A giant depolarizing potential (GDP) is a type of patterned spontaneous activity that can be observed in preparations of developing

brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

at early stages of development. These patterns of activity differ a lot from both the adult brain activity, and

epileptiform Epilepsy is a group of non-communicable neurological disorders characterized by a tendency for recurrent, unprovoked seizures. A seizure is a sudden burst of abnormal electrical activity in the brain that can cause a variety of symptoms, rang ...

activity. In

human Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...

s they exist only on

prenatal Prenatal development () involves the embryonic development, development of the embryo and of the fetus during a viviparity, viviparous animal's gestation. Prenatal development starts with fertilization, in the germinal stage of embryonic develop ...

stages, in

rat Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include '' Neotoma'' (pack rats), '' Bandicota'' (bandicoo ...

s they last for approximately P6. GDPs were postulated to be essential for the establishment and maturation of synaptic connections in the immature brain . One of the main conditions for GDP development (that is met in premature but not adult brain) is that

GABA GABA (gamma-aminobutyric acid, γ-aminobutyric acid) is the chief inhibitory neurotransmitter in the developmentally mature mammalian central nervous system. Its principal role is reducing neuronal excitability throughout the nervous system. GA ...

action on these stages should be

excitatory In neuroscience, an excitatory postsynaptic potential (EPSP) is a postsynaptic potential that makes the postsynaptic neuron more likely to fire an action potential. This temporary depolarization of postsynaptic membrane potential, caused by the ...

rather than

inhibitory An inhibitory postsynaptic potential (IPSP) is a kind of synaptic potential that makes a Chemical synapse, postsynaptic neuron less likely to generate an action potential.Purves et al. Neuroscience. 4th ed. Sunderland (MA): Sinauer Associates, Inc ...

. This is caused by a much higher concentration of Cl⁻ concentration in the

cytoplasm The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...

of neonatal neurons. Further, the expression of the chloride transporter, KCC2, is less in immature neurons, as a result of which there is the above-mentioned high intracellular chloride. On receiving a GABAergic stimulus, there is an efflux of Chloride from the cell, resulting in depolarization of the cell. This causes the GDPs. Once the KCC2 expression is relatively high, as in the adult, mature neurons, the GDPs almost simultaneously disappear. The increased level of KCC2 expression in adult, mature neurons alone is not the reason for the disappearance of the GDPs, however.

References

{{Reflist Developmental neuroscience