Ifenprodil, sold under the brand names Cerocral, Dilvax, and Vadilex, is a cerebral vasodilator that has been marketed in some countries, including in Japan, Hong Kong, and France.[1][2][3][4] It is currently under development for treatment of a variety of additional indications.[5]
The N-methyl-D-aspartatereceptor (also known as the NMDA receptor or NMDAR), is a glutamate receptor and predominantly Ca2+ ion channel found in neurons. The NMDA receptor is one of three types of ionotropic glutamate receptors, the other two being AMPA and kainate receptors. Depending on its subunit composition, its ligands are glutamate and glycine (or D-serine). However, the binding of the ligands is typically not sufficient to open the channel as it may be blocked by Mg2+ ions which are only removed when the neuron is sufficiently depolarized. Thus, the channel acts as a "coincidence detector" and only once both of these conditions are met, the channel opens and it allows positively charged ions (cations) to flow through the cell membrane. The NMDA receptor is thought to be very important for controlling synaptic plasticity and mediating learning and memory functions.
Dizocilpine (INN), also known as MK-801, is a pore blocker of the NMDA receptor, a glutamate receptor, discovered by a team at Merck in 1982. Glutamate is the brain's primary excitatory neurotransmitter. The channel is normally blocked with a magnesium ion and requires depolarization of the neuron to remove the magnesium and allow the glutamate to open the channel, causing an influx of calcium, which then leads to subsequent depolarization. Dizocilpine binds inside the ion channel of the receptor at several of PCP's binding sites thus preventing the flow of ions, including calcium (Ca2+), through the channel. Dizocilpine blocks NMDA receptors in a use- and voltage-dependent manner, since the channel must open for the drug to bind inside it. The drug acts as a potent anti-convulsant and probably has dissociative anesthetic properties, but it is not used clinically for this purpose because of the discovery of brain lesions, called Olney's lesions (see below), in laboratory rats. Dizocilpine is also associated with a number of negative side effects, including cognitive disruption and psychotic-spectrum reactions. It inhibits the induction of long term potentiation and has been found to impair the acquisition of difficult, but not easy, learning tasks in rats and primates. Because of these effects of dizocilpine, the NMDA receptor pore blocker ketamine is used instead as a dissociative anesthetic in human medical procedures. While ketamine may also trigger temporary psychosis in certain individuals, its short half-life and lower potency make it a much safer clinical option. However, dizocilpine is the most frequently used uncompetitive NMDA receptor antagonist in animal models to mimic psychosis for experimental purposes.
The metabotropic glutamate receptors, or mGluRs, are a type of glutamate receptor that are active through an indirect metabotropic process. They are members of the group C family of G-protein-coupled receptors, or GPCRs. Like all glutamate receptors, mGluRs bind with glutamate, an amino acid that functions as an excitatory neurotransmitter.
Glutamate receptors are synaptic and non synaptic receptors located primarily on the membranes of neuronal and glial cells. Glutamate is abundant in the human body, but particularly in the nervous system and especially prominent in the human brain where it is the body's most prominent neurotransmitter, the brain's main excitatory neurotransmitter, and also the precursor for GABA, the brain's main inhibitory neurotransmitter. Glutamate receptors are responsible for the glutamate-mediated postsynaptic excitation of neural cells, and are important for neural communication, memory formation, learning, and regulation.
NMDA receptor antagonists are a class of drugs that work to antagonize, or inhibit the action of, the N-Methyl-D-aspartate receptor (NMDAR). They are commonly used as anesthetics for humans and animals; the state of anesthesia they induce is referred to as dissociative anesthesia.
Glutamate [NMDA] receptor subunit zeta-1 is a protein that in humans is encoded by the GRIN1 gene.
Neramexane is a drug related to memantine, which acts as an NMDA antagonist and has neuroprotective effects. It is being developed for various possible applications, including treatment of tinnitus, Alzheimer's disease, drug addiction and as an analgesic. Animal studies have also suggested antidepressant and nootropic actions so that this drug may be used for a wide range of potential applications. It also acts as a nicotinic acetylcholine receptor antagonist.
CGP-37849 is a competitive antagonist at the NMDA receptor. It is a potent, orally active anticonvulsant in animal models, and was researched for the treatment of epilepsy. It also has neuroprotective activity and shows antidepressant and anxiolytic effects.
PEAQX is a competitive antagonist at the NMDA receptor. Although originally described as 100-fold selective for GluN1/GluN2A receptors vs. GluN1/GluN2B receptors, more detailed studies of the Ki of PEAQX revealed it only shows a 5 fold difference in affinity for GluN1/GluN2A vs. GluN1/GluN2B receptors. It is also a potent anticonvulsant in animal tests.
2-Methyl-6-(phenylethynyl)pyridine (MPEP) is a research drug which was one of the first compounds found to act as a selective antagonist for the metabotropic glutamate receptor subtype mGluR5. After being originally patented as a liquid crystal for LCDs, it was developed by the pharmaceutical company Novartis in the late 1990s. It was found to produce neuroprotective effects following acute brain injury in animal studies, although it was unclear whether these results were purely from mGluR5 blockade as it also acts as a weak NMDA antagonist, and as a positive allosteric modulator of another subtype mGlu4, and there is also evidence for a functional interaction between mGluR5 and NMDA receptors in the same populations of neurons. It was also shown to produce antidepressant and anxiolytic effects in animals, and to reduce the effects of morphine withdrawal, most likely due to direct interaction between mGluR5 and the μ-opioid receptor.
Arylcyclohexylamines, also known as arylcyclohexamines or arylcyclohexanamines, are a chemical class of pharmaceutical, designer, and experimental drugs.
Dextrallorphan (DXA) is a chemical of the morphinan class that is used in scientific research. It acts as a σ1 receptor agonist and NMDA receptor antagonist. It has no significant affinity for the σ2, μ-opioid, or δ-opioid receptor, or for the serotonin or norepinephrine transporter. As an NMDA receptor antagonist, in vivo, it is approximately twice as potent as dextromethorphan, and five-fold less potent than dextrorphan.
Traxoprodil is a drug developed by Pfizer which acts as an NMDA antagonist, selective for the NR2B subunit. It has neuroprotective, analgesic, and anti-Parkinsonian effects in animal studies. Traxoprodil has been researched in humans as a potential treatment to lessen the damage to the brain after stroke, but results from clinical trials showed only modest benefit. The drug was found to cause EKG abnormalities and its clinical development was stopped. More recent animal studies have suggested traxoprodil may exhibit rapid-acting antidepressant effects similar to those of ketamine, although there is some evidence for similar psychoactive side effects and abuse potential at higher doses, which might limit clinical acceptance of traxoprodil for this application.
Metaphit is a research chemical that acts as an acylator of NMDARAn, sigma and DAT binding sites in the CNS. It is the m-isothiocyanate derivative of phencyclidine (PCP) and binds irreversibly to the PCP binding site on the NMDA receptor complex. However, later studies suggest the functionality of metaphit is mediated by sites not involved in PCP-induced passive avoidance deficit, and not related to the NMDA receptor complex. Metaphit was also shown to prevent d-amphetamine induced hyperactivity, while significantly depleting dopamine content in the nucleus accumbens. Metaphit was the first acylating ligand used to study the cocaine receptor. It is a structural isomer of the similar research compound fourphit, as it and metaphit both are isothiocyanate substituted derivatives of an analogous scaffold shared with PCP.
BD1008 or N-[2-(3,4-dichlorophenyl)ethyl]-N-methyl-1-pyrrolidineethanamine is a selective sigma receptor antagonist, with a reported binding affinity of Ki = 2 ± 1 nM for the sigma-1 receptor and 4 times selectivity over the sigma-2 receptor.
HA-966 or (±)-3-amino-1-hydroxy-pyrrolidin-2-one is a molecule used in scientific research as a glycine receptor and NMDA receptor antagonist / low efficacy partial agonist. It has neuroprotective and anticonvulsant, anxiolytic, antinociceptive and sedative / hypnotic effects in animal models. Pilot human clinical trials in the early 1960s showed that HA-966 appeared to benefit patients with tremors of extrapyramidal origin.
3-Hydroxyphencyclidine (3-HO-PCP) is a dissociative of the arylcyclohexylamine class related to phencyclidine (PCP) that has been sold online as a designer drug.
Pregnenolone succinate is a synthetic pregnane steroid and an ester of pregnenolone which is described as a glucocorticoid and anti-inflammatory drug and has been patented and marketed as a topical medication in the form of a cream for the treatment of allergic, pruritic, and inflammatory dermatitis. It has also been described as a non-hormonal sterol, having neurosteroid activity, and forming a progesterone analogue via dehydrogenation.
PD-137889 (N-methylhexahydrofluorenamine) is a chemical compound that is active as an NMDA receptor antagonist in the central nervous system at roughly 30 times the potency of the "flagship" of its class, ketamine, and substitutes for phencyclidine in animal studies. Ki [3H]TCP binding = 27 nM versus ketamine's Ki = 860 nM.
CGP-39551 is a drug used in scientific research, it is investigated as an anti-convulsant.
References
1 2 The Merck Index (Thirteenthed.). Whitehouse Station, NJ: Merck Research Laboratories Division of Merck & Co., Inc. 2001. p.878.
↑ Reynolds IJ, Miller RJ (November 1989). "Ifenprodil is a novel type of N-methyl-D-aspartate receptor antagonist: interaction with polyamines". Molecular Pharmacology. 36 (5): 758–765. PMID2555674.
↑ Korinek M, Kapras V, Vyklicky V, Adamusova E, Borovska J, Vales K, etal. (December 2011). "Neurosteroid modulation of N-methyl-D-aspartate receptors: molecular mechanism and behavioral effects". Steroids. 76 (13): 1409–1418. doi:10.1016/j.steroids.2011.09.002. PMID21925193. S2CID195681796.
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