Purkinje cell

Purkinje cells or Purkinje neurons, named for Czech physiologist Jan Evangelista Purkyně who identified them in 1837,^{[citation needed]} are a unique type of prominent large neurons located in the cerebellar cortex of the brain. With their flask-shaped cell bodies, many branching dendrites, and a single long axon, these cells are essential for controlling motor activity. Purkinje cells mainly release GABA (gamma-aminobutyric acid) neurotransmitter, which inhibits some neurons to reduce nerve impulse transmission. Purkinje cells efficiently control and coordinate the body's motor motions through these inhibitory actions.^[2][3]

Structure

These

Canonically, each adult Purkinje cell receives approximately 500 climbing fiber synapses, all originating from a single climbing fiber from the inferior olive.^[6] This has led to the notion that a "highly conserved one-to-one relationship renders Purkinje dendrites into a single computational compartment".^[7] However, multi-innervation has now been found that "occurs" in mice among the subset of Purkinje cells with multiple primary dendrites, a dendritic motif that is uncommon in rodents but "predominant" in humans.^[7]

Both basket and stellate cells (found in the cerebellar

Purkinje cells send inhibitory projections to the deep cerebellar nuclei, and constitute the sole output of all motor coordination in the cerebellar cortex.

Molecular

The

Mammalian embryonic research has detailed the neurogenic origins of Purkinje cells.[14] During early development Purkinje cells arise in the ventricular zone in the neural tube, the nervous system´s precursor in the embryo. All cerebellar neurons derive from germinal neuroepithelia from the ventricular zone.^[15] Purkinje cells are specifically generated from progenitors in the ventricular neuroepithelium of the embryonic cerebellar primordium.^[16] The first cells generated from the cerebellar primordium form a cap over a diamond-shaped cavity of the developing brain called the fourth ventricle forming the two cerebellar hemispheres. The Purkinje cells that develop later are those of the cerebellum's center-lying section called the vermis. They develop in the cerebellar primordium that covers the fourth ventricle and below a fissure-like region called the isthmus of the developing brain. Purkinje cells migrate toward the outer surface of the cerebellar cortex and form the Purkinje cell layer.

Purkinje cells are born during the earliest stages of cerebellar neurogenesis. Neurogenin2, together with neurogenin1, are transiently expressed in restricted domains of the ventricular neuroepithelium during the time-window of Purkinje cell genesis.^[17] This spatio-temporal distribution pattern suggests that neurogenins are involved in the specification of phenotypically heterogeneous Purkinje cell subsets, ultimately responsible for constructing the framework of the cerebellar topography.

There is evidence in mice and humans that bone marrow cells either fuse with or generate cerebellar Purkinje cells, and it is possible that bone marrow cells, either by direct generation or by cell fusion, could play a role in repair of central nervous system damage.^{[18][19][20][21][22]} Further evidence points yet towards the possibility of a common stem cell ancestor among Purkinje neurons, B-lymphocytes and aldosterone-producing cells of the human adrenal cortex.^[21]

Function

• Simple spikes occur at rates of 17 – 150 Hz (Raman and Bean, 1999), either spontaneously or when Purkinje cells are activated synaptically by the parallel fibers, the axons of the granule cells.
• Complex spikes are slow, 1–3 Hz spikes, characterized by an initial prolonged large-amplitude spike, followed by a high-frequency burst of smaller-amplitude action potentials. They are caused by climbing fiber activation and can involve the generation of calcium-mediated action potentials in the dendrites. Following complex spike activity, simple spikes can be suppressed by the powerful complex spike input.[23]

Purkinje cells show spontaneous electrophysiological activity in the form of trains of spikes both sodium-dependent and calcium-dependent. This was initially shown by

Clinical significance

In humans, Purkinje cells can be harmed by a variety of causes: toxic exposure, e.g. to alcohol or lithium;

Gluten ataxia is an autoimmune disease triggered by the ingestion of gluten.^[39] The death of Purkinje cells as a result of gluten exposure is irreversible. Early diagnosis and treatment with a gluten-free diet can improve ataxia and prevent its progression.^[37][40] Less than 10% of people with gluten ataxia present any gastrointestinal symptom, yet about 40% have intestinal damage.^[40] It accounts for 40% of ataxias of unknown origin and 15% of all ataxias.^[40]

The

Some domestic animals can develop a condition where the Purkinje cells begin to atrophy shortly after birth, called cerebellar abiotrophy. It can lead to symptoms such as ataxia, intention tremors, hyperreactivity, lack of menace reflex, stiff or high-stepping gait, apparent lack of awareness of foot position (sometimes standing or walking with a foot knuckled over), and a general inability to determine space and distance.^[42] A similar condition known as cerebellar hypoplasia occurs when Purkinje cells fail to develop in utero or die off before birth.

The genetic conditions

Etymology

Purkinje cells are named after the Czech scientist Jan Evangelista Purkyně, who discovered them in 1839.^{[citation needed]}

See also

List of distinct cell types in the adult human body

References