) 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
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 more potent than ibotenic acid.
Muscimol is produced naturally in the mushrooms Amanita muscaria, Amanita pantherina, and Amanita gemmata, along with muscarine, muscazone, and ibotenic acid. Of these, only A. muscaria and A. pantherina are considered somewhat safe for human consumption, with the other being far more dangerous; however lethal poisonings have occurred from A. muscaria and A. pantherina as well. , 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.
Muscimol is a potent GABAA agonist
, activating the receptor
for the brain's major inhibitory neurotransmitter
. 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
which bind to a separate regulatory site. 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
, and cerebellum
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 15-20mg for a normal person. . 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.
LD50 mice: 3.8 mg/kg s.c, 2.5 mg/kg i.p.
LD50 rats: 4.5 mg/kg i.v, 45 mg/kg orally.
The effects of muscimol are substantially different from psilocybin
, 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
- 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.
- Beaumont K, Chilton W. S., Yamamura H. I., Enna S. J. (1978). "Muscimol binding in rat brain: association with synaptic GABA receptors". Brain Res. 148 (1): 153–62.
- S. R. Snodgrass (1978). "Use of 3H-muscimol for GABA receptor studies". Nature 273 (1): 392–394.
- G. A. R. Johnston, D. R. Curtis, W. C. de Groat and A. W. Duggan (1968). "Central actions of ibotenic acid and muscimol". Biochemical Pharmacology 17 (12): 2488–2489.