What is Ayahuasca?
The word "Ayahuasca" refers to a medicinal and magical drink incorporating two or more distinctive plant species capable of producing profound mental, physical and spiritual effects when brewed together and consumed in a ceremonial setting. One of these plants is always the giant woody liana vine called ayahuasca (Banisteriopsis caapi or other species). The other plant or plants combined with ayahuasca generally contain tryptamine alkaloids, most often dimethyltryptamine (DMT).

The plants most often used are the leaves of chacruna (Psychotria viridis and other species) and oco yagé; also known as chalipanga, chagraponga, and huambisa (Diplopterys cabrerana). This drink is widely employed throughout Amazonian Perú, Ecuador, Colombia, Bolivia, western Brazil, and in portions of the Río Orinoco basin. It has probably been used in the western Amazon for millennia and is rapidly expanding in South America and elsewhere through the growth of organized syncretic religious movements such as Santo Daime, União do Vegetal (UDV), and Barquinia, among others.

In traditional rainforest practice, other medicinal or visionary plants are often added to the brew for various purposes, from purely positive healing (blancura) and divination to malevolent black magic (brujeria, magia negra or rojo). The oldest known object related to the use of ayahuasca is a ceremonial cup, hewn out of stone, with engraved ornamentation, which was found in the Pastaza culture of the Ecuadorean Amazon from 500 B.C. to 50 A.D. It is deposited in the collection of the Ethnological Museum of the Central University (Quito, Ecuador). This indicates that ayahuasca potions were known and used at least 2,500 years ago. Its antiquity in the lower Amazon is likely much greater.

The Ayahuasca medicine usually contains both beta-carboline and tryptamine alkaloids. However, some indigenous Amazonian cultures, i.e. Yahua and others, prepare a ceremonial drink from the ayahuasca vine alone. The effects differ in visionary qualities from the more typical composite preparation but with the same profound cleansing and spiritual effects. The beta-carbolines (harmine, harmaline, and tetrahydroharmine) are obtained from the ayahuasca vine (Banisteriopsis caapi). Harmine and harmaline are visionary at near toxic levels, but at modest dosage typically produce mainly tranquility and purgation. Tetrahydroharmine is present in significant levels in ayahuasca. It may be responsible for some of its more profound effects compared to analogue plants such as Syrian rue (Peganum harmala).

The ratio of these harmala alkaloids in ayahuasca varies greatly from one geographical area to another in the Amazon basin. The proportions in which they are present likely accounts for the varied effects reported by shamans from different 'kinds' of ayahuasca even though all are botanically classified as Banisteriopsis caapi.

Harmala alkaloids are short term monoamine oxidase inhibitors which render tryptamines orally active by temporarily reducing levels of monoamine oxidase in the body which otherwise rapidly destroys them. The combination of specific serotonin reuptake inhibitors (SSRIs, such as Prozac), and most other antidepressants, with Ayahuasca or other MAO inhibitors can cause life support emergencies or death.

The principal ayahuasca compounds have a common indole structure which, through several mechanisms, influences certain functions of the central nervous system (CNS). The relevant factor is the biochemical similarity of these compounds to the neurotransmitter serotonin (5-HT). The harmala alkaloids in ayahuasca, primarily harmine and tetrahydroharmine, reversibly inhibit the neuronal enzyme monoamine oxidase (MAO). This allows DMT to be active when ingested orally. It also facilitates accumulation of biogenic amines, such as 5-HT, which are normally metabolized by monoamine oxidase enzymes.

DMT is a naturally-occurring biochemical substance secreted by the human body in the pineal gland. It occurs in hundreds of plant species worldwide. It can produce very powerful visionary effects when smoked in its pure form or taken orally in Ayahuasca.