Sex is the one aspect of human life that has always held a position of prominence in every time and within every culture nearly without exception. It is a biological imperative of the species. It can be assured that humans have always and will always search for methods to induce sexual arousal, heighten their sexual experience and improve their performance. Aphrodisiacs are substances which are ingested, applied topically, smoked snorted or otherwise delivered into the body to aid in achieving these goals. A huge number of the plants, minerals and synthetic compounds that exist in this world have been labeled aphrodisiac. Throughout history, preparation ingredients have included everything from frogs and berries to sterile, lab synthesized drugs. References to such substances have crept into holy texts from the kama sutra and the Bible to the Koran and in literature from Shakespeare and Ovid to Gilbert and Sullivan plays in the twentieth century (Wedeck, 1963). Mandrake figures prominently in the book of Genesis. Rachel, Jacob's first wife, allows Leah to sleep with Rachel in exchange for mandrake implying that mandrake had some use as an aphrodisiac or possibly as a treatment for fertility. Ovid actually wrote a work called Remedia Amoris, or Remedies for Love detailing specific recipes.
What characteristics qualify a drug or food as an aphrodisiac? Through history, a wide range of characteristics have qualified different substances for this unique category. There are two possible approaches to this question, cultural and scientific. Several primary non-scientific themes have arisen that have echoed through multiple cultures and times. First, genitals of animals have often been deemed aphrodisiac. Cave drawings depict hunters consuming specific parts of their prey in order to gain the characteristics that those organs represented. The Kama Sutra suggests that one boils the testicle of a ram or goat and add milk and sugar before consumption. Even today, female veterinary students in Bristol, England wear the os penis of the dog as a charm. Second, many substances simply resembled human genitalia. In Elizabethan England it was believed that plants with any phallic features like asparagus, parsnips and carrots were certain to be aphrodisiac in their effects. Ukrainians celebrate carrots and celery as folk aphrodisiacs. In Chinese culture much of the aphrodisiac power of ginseng and rhinoceros horn comes from their appearance rather than their chemical composition. Some substances like the root of St. John's Wort and unicorn horns were so aphrodisiacal as a result of this resemblance that they were not even consumed, but simply worn as charms.
However, behind this vast mythology there also exists an honest biological basis for human sexual arousal and a scientific explanation for why many of these compounds give people a rise. Despite the saturation of the concept of the aphrodisiac in nearly all human cultures in history, the scientific community has been reluctant to turn its powerful eye onto the subject. The puritanical value system of western culture has turned a blind eye and has only recently begun to explore even medically diagnosed sexual dysfunctions. Consequently, the body of research on both sexual arousal and the effects of food and drugs on sexual arousal is slim. Most data collected on the effects of drugs and food has arisen from information published about side effects of drugs designed for other purposes or in the specific area of male erectile dysfunction. The dearth of research on the chemistry of sexual arousal only compounds these difficulties. However, the growing field of sex research has spawned a more specific field called pharmacosexology targeted at studying the effects, both positive and negative, of various substances on sexual arousal . This paper offers a general outline of the purported aphrodisiacs that make up a large portion of the foundation of this new field.
The compounds considered here constitute a general sampling of purported aphrodisiacs with identified mechanisms of action. They have been divided into three categories based on their mechanism of action. The entire pool of biologically significant aphrodisiacs can be divided into three primary categories. First, some aphrodisiacs simply provide a burst of nutritional value, improving the immediate health or well-being of the consumer and consequently improving sexual performance and libido. Second, a group of purported aphrodisiacs have more specific physiological effects but are not psychologically active. They may affect blood flow, mimic the burning or "fire" of sex and intercourse or increase the duration of sexual activity by numbing the genital area. The third and final group of aphrodisiacs is made up of compounds that are psycho-pharmacological, that is they actually cross the blood brain barrier and mimic or stimulate some area of sexual arousal. This last category includes a wide range of neurotransmitters, hormones, pheromones, and drugs that mimic or interfere with the normal function of these molecules.
It is reasonable to suggest that proper nutrition and an appropriate balance of nutrients in the diet can promote a general health and well-being in individuals. This simple improvement in general health can lead to a burst of energy and translate into increased sexual appetite. For example, in Hindu tradition, the Kama Sutra describes a "nectar-like" concoction considered a "preservative of life" made up of ghee (clarified butter), honey, sugar, licorice, fennel, and milk (WWW 1). Such a mixture would provide a significant amount of nutrient value and nourishment to the average Hindu at the time of the Kama Sutra. In Chinese tradition, the root of the use of rhinoceros horn as an aphrodisiac may also lie in simple facts of nutritional needs among people at the time. Beyond the fact that rhino horn visually resembles an erect penis, rhino horn also consists of fibrous tissue with large proportions of the elements calcium and phosphorus. Deficiency in these areas lead to muscle weakness and general fatigue. Large doses of these elements in the phase of shortage would lead to a general increase in vigor and stamina. Although this effect could be pronounced enough to deem certain substances aphrodisiacal, well fed humans of the modern world are unlikely to observe the same benefits (Taberner 1985).
A second group of aphrodisiacs are physiologically active beyond the simple nutritional value of the aphrodisiacs described above. The infamous Spanish fly enjoys a long lived reputation as an aphrodisiac. The Roman empress Livia (58 BC - 29 AD) even slipped Spanish fly into the food of other members of the imperial family in hopes of catching them later in sexual indiscretions which could be used against them. The Marquis de Sade often included Spanish fly in the adventures documented in his novels.
Spanish fly is actually made up of dried and crushed beetles of the Cantharis and Mylabris genus' and the Lytta vesicatoria from the Mediterranean, the mid-east and from the British Isles. This preparation contains between 0.4 and 10f the active ingredient in Spanish fly, a crystallized lactone called cantharidin. Cantharidin taken orally in relatively small doses causes an intense burning sensation in the mouth and throat, abdominal cramps, vomiting, diarrhea, painful bloody urination and potential kidney failure. Applied topically, cantharidin again causes a burning sensation to the point of causing blistering and has been used more practically as a wart remover. Also, in some instances the increased blood flow in the body resulting from the consumption of cantharidin actually causes priapism, or prolonged penile erection. However, it is worth noting that this erection is not accompanied by an elevated level of sexual arousal.
Although it seems unlikely to have any aphrodisiacal effects in the light of that description, it has been hypothesized that Spanish fly gained its reputation as a result of its simulation of the "flame" and "passion" of sex (Taberner 1985). Similarly, other compounds that elicit burning sensations, especially various sorts of pepper and paprika have also been considered to have aphrodisiacal qualities. A wide range of aphrodisiacs marketed in the 1970s followed this theme. The "Pseudo Spanish Fly" contained vitamin C, sugar and Spanish pepper (capsicum). "Jungle Love" tablets, "Pseudo-energizers and the "Original Vice-Spice" all primarily contained red pepper. "Pseudo Hard-On Drops" were a combination of licorice root, ginseng, niacin and paprika.
Beyond creating passion-like, inflammatory physiological responses, other reported aphrodisiacs are actually predicted to work by desensitizing the genitals. Several plant products containing the chemicals scopolamine and atropine, two muscarinic acetlycholine receptor antagonists, have been used as sexual aids in the past: deadly nightshade (Atropa belladonna), henbane (Hyoscyamus niger), and two plants referred to as mandrake in historical literature the mandrake root (Mandragora officinalis) and the white thorn apple of India or jimson weed in the United States (Datura stramonium). Scopolamine and atropine are examples of parasympatholytics. By blocking muscarinic acetylcholine receptors, these chemicals hinder the activity of the parasympathetic system resulting in sedative and anesthetic effects. Application of these plant products directly to the penis and other genital areas, especially those with mucous membranes, leads to a general tingling and anesthetization of the area stemming premature ejaculation and increasing the duration of sexual activity.
Interestingly, the application of these drugs to the mucous membrane associated with the genital area has been repeated around the world. The Kama Sutra describes how an ointment of datura, pepper and honey allows a man to "make a woman subject to his will" (WWW 1). Medieval European witches applied an ointment of belladonna, mandrake and henbane to the moist membranes of the vagina using broomsticks and staffs as applicators. This ointment is what allowed witches to "fly on their broomsticks to their sabbaths" (Davis, 1985).
Another ancient aphrodisiac works through a similar mechanism. The aphrodisiac known as "love stone" in the West Indies and "chan su" in China, these chemicals have made a comeback in the 1990s in the United States under the names "Stone", "LoveStone", "Black Stone", "Stud 100" and "Rock Hard" (Brubacher et al. 1995). Love stone and chan su have been found to be nearly identical. They contain bufotenine and the bufadienolides resibufogenin, bufalin and cinobufagin derived from toads, especially Bufo bufo gargarizans, Bufo vulgaris and Bufo marinus (Barry et al. 1996; Davis 1985). Bufotenine is a tryptamine psychedelic related to psilocybin and bufadienolides are cardiotonic steroids, or steroids that disrupt the normal rhythm of the heart.
The recently marketed version of "Stone" came in a dry, brown-colored cube. When smoked, the effective delivery of bufotenine accentuates the hallucinogenic effect of the psychedelic. However, when ingested, the effect of the bufadienolides on the heart is accentuated. Between February of 1993 and May of 1995, four men died of cardiac dysrythmia after ingesting this marketed aphrodisiac. The packaging instructed consumers to moisten the cube and apply it externally to the penis to prolong erection. When used appropriately, this should produce an anesthetic effect. Once again, this anesthetic effect is intended to prolong the duration of an erection by numbing sensitivity.
One synthetic recreational drug often claimed as an aphrodisiac, has been employed in a similar way. Cocaine has been applied to the outside of the penis during intercourse. Cocaine interferes with voltage gated sodium channels, blocking action potentials and causing a local numbing sensation (Taberner 1985). The local anesthetic effect of cocaine leads to reduced sensitivity, again leading to increased duration of sexual activity.
The last physiologically active (but not psychoactive) drug to be examined is also used for the purpose of sustaining an erection. This time goal is not to desensitize the penis to avoid premature ejaculation, but to limit the influence of the sympathetic nervous system in order to correct erectile dysfunction, a disorder where men cannot maintain an erection. Erections come about and are maintained through activity in the parasympathetic nervous system. The sympathetic nervous system steps in either during ejaculation or when an erection fades. Viagra is a vastly successful, commercially available drug designed to treat erectile dysfunction.
Viagra actually derives its effectiveness from the fact that it suppresses the sympathetic nervous system in the corpi cavernosi, the spongy cavity in the penis that fills with blood during an erection. Viagra was synthesized by the biotechnology company Pfizer by accident while they were searching for a different sort of vasodilator. They stumbled upon a molecule that mimics the guanosine base of a cGMP that acts as a signaling molecule in a pathway that ultimately inhibits the sympathetic pathway very specifically in the tissues of the penis (WWW 2). Viagra, along with Spanish Fly, plant products containing scopolamine and atropine, bufotenine and the bufodienolides, and cocaine all elicit physiological responses in humans that some have deemed aphrodisiacal at some point in history.
The last major group of biologically active aphrodisiacs are those that are psychoactive in nature. This category is the most difficult to study because knowledge of both sexual arousal and the mechanisms of the psychoactive properties of drugs are limited. Only the most general information about sexual arousal and the brain is understood. Adrenergic, serotonergic and dopaminergic pathways have been the most carefully studied (Rosen and Ashton 1993).
Recently a great deal of attention has been placed on investigating the role of alpha-2 norepinephrine receptors in sexual arousal. This interest stemmed from the study of an alpha-2 adrenergic antagonist called yohimbine. Yohimbine is another historic aphrodisiac. Yohimbine is an alkaloid derived from the bark of the yohibehe tree from West Africa. It has been used as an aphrodisiac in Africa for centuries. In scientific literature it is also referred to as aphrodine or corynine. Yohimbine has been shown to be a powerful sexual stimulant in rats. However, similarly dramatic effects have yet to be found in humans. Originally, yohimbine was explored as a pure vasodilator which would treat erectile dysfunction vascularly. Alpha-2 adrenergic antagonists produce vasodilation by inhibiting normal vasoconstriction in the sympathetic nervous system, similar to the effect of Viagra. This could help initiation and maintenance of an erection. However, more recent studies have found that yohimbine's effects could modulate a more general psychological factor of sexual response, and thus have an indirect effect on erectile response (Rowland et al. 1997).
Serotonin has generally been viewed as an inhibitory transmitter in the control of sexual arousal. Selective serotonin reuptake inhibitors (SSRIs) increase the amount of time serotonin stays in the synaptic cleft. The primary side effect of these antidepressants is to decrease libido and make the achievement of an orgasm very difficult. More recently, the serotonergic antagonists LY53857 and LY281067 have been explored as potential prosexual drugs. Application of these compounds in rats has led to increase in sexual behavior and ejaculation in male rats(Rosen and Ashton 1993). However, the effects of MDA and MDMA, described as "speed for lovers", are described by users as incredibly aphrodisiacal despite the fact that the acute effects of these drugs are to increase the amount of serotonergic activity. This highlights the importance of the looking at the entire range of action of a drug. These drugs also produce a certain level of relaxation and euphoria to which these aphrodisiac effects could probably be attributed.
Dopaminergic stimulation of receptors during sexual response and arousal is located in the forebrain and midbrain regions. More specifically dopaminergic stimulation of the ventral area of the striatum seems to influence sex drive while the dorsal striatum region seems to control orgasm and ejaculation. Dopamine specific nerves span from the hypothalamus to the pituitary gland suppressing the release of prolactin. High levels of prolactin have been connected to lower libido (Rosen and Ashton 1993; Taberner 1985).
Dopamine antagonists like haloperidol appear to diminish sexual arousal while it has been argued that one of the precursors of dopamine, L-dopa has aphrodisiacal effects (Taberner 1985). When L-Dopa was first prescribed in the 1960s and 70s as a treatment for Parkinson's disease, there was a large number of clinical reports of hypersexuality in patients including eighty year old men returning to their youth with nocturnal emissions and erotic dreams. Some of this effect may have been attributable to the improved health and mood of the patients as a result of the drug's therapeutic effects. In 1970 an adult film chronicling a husband and wife's experience with the drug in graphic detail even bore the title L-Dopa. However, since then research on the effect of L-dopa on sexual arousal in humans has been mixed. It has been proposed that only some subgroup of patients have an increased susceptibility to the prosexual effects of L-Dopa, but this has not been investigated (Rosen and Ashton 1993).
On the opposite end of the spectrum, the observed response to a dopamine agonist, bromocriptine, has also supported the dopamine-prolactin model of sexual arousal. Bromocriptine increases the amount of dopamine reaching the anterior pituitary and consequently reduces the amount of prolactin in the body. It has been shown to increase the frequency of ejaculation, masturbation, intercourse and orgasm in a study of men suffering from sexual impotence (Taberner 1985).
The biological truth behind purported prosexual psychoactive drugs that affect the dopaminergic, serotonergic and adrenergic pathways in the brain are the most difficult to pin down. The current limited understanding of the complexity of the serves merely as a blunt tool for identifying aphrodisiacs. The data for this entire set of purportedly prosexual psychoactive compounds is limited to a collection of clinical studies that have great methodological difficulties. Every study seems to approach the quantification of increased sexual arousal in a different way. As a consequence of these factors, our knowledge of psychoactive prosexual drugs is limited. The body of knowledge on classical aphrodisiacs and drugs with physiological and nutritional effects is more complete. However, it is certain that our increasing understanding of the complexity of the brain and the increasing acceptance of sex related research in the scientific community will yield more information soon.