isoquinoline
Isoquinoline is an individual chemical specimen - a heterocyclic aromatic organic compound - as well as the name of a family of many thousands of natural plant alkaloids, any one of which might be referred to as "an isoquinoline". It is a struc ...
compound that is a light-sensitive competitive
antagonist
An antagonist is a character in a story who is presented as the main enemy or rival of the protagonist and is often depicted as a villain.GABAA receptors. It was originally identified in 1932 in plant
alkaloid
Alkaloids are a broad class of natural product, naturally occurring organic compounds that contain at least one nitrogen atom. Some synthetic compounds of similar structure may also be termed alkaloids.
Alkaloids are produced by a large varie ...
extracts and has been isolated from ''
Dicentra cucullaria
''Dicentra cucullaria'', Dutchman's britches, or Dutchman's breeches, is a perennial herbaceous plant, native to rich woods of eastern North America, with a disjunct population in the Columbia Basin.
The common name Dutchman's breeches derive ...
Corydalis
''Corydalis'' (from Greek ''korydalís'' " crested lark") is a genus of about 540 species of annual and perennial herbaceous plants in the family Papaveraceae, native to the temperate Northern Hemisphere and the high mountains of tropical ...
'' species (all in
subfamily
In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...
Fumarioideae
Fumarioideae is a subfamily of the family Papaveraceae (the poppy family). It was formerly treated as a separate family, the Fumariaceae (the fumitory, fumewort or bleeding-heart family). It consists of about 575 species of herbaceous plants in 20 ...
, previously known as
family
Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Fumariaceae). Since it blocks the inhibitory action of GABA receptors, the action of bicuculline mimics
epilepsy
Epilepsy is a group of Non-communicable disease, non-communicable Neurological disorder, neurological disorders characterized by a tendency for recurrent, unprovoked Seizure, seizures. A seizure is a sudden burst of abnormal electrical activit ...
; it also causes
convulsion
A convulsion is a medical condition where the body muscles contract and relax rapidly and repeatedly, resulting in uncontrolled shaking. Because epileptic seizures typically include convulsions, the term ''convulsion'' is often used as a synony ...
s. This property is utilized in laboratories around the world in the ''in vitro'' study of epilepsy, generally in
hippocampal
The hippocampus (: hippocampi; via Latin from Greek , 'seahorse'), also hippocampus proper, is a major component of the brain of humans and many other vertebrates. In the human brain the hippocampus, the dentate gyrus, and the subiculum ar ...
or cortical neurons in prepared brain slices from rodents. This compound is also routinely used to isolate
glutamatergic
Glutamatergic means "related to glutamate". A glutamatergic agent (or drug) is a chemical that directly modulates the excitatory amino acid (glutamate/aspartate) system in the body or brain. Examples include excitatory amino acid receptor agonist ...
(excitatory amino acid) receptor function.
The action of bicuculline is primarily on the
ionotropic
Ligand-gated ion channels (LICs, LGIC), also commonly referred to as ionotropic receptors, are a group of transmembrane ion-channel proteins which open to allow ions such as Na+, K+, Ca2+, and/or Cl− to pass through the membrane in res ...
ion
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
channels concerned chiefly with the passing of chloride ions across the cell membrane, thus promoting an inhibitory influence on the target
neuron
A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...
. These receptors are the major targets for
benzodiazepines
Benzodiazepines (BZD, BDZ, BZs), colloquially known as "benzos", are a class of central nervous system (CNS) depressant drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. They are prescribed to treat co ...
,
z-drugs
Nonbenzodiazepines (), sometimes referred to colloquially as Z-drugs (as many of their names begin with the letter "z"), are a class of psychoactive, depressant, sedative, hypnotic, anxiolytic drugs that are benzodiazepine-like in uses, such as f ...
, and related
anxiolytic
An anxiolytic (; also antipanic or anti-anxiety agent) is a medication or other intervention that reduces anxiety. This effect is in contrast to anxiogenic agents which increase anxiety. Anxiolytic medications are used for the treatment of anxie ...
drugs.
The half-maximal inhibitory concentration ( IC50) of bicuculline on GABAA receptors is 3 μM.
In addition to being a potent GABAA receptor antagonist, bicuculline can be used to block Ca2+-activated potassium channels.
Sensitivity to bicuculline is defined by IUPHAR as a major criterion in the definition of GABAA receptors