by 78%) mice. In wild-types, this decrement was largely reversed by GBR12935 but not by the D2/D3 autoreceptor antagonist (-)sulpiride (1 microm). Conversely, in homozygous VMAT2 mutant mice, it was attenuated by (-)sulpiride but not GBR12935. The D2/D3 receptor agonist quinpirole inhibited impulse-dependent DA release with a lower EC50 value in homozygous mice (12 nm) compared with wild-types (34 nm), indicating the compensatory presence of functionally supersensitive release-regulating autoreceptors. However, analysis of DA reuptake kinetics obtained in the absence and presence of DAT blockade (by cocaine and amfonelic acid) revealed only minor differences in DAT functionality. These results demonstrate that impaired vesicular DA storage constrains extracellular DA levels in the dorsolateral CPu whether induced by either impulse-dependent or carrier-mediated mechanisms and that the relative importance of the DAT and terminal autoreceptors as control mechanisms in the actions of amphetamine are reversed in VMAT2 mutant mice.

An assessment of the cerebroprotective potential of volatile anaesthetics using two independent methods in an in vitro model of cerebral ischaemia.

Previous studies using a rat brain slice model of cerebral 'ischaemia' (hypoxia and hypoglycaemia) have suggested that volatile anaesthetics may have cerebroprotective potential. In this study, we tested the cerebroprotective profile of four volatile anaesthetics in this model by two independent means: voltammetric measurement of 'ischaemia'-induced dopamine (DA) release and post-'ischaemic' tissue staining with 2,3,5-triphenyltetrazolium chloride (TTC). 'Ischaemia' caused a characteristic pattern of DA release. Halothane, isoflurane and enflurane did not affect the time from onset of 'ischaemia' to the initiation of DA release. However, all three volatile agents significantly increased (P<0.01, P<0.05, P<0.001, respectively) the time taken for 'ischaemia'-induced DA release to reach maximum and reduced the rate of DA release. Enflurane, unlike halothane or isoflurane, reduced the maximal extracellular DA concentration induced by 'ischaemia' (P<0.01). The effects of sevoflurane were inconsistent. At the higher concentrations used, the volatile anaesthetics frequently changed the character of DA release from monophasic to biphasic, an effect only previously seen in this model with Na(+) channel blockers. 'Ischaemia' also diminished the subsequent level of tissue staining with TTC. When the effects of the volatile agents were analysed by TTC staining, only enflurane showed any cerebroprotective effects and these were limited to the striatum (P<0.01). High concentrations of halothane, isoflurane and enflurane appeared to have some 'toxic' effects, reducing TTC staining in control slices. In summary, we do not find any consistent evidence that volatile anaesthetics are cerebroprotective in this model.

Altered presynaptic function in monoaminergic neurons of monoamine oxidase-A knockout mice.

Monoamine oxidase-A knockout (MAO-A KO) mice have elevated brain serotonin (5-HT) and noradrenaline (NA) levels, and one would therefore anticipate increased monoamine release and compensatory changes in other aspects of presynaptic monoamine function. In this study we used voltammetry in brain slices from the locus coeruleus (LC), dorsal raphe (DRN) and striatum (CPu) in 7-week-old MAO-A KO and C3H control mice to measure stimulated monoamine efflux and its control by amine transporters and autoreceptors. In LC, peak NA efflux on stimulation (99 pulses, 100 Hz) was higher in MAO-A KO than C3H mice (938 +/- 58 nm cf. 511 +/- 42 nm; P < 0.001). The NA uptake half time (t(1/2)) was longer in MAO-A KO than in C3H mice (6.0 +/- 0.9 s cf. 1.9 +/- 0.3 s; P < 0.001) and the selective NA reuptake inhibitor desipramine (50 nm) had a smaller effect in MAO-A KO mice. NA transporter binding was significantly lower in the LC of MAO-A KO mice compared to C3H controls (P < 0.01) but not in the DRN. The alpha 2 agonist dexmedetomidine (10 nm) decreased stimulated NA efflux more in C3H than in MAO-A KO mice (73.3% cf. 29.6% inhibition, P < 0.001). In DRN, peak 5-HT efflux on stimulation (99 pulses, 100 Hz) was greater (P < 0.01) in MAO-A KO (262 +/- 44 nm) than C3H mice (157 +/- 16 nm). Moreover, 5-HT uptake t(1/2) was longer (P < 0.05) in MAO-A KO than in C3H mice (8.8 +/- 1.1 s cf. 4.9 +/- 0.6 s, P < 0.05) and the effect of citalopram (75 nm) was attenuated in MAO-A KOs. Serotonin transporter binding was also lower in both the DRN and LC of MAO-A KO mice. The 5-HT(1A) agonist 8-OH-DPAT (1 microm) decreased 5-HT efflux more in C3H than in MAO-A KO mice (38.3% inhibition cf. 21.6%, P < 0.001). In contrast, there were no significant differences between MAO-A KO and C3H mice in CPu dopamine efflux and uptake and the effect of the D(2/3) agonist quinpirole was similar in the two strains. In summary, MAO-A KO mice show major dysregulation of monoaminergic presynaptic mechanisms such as autoreceptor control and transporter kinetics.

Time window of autoreceptor-mediated inhibition of limbic and striatal dopamine release.

Forebrain dopamine release is under the local control of D2 family (D2 and D3) autoreceptors. In this study, autoreceptor-mediated modulation of forebrain dopamine release was investigated using amperometry in brain slices following local electrical stimulation. 350 microm-thick slices of nucleus accumbens or dorsolateral neostriatum were prepared from male Wistar rats (150-200 g) and superfused with artificial cerebrospinal fluid at 32 degrees C. Dopamine release was evoked by electrical pulses (0.1 ms, 10 mA) across bipolar tungsten stimulating electrodes and measured at carbon fibre microelectrodes using fixed potential amperometry (+300 mV vs. Ag/AgCl). Peak dopamine release on stimulation (single pulse) was 0.75 microM (neostriatum) and 1.37 microM (nucleus accumbens). Metoclopramide (1 microM) had no significant effect on DA efflux from a single pulse in either region. Using paired pulse stimuli, dopamine release on the second pulse varied according to the interval between the two pulses. At very long intervals (>20 sec), dopamine release was similar to that for the first pulse. At shorter intervals, dopamine efflux was attenuated. Metoclopramide had no effect on second pulse dopamine release when the pulse was applied at short (<0.1 sec) or long (>5.0 sec) intervals after the first. At intermediate intervals, metoclopramide significantly increased second pulse dopamine release. The peak dopamine autoreceptor effect occurred at approximately 550 ms in neostriatum and approximately 700 ms in nucleus accumbens. The onset time is due both to diffusion of dopamine from the release sites to the autoreceptors and receptor-effector mechanisms. These findings may have implications for the local control of forebrain dopamine function in physiological and pathological states.