Muscimol

Muscimol (Agarin, Pantherine) is the major psychoactive alkaloid present in many mushrooms of the Amanita genus. Unlike psilocybin, a tryptamine, muscimol is a potent, selective agonist of the GABAA receptor.
==Chemistry==
Amanita muscaria contains two main active ingredients, Ibotenic acid and its derivative Muscimol. Muscimol is the product of the decarboxylation or drying of ibotenic acid and it is thought that muscimol is as much as ten times as potent as ibotenic acid.
== Biology ==
Muscimol is produced naturally in the mushrooms Amanita muscaria, Amanita pantherina, and Amanita gemmata, along with muscarine, muscazone, and ibotenic acid.Chilton WS, Ott J. Toxic metabolites of Amanita pantherina, A. cothurnata, A. muscaria and other Amanita species. Lloydia. 1976 Mar-Jun;39(2-3):150-7. PMID 985999Michelot D, Melendez-Howell LM. Amanita muscaria: chemistry, biology, toxicology, and ethnomycology. Mycological Research. 2003 Feb;107(Pt 2):131-46. PMID 12747324 A. muscaria and A. pantherina are not considered safe for human consumption, poisonings have occurred from A. muscaria and A. pantherina as well.Tupalska-Wilczyńska K, Ignatowicz R, Poziemski A, Wójcik H, Wilczyński G. Poisoning with spotted and red mushrooms--pathogenesis, symptoms, treatment. (Polish). Wiadomosci Lekarskie. 1996;49(1-6):66-71. PMID 9173659 It is thought that, in A. muscaria, the layer just below the skin of the cap contains the highest amount of muscimol, and is therefore the most psychoactive portion.
== Pharmacology ==
Muscimol is a potent GABAA agonist, activating the receptor for the brain's major inhibitory neurotransmitter, GABA. Muscimol actually binds to the same binding site on the GABAA receptor complex as GABA itself, as opposed to other GABAergic drugs such as barbiturates and benzodiazepines which bind to separate regulatory sites.Frølund B, Ebert B, Kristiansen U, Liljefors T, Krogsgaard-Larsen P. GABA(A) receptor ligands and their therapeutic potentials. Current Topics in Medicinal Chemistry. 2002 Aug;2(8):817-32. PMID 12171573 GABAA receptors are widely distributed in the brain, and so when muscimol is administered, it alters neuronal activity in multiple regions including the cerebral cortex, hippocampus and cerebellum.
However while muscimol is conventionally thought of as a selective GABAA agonist, it is also a potent partial agonist at the GABAC receptor, and so its effects profile results from a combined action at both targets.Woodward RM, Polenzani L, Miledi R. Characterization of bicuculline/baclofen-insensitive (rho-like) gamma-aminobutyric acid receptors expressed in Xenopus oocytes. II. Pharmacology of gamma-aminobutyric acidA and gamma-aminobutyric acidB receptor agonists and antagonists. Molecular Pharmacology. 1993 Apr;43(4):609-25. PMID 8386310
During a test involving rabbits connected to an EEG, muscimol showed a distinctly synchronized EEG tracing. This is substantially different from indolic psychedelics, as brainwave patterns will generally show a desynchronization. In higher doses (2mg/kg), the EEG will show characteristic spikes.
When used in vivo, muscimol will pass through the human body, and be excreted (as muscimol) in the subject's urine.
The psychoactive dose of muscimol is around 10-15 mg for a normal person. Erowid Psychoactive Amanitas Vault : Dosage. A Guide to British Psilocybin Mushrooms by Richard Cooper published in 1977 recommends a smaller dose, 8.5mg, and suggests that it is possible for this amount to be present in as little as 1g of dried A.muscaria. It goes on to say that determining a correct dose can be difficult as potency varies dramatically from one mushroom to the next.
== Toxicity ==
LD50 mice: 3.8 mg/kg s.c, 2.5 mg/kg i.p.Erowid Psychoactive Amanitas Vault : Chemistry
LD50 rats: 4.5 mg/kg i.v, 45 mg/kg orally.Erowid Psychoactive Amanitas Vault : Chemistry
== Effects ==
The effects of muscimol are substantially different from Psilocybe mushroom alkaloids, as the chemicals target separate parts of the brain. Muscimol has been shown to lack "structured" hallucinations in most cases, and the effects are frequently compared to a lucid dream state. The hallucinogenic effect produced by muscimol is most closely comparable to the hallucinogenic side effects produced by some other GABAergic drugs such as zolpidem.
== See also ==
* Amanita muscaria
== References ==
* Merck Index, 12th Edition
* Ito Y, Segawa K, Fukuda H. 1995 "Functional diversity of GABAA receptor ligand-gated chloride channels in rat synaptoneurosomes" Synapse 19(3):188-96.
* Rätsch, Christian. (1998). The Encyclopedia of Psychoactive Plants. Rochester, VT: Park Street Press.
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==External links==
*Psychoactive Amanitas on Erowid
Category:Entheogens