Parkinson's disease pathophysiology: Difference between revisions
Jump to navigation
Jump to search
No edit summary |
No edit summary |
||
| Line 8: | Line 8: | ||
==Pathophysiology== | ==Pathophysiology== | ||
The underlying [[pathophysiology]] of [[Parkinson's disease|Parkinson disease]] is [[dopamine]] depletion.The [[substantia nigra]] ([[Substantia nigra|SN]]), [[striatum]] ([[Caudate nucleus|caudate]] and [[putamen]]), [[globus pallidus]] ([[Globus pallidus|GP]]), [[subthalamic nucleus]] ([[Subthalamic nucleus|STN]]) and [[thalamus]] contribute with each other to make the [[extrapyramidal system]] or [[basal ganglia]]. The impulses from [[hippocampus]], [[amygdala]] and prefrontal supplementary motor area to the [[basal ganglia]] are [[Excitatory synapse|excitatory]] mediated by [[glutamate]]. The major [[dopaminergic]] [[neurons]] are in [[substantia nigra]] and are responsible for [[dopaminergic]] input of [[striatum]]. The striatal output is [[Inhibitory synapses|inhibitory]] ([[GABA]]) despite the [[Excitatory synapse|excitatory]] ([[glutamate]]) output of [[Subthalamic nucleus|STN]] to the [[globus pallidus]] (medial and lateral). There are 5 [[dopamine receptors]] (D1_D5) which are in [[basal ganglia]] and [[limbic system]]. [[D1 receptor|D1]] and [[D2 receptor|D2]] are mostly found in the dorsal [[striatum]] (motor) and are activated through [[dopaminergic]] pathway from [[Substantia nigra|SNc]], as a result, they are very important in the [[pathophysiology]] of Parkinson disease. D3 and D4 are located mostly in [[Mesolimbic system|mesolimbic]] or emotional part of the [[brain]] and D5 in [[hippocampus]]/[[hypothalamus]] area.<ref name="pmid11052222">{{cite journal |vauthors=Gerfen CR |title=Molecular effects of dopamine on striatal-projection pathways |journal=Trends Neurosci. |volume=23 |issue=10 Suppl |pages=S64–70 |date=October 2000 |pmid=11052222 |doi= |url=}}</ref> In the course of the disease [[dopamine]] depletion of [[nigrostriatal pathway]] will lead to denervation hypersensitivity and increasing number of [[D2 receptor|D2]] receptors in dorsal [[putamen]].<ref name="pmid15509741">{{cite journal |vauthors=Bamford NS, Robinson S, Palmiter RD, Joyce JA, Moore C, Meshul CK |title=Dopamine modulates release from corticostriatal terminals |journal=J. Neurosci. |volume=24 |issue=43 |pages=9541–52 |date=October 2004 |pmid=15509741 |doi=10.1523/JNEUROSCI.2891-04.2004 |url=}}</ref> There are two pathways in this system: Direct and indirect pathway. In the indirect pathway starts with [[inhibition]] of [[striatum]] via [[D2 receptor]] which in turn [[Inhibition|inhibits]] [[neurons]] of lateral [[Globus pallidus|GP]] by [[GABA]] which [[Inhibition|inhibits]] the inhibition of [[Subthalamic nucleus|STN]] by lateral [[Globus pallidus|GP]]. [[Subthalamic nucleus|STN]] provides [[Excitatory synapse|excitatory]] action on [[Globus pallidus|GP]] internal and [[Substantia nigra|SNr]] via [[glutamate]]. [[Globus pallidus|GPi]] inhibit [[thalamus]] by [[GABA]] but [[cortex]] input from [[thalamus]] is [[Excitatory synapse|excitatory]]. Direct pathway starts with [[excitation]] of [[striatum]] by stimulation of [[D1 receptor|D1 receptors]], then [[striatum]] inhibits [[Globus pallidus|GP]] internal and [[Substantia nigra|SNr]] by [[GABA]] directly. Reduced number of [[dopaminergic]] [[neurons]] lead to increased inhibition of [[thalamus]] and as a result, decrease excitation of [[Cortex|brain cortex]], causing [[bradykinesia]].<ref name="pmid16830313">{{cite journal |vauthors=Gatev P, Darbin O, Wichmann T |title=Oscillations in the basal ganglia under normal conditions and in movement disorders |journal=Mov. Disord. |volume=21 |issue=10 |pages=1566–77 |date=October 2006 |pmid=16830313 |doi=10.1002/mds.21033 |url=}}</ref> Our [[brain]] has some compensatory mechanism fighting [[dopamine]] depletion. It can increase the synthesis of [[dopamine]], [[gap junctions]] and the number of [[D2 receptor|D2 receptors]]. It can also reduce the uptake of dopamine from synaptic space. | The underlying [[pathophysiology]] of [[Parkinson's disease|Parkinson disease]] is [[dopamine]] depletion.The [[substantia nigra]] ([[Substantia nigra|SN]]), [[striatum]] ([[Caudate nucleus|caudate]] and [[putamen]]), [[globus pallidus]] ([[Globus pallidus|GP]]), [[subthalamic nucleus]] ([[Subthalamic nucleus|STN]]) and [[thalamus]] contribute with each other to make the [[extrapyramidal system]] or [[basal ganglia]]. The impulses from [[hippocampus]], [[amygdala]] and prefrontal supplementary motor area to the [[basal ganglia]] are [[Excitatory synapse|excitatory]] mediated by [[glutamate]]. The major [[dopaminergic]] [[neurons]] are in [[substantia nigra]] and are responsible for [[dopaminergic]] input of [[striatum]]. The striatal output is [[Inhibitory synapses|inhibitory]] ([[GABA]]) despite the [[Excitatory synapse|excitatory]] ([[glutamate]]) output of [[Subthalamic nucleus|STN]] to the [[globus pallidus]] (medial and lateral). There are 5 [[dopamine receptors]] (D1_D5) which are in [[basal ganglia]] and [[limbic system]]. [[D1 receptor|D1]] and [[D2 receptor|D2]] are mostly found in the dorsal [[striatum]] (motor) and are activated through [[dopaminergic]] pathway from [[Substantia nigra|SNc]], as a result, they are very important in the [[pathophysiology]] of Parkinson disease. D3 and D4 are located mostly in [[Mesolimbic system|mesolimbic]] or emotional part of the [[brain]] and D5 in [[hippocampus]]/[[hypothalamus]] area.<ref name="pmid11052222">{{cite journal |vauthors=Gerfen CR |title=Molecular effects of dopamine on striatal-projection pathways |journal=Trends Neurosci. |volume=23 |issue=10 Suppl |pages=S64–70 |date=October 2000 |pmid=11052222 |doi= |url=}}</ref> In the course of the disease [[dopamine]] depletion of [[nigrostriatal pathway]] will lead to denervation hypersensitivity and increasing number of [[D2 receptor|D2]] receptors in dorsal [[putamen]].<ref name="pmid15509741">{{cite journal |vauthors=Bamford NS, Robinson S, Palmiter RD, Joyce JA, Moore C, Meshul CK |title=Dopamine modulates release from corticostriatal terminals |journal=J. Neurosci. |volume=24 |issue=43 |pages=9541–52 |date=October 2004 |pmid=15509741 |doi=10.1523/JNEUROSCI.2891-04.2004 |url=}}</ref> There are two pathways in this system: Direct and indirect pathway. In the indirect pathway starts with [[inhibition]] of [[striatum]] via [[D2 receptor]] which in turn [[Inhibition|inhibits]] [[neurons]] of lateral [[Globus pallidus|GP]] by [[GABA]] which [[Inhibition|inhibits]] the inhibition of [[Subthalamic nucleus|STN]] by lateral [[Globus pallidus|GP]]. [[Subthalamic nucleus|STN]] provides [[Excitatory synapse|excitatory]] action on [[Globus pallidus|GP]] internal and [[Substantia nigra|SNr]] via [[glutamate]]. [[Globus pallidus|GPi]] inhibit [[thalamus]] by [[GABA]] but [[cortex]] input from [[thalamus]] is [[Excitatory synapse|excitatory]]. Direct pathway starts with [[excitation]] of [[striatum]] by stimulation of [[D1 receptor|D1 receptors]], then [[striatum]] inhibits [[Globus pallidus|GP]] internal and [[Substantia nigra|SNr]] by [[GABA]] directly. Reduced number of [[dopaminergic]] [[neurons]] lead to increased inhibition of [[thalamus]] and as a result, decrease excitation of [[Cortex|brain cortex]], causing [[bradykinesia]].<ref name="pmid16830313">{{cite journal |vauthors=Gatev P, Darbin O, Wichmann T |title=Oscillations in the basal ganglia under normal conditions and in movement disorders |journal=Mov. Disord. |volume=21 |issue=10 |pages=1566–77 |date=October 2006 |pmid=16830313 |doi=10.1002/mds.21033 |url=}}</ref> Our [[brain]] has some compensatory mechanism fighting [[dopamine]] depletion. It can increase the synthesis of [[dopamine]], [[gap junctions]] and the number of [[D2 receptor|D2 receptors]].<ref name="pmid11052221">{{cite journal |vauthors=Calabresi P, Centonze D, Bernardi G |title=Electrophysiology of dopamine in normal and denervated striatal neurons |journal=Trends Neurosci. |volume=23 |issue=10 Suppl |pages=S57–63 |date=October 2000 |pmid=11052221 |doi= |url=}}</ref><ref name="pmid12464455">{{cite journal |vauthors=Moore H, Grace AA |title=A role for electrotonic coupling in the striatum in the expression of dopamine receptor-mediated stereotypies |journal=Neuropsychopharmacology |volume=27 |issue=6 |pages=980–92 |date=December 2002 |pmid=12464455 |doi=10.1016/S0893-133X(02)00383-4 |url=}}</ref> It can also reduce the uptake of dopamine from synaptic space.<ref name="pmid16081470">{{cite journal |vauthors=Adams JR, van Netten H, Schulzer M, Mak E, Mckenzie J, Strongosky A, Sossi V, Ruth TJ, Lee CS, Farrer M, Gasser T, Uitti RJ, Calne DB, Wszolek ZK, Stoessl AJ |title=PET in LRRK2 mutations: comparison to sporadic Parkinson's disease and evidence for presymptomatic compensation |journal=Brain |volume=128 |issue=Pt 12 |pages=2777–85 |date=December 2005 |pmid=16081470 |doi=10.1093/brain/awh607 |url=}}</ref> | ||
Revision as of 08:53, 31 March 2018
|
Parkinson's disease Microchapters |
|
Diagnosis |
|---|
|
Treatment |
|
Case Studies |
|
Parkinson's disease pathophysiology On the Web |
|
American Roentgen Ray Society Images of Parkinson's disease pathophysiology |
|
Risk calculators and risk factors for Parkinson's disease pathophysiology |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Pathophysiology
The underlying pathophysiology of Parkinson disease is dopamine depletion.The substantia nigra (SN), striatum (caudate and putamen), globus pallidus (GP), subthalamic nucleus (STN) and thalamus contribute with each other to make the extrapyramidal system or basal ganglia. The impulses from hippocampus, amygdala and prefrontal supplementary motor area to the basal ganglia are excitatory mediated by glutamate. The major dopaminergic neurons are in substantia nigra and are responsible for dopaminergic input of striatum. The striatal output is inhibitory (GABA) despite the excitatory (glutamate) output of STN to the globus pallidus (medial and lateral). There are 5 dopamine receptors (D1_D5) which are in basal ganglia and limbic system. D1 and D2 are mostly found in the dorsal striatum (motor) and are activated through dopaminergic pathway from SNc, as a result, they are very important in the pathophysiology of Parkinson disease. D3 and D4 are located mostly in mesolimbic or emotional part of the brain and D5 in hippocampus/hypothalamus area.[1] In the course of the disease dopamine depletion of nigrostriatal pathway will lead to denervation hypersensitivity and increasing number of D2 receptors in dorsal putamen.[2] There are two pathways in this system: Direct and indirect pathway. In the indirect pathway starts with inhibition of striatum via D2 receptor which in turn inhibits neurons of lateral GP by GABA which inhibits the inhibition of STN by lateral GP. STN provides excitatory action on GP internal and SNr via glutamate. GPi inhibit thalamus by GABA but cortex input from thalamus is excitatory. Direct pathway starts with excitation of striatum by stimulation of D1 receptors, then striatum inhibits GP internal and SNr by GABA directly. Reduced number of dopaminergic neurons lead to increased inhibition of thalamus and as a result, decrease excitation of brain cortex, causing bradykinesia.[3] Our brain has some compensatory mechanism fighting dopamine depletion. It can increase the synthesis of dopamine, gap junctions and the number of D2 receptors.[4][5] It can also reduce the uptake of dopamine from synaptic space.[6]
References
- ↑ Gerfen CR (October 2000). "Molecular effects of dopamine on striatal-projection pathways". Trends Neurosci. 23 (10 Suppl): S64–70. PMID 11052222.
- ↑ Bamford NS, Robinson S, Palmiter RD, Joyce JA, Moore C, Meshul CK (October 2004). "Dopamine modulates release from corticostriatal terminals". J. Neurosci. 24 (43): 9541–52. doi:10.1523/JNEUROSCI.2891-04.2004. PMID 15509741.
- ↑ Gatev P, Darbin O, Wichmann T (October 2006). "Oscillations in the basal ganglia under normal conditions and in movement disorders". Mov. Disord. 21 (10): 1566–77. doi:10.1002/mds.21033. PMID 16830313.
- ↑ Calabresi P, Centonze D, Bernardi G (October 2000). "Electrophysiology of dopamine in normal and denervated striatal neurons". Trends Neurosci. 23 (10 Suppl): S57–63. PMID 11052221.
- ↑ Moore H, Grace AA (December 2002). "A role for electrotonic coupling in the striatum in the expression of dopamine receptor-mediated stereotypies". Neuropsychopharmacology. 27 (6): 980–92. doi:10.1016/S0893-133X(02)00383-4. PMID 12464455.
- ↑ Adams JR, van Netten H, Schulzer M, Mak E, Mckenzie J, Strongosky A, Sossi V, Ruth TJ, Lee CS, Farrer M, Gasser T, Uitti RJ, Calne DB, Wszolek ZK, Stoessl AJ (December 2005). "PET in LRRK2 mutations: comparison to sporadic Parkinson's disease and evidence for presymptomatic compensation". Brain. 128 (Pt 12): 2777–85. doi:10.1093/brain/awh607. PMID 16081470.