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Stereptactic microdialysis of the basal ganglia in Parkinson's disease
Linköpings universitet, Institutionen för klinisk och experimentell medicin, Neurokirurgi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Sinnescentrum, Neurokirurgiska kliniken US.
Linköpings universitet, Institutionen för klinisk och experimentell medicin, Klinisk kemi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Diagnostikcentrum, Klinisk kemi.
Linköpings universitet, Institutionen för klinisk och experimentell medicin, Klinisk kemi. Linköpings universitet, Hälsouniversitetet.
Östergötlands Läns Landsting, Sinnescentrum, Neurokirurgiska kliniken US.
Vise andre og tillknytning
2012 (engelsk)Inngår i: Journal of Neuroscience Methods, ISSN 0165-0270, E-ISSN 1872-678X, Vol. 207, nr 1, s. 17-22Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an efficacious treatment in patients with advanced Parkinson's disease, yet the mechanisms of STN DBS are poorly understood. The aims of this study were to develop a useful method for studying neurotransmitter alterations during DBS and for the pharmacokinetics of L-dopa in brain tissue. Ten patients with Parkinson's disease participated, whereof two had no previous L-dopa medication. The electrodes and catheters were placed using MRI-guided stereotaxic targeting. Two microdialysis probes were placed, one in the right internal globus pallidus, and one in a brachial vein. The quadripolar deep brain electrodes were placed in the right STN. Microdialysates from brain tissue and blood were collected in 15-min fractions at baseline and during DBS. After stimulation new baseline fractions were taken and finally three fractions during continuous intravenous infusion of L-dopa. Clinical evaluation showed that both DBS and L-dopa infusion gave good relief of rigidity and tremor in all ten patients. During DBS the L-dopa levels in the brain increased in some of the patients but did not persist during the whole stimulation period. The concentration in brain increased substantially during intravenous L-dopa infusion. A number of catecholamines and their metabolites were analysed with high pressure liquid chromatography (HPLC). With our study we could show that this model is suitable for the monitoring of neurotransmitters and for pharmacokinetic studies in human brain, although we found that the sampling time was too short to follow the possible alterations in brain activity caused by DBS.

sted, utgiver, år, opplag, sider
Elsevier, 2012. Vol. 207, nr 1, s. 17-22
Emneord [en]
Parkinson's disease; Microdialysis; L-dopa; Pharmacokinetics; Stereotaxy; Neurotransmitter
HSV kategori
Identifikatorer
URN: urn:nbn:se:liu:diva-89705DOI: 10.1016/j.jneumeth.2012.02.021OAI: oai:DiVA.org:liu-89705DiVA, id: diva2:609106
Tilgjengelig fra: 2013-03-04 Laget: 2013-03-04 Sist oppdatert: 2018-01-12
Inngår i avhandling
1. Biochemical and pharmacokinetic studies in vivo in Parkinson’s disease
Åpne denne publikasjonen i ny fane eller vindu >>Biochemical and pharmacokinetic studies in vivo in Parkinson’s disease
2013 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Parkinson’s disease (PD) is a neurodegenerative disease affecting approximately 25000 people in Sweden. The main cause of the disease is the degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNc) projecting to the striatum. The motor symptoms of PD, due to decreased levels of dopamine, includes bradykinesia, rigidity and tremor.

During the 1960ies oral L-dopa treatment was introduced increasing quality of life for PD patients. In recent decades, enzyme inhibitors have been introduced, increasing bioavailability of L-dopa in plasma. After 5-10 years of L-dopa treatment, 50% of PD patients develop disabling dyskinesias. This can be due to rapid changes in L-dopa conentrations with non physiological stimulation of the dopamine receptor.

For over 20 years deep brain stimulation (DBS) has grown to be a good neurosurgical procedure for improving quality of life in advanced PD with disabling dyskinesias. With stereotactic technique, electrodes are implanted in the brain and connected to a pacemaker sending electrical impulses. The most common target in PD is the subthalamic nucleus (STN). The knowledge about DBS mechanism(s) and its interaction with L-dopa is unsatisfactory.

The aims of this thesis were; to study the effect of the enzyme inhibitor entacapone on the L-dopa concentration over the blood brain barrier (BBB); to study possible interactions between L-dopa and DBS; to study alterations in neurotransmitters during DBS; to visualize microdialysis catheters in anatomical targets and to estimate sampling area of the catheters.

In all four papers the microdialysis technique was used. It is a well-established technique for continuous sampling of small water-soluble molecules within the extracellular fluid space in vivo, allowing studies of pharmaceutical drugs and neurotransmitters.

We showed that entacapone increases the bioavailability of L-dopa in blood with a subsequent increase of L-dopa peak levels in the cerebrospinal fluid. This in turn may cause a larger burden on the dopaminergic neurons causing an increased degeneration rate and worsening of the dyskinesias; we showed that 18% of L-dopa crosses the BBB and that there is a possible interaction between L-dopa and DBS, L-dopa concentrations increase during concomitant STN DBS, which can clarify why its possible to decrease L-dopa medication after DBS surgery. The research has also shown that STN DBS has an effect on various neurotransmitter systems, mainly L-dopa, dopamine and GABA. We showed that STN DBS may have an effect on the SNc, resulting in putaminal dopamine release.

We have shown that with stereotactic technique, it is safe to do microdialysis sampling in specific areas in the human brain. Simulations with the finite element method combined with patient specific preoperative MRI and postoperative CT images gave us exact knowledge about the positions of the catheters and that the studied structures were the intended. The research has given an assumption of the maximum tissue volume that can be sampled around the microdialysis catheters.

sted, utgiver, år, opplag, sider
Linköping: Linköping University Electronic Press, 2013. s. 78
Serie
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1345
HSV kategori
Identifikatorer
urn:nbn:se:liu:diva-91294 (URN)978-91-7519-737-1 (ISBN)
Disputas
2013-05-17, Berzeliussalen, Hälsouniversitetet, Campusu US, Linköpings universitet, Linköping, 09:00 (svensk)
Opponent
Veileder
Tilgjengelig fra: 2013-04-19 Laget: 2013-04-19 Sist oppdatert: 2018-01-12bibliografisk kontrollert

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