A Parkinson's Glossary

A language guide for the science of Parkinson’s

When first diagnosed with PD, there is so much to get used to and understand – not least the language of neurology. As ever, the better informed you are the more you will gain from consultations with neurologists and conversations with researchers. The concise glossary below will, we hope, provide better understanding for those new to the subject.

ACETYLCHOLINE: A neurotransmitter that is also involved in controlling smooth movement in the brain. Loss of dopamine causes the rigidity seen in Parkinson’s patients due to decrease in basal ganglia control.

AGONISTS: A chemical that can combine with a receptor on a cell to produce a physiological reaction.

AKINESIA: Inability to move spontaneously

ALPHA SYNUCLEIN (SNCA): A protein postulated to play a central role in the pathogenesis of Parkinson.s disease, Alzheimer.s disease, and other neurodegenerative disorders.

AMANTADINE: Can be used as a single therapy or with L-DOPA to decrease the L-DOPA created motor fluctuations and L-DOPA related dyskinesis. Can also be used as an antiviral.

AMYGDALA: Located deep in the medial temperal lobe in complex mammals. Involved in fear, anxiety in particular in the formation of memories involved in emotion.

ANTICHOLINERGICS: Helps to restrict the action of acetylcholine by blocking binding at the receptor. Examples of such are below:

  • benztropine mesylate,
  • biperiden hydrochloride,
  • orphenadrine citrate,
  • procyclidine hydrochloride,
  • trihexyphenidyl hydrochloride.
ANTAGONISTS: Any compound that decreases the binding of an agonist to a receptor, by either blocking the activation site or changing the conformation of the receptor. ATAXIA: Inability to coordinate voluntary muscle movements; unsteady movements and staggering gait.

ATP13A2 (PARK 9): A gene which may be involved in early onset Parkinson’s. Codes for an enzyme; ATPase 13A2.

AUTONOMIC NERVOUS SYSTEM (ANS): Consisting of sympathetic and parasympathetic aspects and controls involuntary actions, in particular the heart, smooth muscle and glands.

AUTOSOMAL: When referring to chromosomes all the chromosomes that are non sex related chromosomes are autosomal.

AUTOSOMAL RECESSIVE: Suggests that in order for a particular trait to be expressed both parents have to have the particular allele or gene, therefore the presence of another allele will not allow this allele to be expressed. In the case of Parkinson’s the Parkin gene is autosomal recessive.

AXON: Nerve fibers that carry electrical impulses through the brain and spinal cord; they are surrounded by a protective sheath called myelin; in multiple sclerosis the axon can be damaged.

BASAL GANGLIA: Clusters of neurons, which include the caudate nucleus, putamen, globus pallidus and substantia nigra, that are located deep in the brain and play an important role in movement. Cell death in the substantia nigra contributes to Parkinsonian signs.

BENSERAZIDE AS CO BENELDOPA (BAN), brand names- Madopar (UK): Catalyses L-DOPA to dopamine 5-HTTP to serotonin and tryptophan to tryptamine. Therefore in Parkinson’s patients speeds up break down of L-DOPA.

BLOOD BRAIN BARRIER: The separating membrane between the cerebrospinal fluid (CSF) and the blood a tight physical barrier that keeps immune cells out of the brain, normally.

BRADYKINESIA: Decrease in motor activity. It is associated with basal ganglia diseases, mental disorders and prolonged inactivity due to illness.

BRAIN STEM: The part of the brain continuous with the spinal cord and comprising the medulla oblongata, pons, midbrain and parts of the hypothalamus. Damage to this area may cause non-motor dysfunctions such as sleep disorders and autonomic dysfunction.

CALCIUM: Calcium is important for signalling and is involved in energy formation in mitochondria. Calcium overload in substantia nigra kills cells.

CARBIDOPA: A drug given with levodopa to decrease its metabolism via inhibition of Dopa decarboxylase.

CAUDATE NUCLEUS: Located in the basal ganglia important in learning and memory.

CEREBELLUM: Part of the hind brain controls learnt actions such as riding a bike, actions that feel second nature.

CEREBROSPINAL FLUID (CSF): A water cushion surrounding the brain and spinal cord protecting them from physical impact.

CHRONIC: Describing a disease of long duration involving very slow changes. Such disease is often of gradual onset. The term does not imply anything about the severity of a disease.

COMPUTED TOMOGRAPHY (CT): Is a medical imaging method employing tomography created by computer processing. Digital geometry processing is used to generate a three-dimensional image of the inside of an object from a large series of two-dimensional X-ray images taken around a single axis of rotation.

COMT (catechol-O-methyltransferase): Is an enzyme that breaks down dopamine, adrenaline and noradrenaline.

CYTOKINES: Are any of a number of small proteins that are secreted by specific cells of the immune system and that carry signals locally between cells, and thus have an effect on other cells. Higher levels of proinflammatory cytokines are found in Parkinson’s brains. Unlike growth factors they have no specific role in cell proliferation are and are primarily linked to blood and immune cells. They have also been known to be involved in apoptosis.

DEEP BRAIN STIMULATION (DBS): Involves the implantation of a medical device that acts as a brain pacemaker sending electrical impulses to specific areas. In Parkinson’s patients the device is attached to either the subthalamic nucleus or the globus pallidus.

DEMENTIA: A decline in cognitive function due to damage or disease in the brain beyond what might be expected from normal aging. Areas particularly affected include memory, attention, judgement, language and problem solving.

DENDRITE: (From Greek δένδρον déndron, “tree”) are the branched projections of a neuron that act to conduct the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project.

DEPRESSION: A state of low mood. Some consider it a dysfunction, while others see it as an adaptive defense mechanism.

DJ-1: Mutations in this gene have been proved to cause an autosomal recessive form of Parkinson’s disease in this gene. It may also have an affect in the idiopathic form of the disease. The function of the protein created by DJ-1 is unknown still.

DOPA DECARBOXYLASE INHIBITORS: Such as carbidopa, act to decrease the breakdown of levodopa in the body allowing more to reach the brain where it is converted to dopamine. Particularly useful for Parkinson’s patients when used alongside levodopa.

DOPAMINE: Acts as one of the brain’s messengers to signal movement and maintain balance and coordination

DOPAMINE AGONISTS: Such as; bromocriptine mesylate (Parlodel), pergolide, pramipexole (Mirapex), ropinirole hydrochloride (Requip), piribedil, cabergoline, apomorphine (Apokyn) and lisuride. Act as dopamine, but is not actually dopamine. These are used in the early stages of Parkinson’s disease or in the late stages when levodopa is no longer as effective.

DOPAMINERGIC PATHWAYS: Split into four major groups the nigrostriatal, mesocortical, mesolimbic and tuberoinfundibular.

  • Nigrostriatal- Connects the substantia nigra to the striatum. Involved heavily in Parkinson’s.
  • Mesocortical and mesolimbic from Ventral Tegmental Area to Nucleus Accumbens, Amygdala & Hippocampus and Prefrontal Cortex. Involved in memory, motivation, emotional response, reward and addiction. Can cause hallucinations and schizophrenia if not functioning properly
  • Tuberoinfundibular- from hypothalamus to pituitary gland involved in hormonal regulation, maternal behavior (nurturing), pregnancy and sensory processes

DYSARTHRIA: Impaired speech function.

DYSKINESIA: Abnormality in performing voluntary muscle movements

DYSPHAGIA: Difficulty in swallowing.

EMBRYONIC STEM (ES) CELLS: see stem cells
ENTACAPONE: A Parkinson’s drug that is used alongside levodopa and carbidopa. Inhibits COMT decreasing breakdown of levodopa, dopamine, adrenaline and noradrenaline.

FUNCTIONAL MAGNETIC RESONANCE IMAGING (fMRi): An imaging technique designed specifically for the brain. It measures rate at which oxygen is removed from the blood to the cells, . Therefore suggesting the activity of a particular area of the brain.
GABA: (Gamma amino butyric acid) the principal inhibitory neurotransmitter in human brain. GABA neurons project from the striatum to the substantia nigra and are involved in motor control.

GDNF: see growth factors

GENE THERAPY: Gene therapy is the insertion of genes into an individual’s cells and tissues to treat hereditary diseases where deleterious mutant alleles can be replaced with functional ones..

GENOTYPE: The collection of genetic material in an organism that gives rise to its characteristics.

GLIA: Glial cells, commonly called neuroglia or simply glia (Greek for “glue”), are non-neuronal cells that maintain homeostasis, form myelin, and provide support and protection for the brain’s neurons.

GLOBUS PALLIDUS: A major part of the basal ganglia involved in movement control. Split into two main parts the internal globus pallidus (GPi), the external globus pallidus (GPe). Deep brain stimualtion of the GPi is shown to have an increase in motor function in PD patients.

GLUTAMATE: The main excitatory neurotransmitter in the human brain. A major projection from the cerebral cortex to the striatum modulates motor activity

GROWTH FACTORS: Useful for regulating a number of cell processes, in particular cell growth, proliferation and differentiation. Some growth factors are being looked at to try to promote the survival of the neural cells that are degenerating in PD.

  • Glial cell line dervied nerve growth factor (GDNF): has showed positive results in regards to cell proliferation and has been shown to reduce the tremors caused by levodopa.
  • Fibroblast growth factor (FGF): Possible genetic link to Parkinson’s disease on the FGF20 gene found in Japanese people.
  • Vascular endothelial growth factor-B (VEGF-B): Has been shown to have neuroprotective affects in Parkinson’s disease and is released in neurodegenerative challenges to the brain.
HIPPOCAMPUS: A complex neural structure (shaped like a sea horse) located on the floor of each lateral ventricle; intimately involved in motivation and emotion as part of the limbic system; has a central role in the formation of memories.

HYPERKINESIA: Abnormal increase in movement and/or muscle activity.

HYPOKINESIA: Abnormal decrease in movement and/or muscle activity.

HYPOTHALAMIC PITUITARY ADRENAL AXIS (HPA): Made up of the hypothalamus, pituitary gland and the adrenal cortex, these three components are the primary components of the endocrine system and have a wide range of functions from stimulating the stress response to control of digestion, the immune system, mood, sexuality and energy storage and consumption.

HYPOTHALAMUS: Located at the bottom of the brain and links the limbic system to the pituitary gland.

IDIOPATHIC: Arising from an unknown cause.
LEUCINE RICH REPEAT KINASE 2 (LRRK2): Created by LRRK2 gene which when mutated can lead to Parkinson’s. Four different LRRK2 gene variants are found in Parkinson’s patients compared to just one in the general population.

LEVODOPA: A precursor to dopamine that can pass through the blood brain barrier and then be converted into dopamine the neurotransmitter that is lacking in Parkinson’s disease.

LEWY BODIES: Abnormal aggregates of proteins found in both Parkinson’s and Alzheimer’s disease.
MAO (MONOAMINE OXIDASE): Two subtypes, MAO-A and MAO-B, catalyse the breakdown of amines so replacing the amine group with an oxygen molecule.

MAO A INHIBITORS: Inhibitor of the MAO A enzyme which is responsible for the metabolism of dietary tyramine. MAO-A inhibitors can cause tyramine-induced hypertension.

MAO B INHIBITORS: e.g. selegiline, rasagiline. Inhibit the break down of dopamine via monoamine oxidase B, better for treatment of PD than the normal non-selective MAO inhibitors as less adverse effects from tyramine-induced hypertension.

N-METHYL-4-PHENYL-1,2,3,6-TETRAHYDROPYRIDINE (MPTP): A neurotoxin created after by failed effort to synthesize a recreational drug. It causes irreversible Parkinson’s disease after conversion to MPP+ by MAO B. The MPTP acts by killing the dopaminergic neurons in the substantia nigra.

MICROGLIA: The first immune defence mechanism in the brain and central nervous system.

MOTOR SKILLS: The degree of control or coordination given to the skeletal muscles.

MAGNETIC RESONANCE IMAGING (MRI): Is primarily a noninvasive medical imaging technique used in radiology to visualize detailed internal structure and limited function of the body. MRI provides much greater contrast between the different soft tissues of the body than computed tomography (CT) does, making it especially useful in neurological (brain), musculoskeletal, cardiovascular, and oncological (cancer) imaging.

MULTIPLE SYSTEM ATROPHY (MSA): Is a degenerative neurological disorder related to Parkinson’s but more severe, with problems of movement, balance and autonomic function.

NEUROMELANIN: Formed as a byproduct of dopamine it is believed to bind heavily with iron. Gives the substantia nigra its black appearance.

NEUROMODULATOR: A substance other than a neurotransmitter, released by a neuron at a synapse and either enhancing or dampening their activities.

NEUROPROTECTION: The term neuroprotection refers to mechanisms within the nervous system which protect neurons from apoptosis or degeneration, for example following a brain injury or as a result of chronic neurodegenerative diseases.

NEUROTRANSMITTER: A chemical messenger in the nervous system that permits communication between two neuronal cells, normally across a synapse. Examples include; dopamine, acetylcholine, adrenaline, noradrenaline, serotonin, glutamate, GABA, etc.

NICOTINE: Acts as an agonist at nicotinic receptors. Nicotine is thought to decrease chances of developing Parkinson’s disease.

PARADOXICAL KINESIS: The movement of a person who previously could not, usually in response to an extreme stress stimulus, cases of this are reported in Parkinson’s disease.

PARKIN: Parkin is a protein which in humans is encoded by the PARK2 gene. The precise function of this protein is unknown; however, parkin is also the gene involved in the creation of the Parkin protein, and is the causative gene for autosomal recessive Parkinson’s disease.

PARKINSONISM: A group of neurological diseases whose main features include slowness and paucity of spontaneous movement (bradykinesia), tremors and rigidity of the muscles.

PARKINSONIAN GAIT: A type of stooped, shuffling movement that is common in Parkinson’s.

PINK-1: A gene that encodes serine/threonine kinase, an enzyme found in mitochondria that stops stress related cell destruction. PINK-1 mutations have an involvement in early onset Parkinson’s disease. Lack of PINK-1 causes an overload of calcium in mitochondria and indirectly cell death. The substantia nigra is shown to be particularly sensitive to PINK-1 mutations.

POSITRON EMISSION TOMOGRAPHY (PET): A medical imaging technique which detects the gamma rays produced by positrons emitted from injected radionuclides, such as radioactive glucose.

PwP: People with Parkinson’s.

REACTIVE OXYGEN SPECIES (ROS): Chemically-reactive molecules containing oxygen that may trigger cell death. Examples include oxygen ions and peroxides.
RECEPTOR: A protein structure, embedded in either the plasma membrane or the cytoplasm of a cell, to which specific kinds of signaling molecules may attach.
SHUFFLE GAIT: Short, uncertain steps, with minimal flexion and toes dragging. Often present in Parkinson’s.

SODIUM CHANNEL: Voltage gated channels in nerve cell membranes that allow the generation of action potentials. Sodium channels may be a target for new drugs in Parkinson’s.

SPECT: Single photon emission computed tomography is a nuclear medicine tomographic imaging technique using gamma rays and able to provide 3D information for instance on brain chemistry.

STEM CELLS: Found in all multicellular organisms and are characterized by their ability to differentiate into a diverse range of specialized cell types. Stem cells are a potential line of treatment in Parkinson’s, either directly replacing the old nigrostriatal neuronal cells or creating growth factor releasing cells. Problems have arisen due to the inability to stop growth which may cause tumour growth.

STRIATUM: Part of the basal ganglia, it is a large cluster of nerve cells, consisting of the caudate nucleus and the putamen, that controls movement, balance, and walking; the neurons of the striatum require dopamine to function.

SUBSTANTIA NIGRA: Latin for black substance. Is a brain structure located in the midbrain that plays an important role in reward, addiction, and movement. Parts of the substantia nigra appear darker than neighboring areas due to high levels of melanin in dopaminergic neurons. The substantia nigra is part of the basal ganglia; the other parts of the basal ganglia include the striatum (caudate nucleus, putamen, and nucleus accumbens), globus pallidus, and subthalamic nucleus. Made up of the pars compacta and the pars reticulata.

  • Pars compacta: Primarily involved in Parkinson’s, are mainly dopaminergic and black due to the high concentration of melatonin.
  • Pars reticulata: Mainly GABAergic neurons.

SUBTHALAMIC NUCLEUS (STN): The subthalamic nucleus is a small lens-shaped nucleus involved in movement control. As suggested by its name, the subthalamic nucleus is located ventral to the thalamus. It is also dorsal to the substantia nigra and medial to the internal capsule.

SYNAPSE: The junction between two neurons (axon to dendrite) or between a neuron and a muscle; nerve impulses cross a synapse through the action of neurotransmitters.

SYNAPTIC PLASTICITY: The ability of the connection, or synapse, between two neurons to change in strength.

TAU PROTEINS: Proteins that stabilize microtubules. They are abundant in neurons in the central nervous system and are less common elsewhere. When tau proteins are defective, and no longer stabilize microtubules properly, they can result in dementias, such as Alzheimer’s disease.

TAYOPATHIES: A class of neurodegenerative diseases resulting from the pathological aggregation of tau protein in so-called neurofibrillary tangles (NFT) in the human brain.

THALAMUS: A midline paired symmetrical structure situated between the cerebral cortex and midbrain, both in terms of location and neurological connections.

T.R.A.P.: Acronym for four primary PD symptoms:

  • Tremor: Shaking of limb (usually hand) while at rest
  • Rigidity: Muscle stiffness and resistance to movement
  • Akinesia/bradykinesia: see above
  • Postural instability: See ataxia
TRANSCRIPTION FACTORS: Proteins in eukaryotes that regulate the transcription of other genes

TRANSLATION: The process of ribosomal reading of mRNA molecules in the cytoplasm and attaching correct amino acids at the right points to allow the formation of a protein molecule

TYRAMINE-INDUCED HYPERTENSION: Due to an increase in tyramine in the blood which forces noradrenaline out of vesicles and into circulation causing high blood pressure.

UBIQUITIN: Involved in the degradation of certain proteins, it sticks to proteins that need to be degraded and the process of ubiquitination later breaks down the protein with various enzymes. In Parkinson’s disease excess proteins form causing the eventual death of the cell.
VESICLE: A organelle in a cell that seperates other molecules from the rest of the cell. They can transport neurotransmitters to the cell surface and release them to stimulate other cells. This occurs in synaptic transmission.

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