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= Psilocybe =
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Introduction
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'Psilocybe' ( ) is a genus of gilled mushrooms, growing worldwide, in
the family Hymenogastraceae. Most or nearly all species contain the
psychedelic compounds Psilocybin, psilocin and baeocystin.
Etymology
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The word 'Psilocybe' comes from the Greek words ψιλός + κύβη, and
literally means "bare headed", referring to the mushroom's detachable
pellicle (loose skin over the cap).
Description
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'Psilocybe' fruit bodies are typically small, nondescript mushrooms
with a typical "little brown mushroom" morphology. Macroscopically,
they are characterized by their small to occasionally medium size,
brown to yellow-brown coloration, with a typically hygrophanous cap,
and a spore print-color that ranges from lilac-brown to dark
purple-brown (though rusty-brown colored varieties are known in at
least one species). Hallucinogenic species typically have a
blue-staining reaction when the fruit body is bruised.
Microscopically, they are characterized by pileipellis with hyphae
that run parallel to the pileus surface, forming a 'cutis', by their
lack of chrysocystidia, and by spores that are smooth, ellipsoid to
rhomboid to subhexagonal in shape, with a distinct apical germ pore.
Ecologically, all species of 'Psilocybe' are saprotrophs, growing on
various kinds of decaying organic matter.
Classification
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A 2002 study of the molecular phylogeny of the agarics indicated that
the genus 'Psilocybe' as then defined was polyphyletic, falling into
two distinct clades that are not directly related to each other. The
blue-staining hallucinogenic species constituted one clade and the
non-bluing species the other. The previous type species ('Psilocybe ')
of the genus was in the non-bluing clade, but in 2010 the type species
was changed to 'Psilocybe semilanceata', a member of the bluing clade.
A 2006 molecular phylogenetic study of the Agaricales by Matheny and
colleagues, further demonstrated the separation of the bluing and
non-bluing clades of 'Psilocybe' in a larger, strongly supported
phylogenetic tree of the Agaricales.
'Psilocybe' had been placed taxonomically in the agaric family
Strophariaceae based upon its spore and pileipellis morphology. The
phylogenetic study by Matheny 'et al.', placed the non-bluing
'Psilocybe' and its close relatives in a basal position within the
Strophariaceae, a sister taxon to a clade containing the other genera
within that family. The bluing 'Psilocybe', however, form a clade that
is sister to 'Galerina' in the newly revised family, Hymenogastraceae
that used to be restricted to secotioid, false-truffles. The
phylogenetic study by Moncalvo, 'et al.' confirmed that the agaric
genus 'Melanotus' is simply a subgroup of the non-bluing 'Psilocybe',
all of which are placed in 'Deconica', and also pointed to a close
relationship between the latter genus and the genera 'Kuehneromyces'
and 'Phaeogalera'.
In 2007, a paper by Redhead 'et al.' proposed conserving the genus
'Psilocybe' with 'Psilocybe semilanceata' as its type species. The
suggestion was accepted by unanimous vote of the Nomenclature
Committee for Fungi of the International Botanical Congress in 2010,
meaning that 'P. semilanceata' (a member of the bluing clade) now
serves as the type species of the genus. Since 'P. semilanceata' is
now the type species of the genus, the bluing hallucinogenic clade
remained in the genus 'Psilocybe' (Hymenogastraceae) while the
non-bluing clade were transferred to the genus 'Deconica'
(Strophariaceae). However, it has been demonstrated that 'Psilocybe
fuscofulva', a species that used to be known as 'Psilocybe
atrobrunnea', belongs to the genus 'Psilocybe' s.s. but does not
contain psychotropic compounds.
Distribution and habitat
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Geographically, species in this genus are found throughout the world
in most biomes. The greatest species diversity seems to be in the
neotropics, from Mesoamerica through Brazil and Chile. 'Psilocybe' are
found in a variety of habitats and substrates. Many of the species
found in temperate regions, such as 'Psilocybe cyanescens', seem to
have an affinity for landscaped areas mulched with woodchips and are
actually rather rare in natural settings removed from human
habitation. Contrary to popular belief, only a minority of 'Psilocybe'
species, such as 'P. cubensis' and 'P. subcubensis', grow directly on
feces. Many other species are found in habitats such as mossy, grassy,
or forest humus soils.
Biochemistry and pharmacology
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The psilocybin molecule is indirectly responsible for the
hallucinogenic properties of the 'Psilocybe'. This compound, as well
as all other indole alkaloids, are derived from the amino acid
tryptophan, being the only amino acid with the indole-amine ring.
Tryptophan is converted to tryptamine by decarboxylation. Two
methylation steps occur producing DMT, another psychedelic compound.
Hydroxylation of this compound produces the more potent hallucinogen
psilocin, followed by phosphorylation yielding psilocybin. After
ingestion of the psilocybin compound alkaline phosphatases present in
the body's digestive system, kidneys, and possibly in the blood
readily cleave the phosphoryl ester bond from psilocybin, yielding the
hydroxyl compound, psilocin. Psilocin is the chemical primarily
responsible for the hallucinogenic effects of the 'Psilocybe'. The
blue-staining species of 'Psilocybe' are characterized by the presence
of psilocin and psilocybin. This blue-staining reaction occurs after
the fruit body has been injured, particularly near the base of the
stalk. This reaction is thought to be due to the oxidation of
psilocybin after the outer surface of the fruit body has been
breached. The degree of bluing in a 'Psilocybe' fruit body roughly
correlates with the concentration of psilocin in the mushroom.
Psilocybin is chemically far more stable than psilocin, the latter
compound being largely lost when the mushroom is heated or dried.
The chemical structure of serotonin, an innate indole alkaloid
neurotransmitter that regulates our mood and therefore happiness, is
nearly identical to that of psilocin. The latter differing mainly by
the hydroxyl group moving one carbon and the addition of two methyl
groups that make the molecule lipophilic (fat soluble), ergo capable
of crossing the lipid membrane sheaths of the central nervous system.
After psilocybin has been ingested and dephosphorylated, to psilocin,
the mechanism it uses in the brain has a direct agonist effect on the
5-HT serotonin receptors. To explain this effect, the psilocin
molecule essentially mimics the serotonin molecule, binding to the
5-HT receptors and initiating the same response as the serotonin. This
effect explains the euphoria experienced by ingestion of this
"agonist." Initially, hallucinogens were thought to blockade these
serotonin neurotransmitters, but persistent research led to this
agonist effect conclusion.
Woolley and Campbell conducted research to determine whether the
depletion of the hormone serotonin had a direct effect on mental
disorders and that hallucinations might be due to an excess of
serotonin. Their results led them to study chemicals analogous to
serotonin. They found that the psychoactive chemicals psilocybin and
psilocin exhibited serotonin-like effects, however as dosage
increased, these compounds acted as serotonin antagonists, psilocybin
being comparable to the most potent antagonist yet discovered. This
is a plausible basis for the psychological effects of these
hallucinogenic compounds.
Even though these chemicals are psychoactive and therefore the
basidiomycete deemed toxic, there have been no reports of fatalities
or induced internal organ damage directly associated with ingestion of
these chemicals. Misidentification of the fruit body could lead to
ingestion of a lethal fungus.
Some psychoactive species contain baeocystin, norbaeocystin and
β‐carboline monoamine oxidase inhibitors in addition to psilocin and
psilocybin.
Medical and psychiatric aspects
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The medicinal uses of the 'Psilocybe' was recorded by Native Americans
of Central America. Shamans, or curanderas would avidly ingest the
"sacred mushrooms" for the extrasensory perceptual effects it gave
them in order to better assess problems faced in their society. The
observed effects of the alkaloids found in these mushrooms has given
rise to research into their possible uses for psychiatric medicine.
For details on contemporary research, see: Psilocybin: Medical
research.
History and ethnography
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Hallucinogenic species of 'Psilocybe' have a long history of use among
the native peoples of Mesoamerica for religious communion, divination,
and healing, from pre-Columbian times up to the present day.
Hallucinogenic 'Psilocybe' were known to the aboriginal Mexicans as
'teonanácatl' (literally "divine mushroom") and were reportedly served
at the coronation of Moctezuma II in 1502. After the Spanish conquest
of the Americas, the use of hallucinogenic plants and mushrooms, like
other pre-Christian traditions, was forcibly suppressed and driven
underground.
By the 20th century, hallucinogenic mushroom use was thought by
non-Native Americans to have disappeared entirely. However, in 1955,
Valentina Wasson and R. Gordon Wasson became the first Westerners to
actively participate in an indigenous mushroom ceremony. The Wassons
did much to publicize their discovery, even publishing an article on
their experiences in 'Life' in 1957. In 1956, Roger Heim identified
the hallucinogenic mushroom that the Wassons had brought back from
Mexico as 'Psilocybe' and in 1958, Albert Hofmann first reported
psilocin and psilocybin as the active compound in these mushrooms.
There is some skepticism as to whether or not these "sacred
mushrooms" were actually in the genus 'Psilocybe'. However, according
to Heim's research in Mexico, he identified three species of
'Psilocybe' that he believed were used in these native ceremonies. The
species identified by Heim were; 'Psilocybe mexicana, P.
caerulescens', and 'P. zapotecorum'. are a variety of 'Psilocybe'
mushrooms that make up the 'teonanácatl' group of hallucinogenic
mushrooms, including 'Psilocybe cubensis'. Isauro Nava Garcia, a
Mazotec man, provided guidance to Heim while Heim conducted his field
and culture work. Garcia was an avid observer of the fungi in his
environment while identifying specific characteristics about the fruit
body of the 'Psilocybe' his ancestors utilized, as well as knowing
where they could be found.
At present, hallucinogenic mushroom use has been reported among a
number of groups spanning from central Mexico to Oaxaca, including
groups of Nahua, Mixtecs, Mixe, Mazatecs, Zapotecs, and others.
The popularization of entheogens by Wasson, Timothy Leary, and others
has led to an explosion in the use of hallucinogenic 'Psilocybe'
throughout the world. By the early 1970s, a number of psychoactive
'Psilocybe' species were described from temperate North America,
Europe, and Asia and were widely collected. Books describing methods
of cultivating 'Psilocybe cubensis' in large quantities were also
published. The relatively easy availability of hallucinogenic
'Psilocybe' from wild and cultivated sources has made it among the
most widely used of the hallucinogenic drugs.