Current medical literature does not describe precisely the activation and mechanisms of prostate orgasms. This brief review describes what we know about the anatomy and physiology of the prostate and its involvement in reproduction and especially its stimulation for sexual recreation. It is illustrated with a highly relevant case history. Clin. Anat. 31:81–85, 2018. © 2017 Wiley Periodicals, Inc.

INTRODUCTION Gross Anatomy Cancer of the prostate is the most commonly diagnosed cancer in Western world males and is the second cause of cancer deaths in men (Siegel et al., 2015). The male human prostate is a musculoglandular organ the size of a walnut; it surrounds the neck of the bladder and urethra and is itself surrounded by a complex of fascial structures. Ayala et al. (1989) studied histologically whole organ sections of 50 prostate glands and concluded that a ‘capsule’ of the prostate does not exist, it being a concentrically placed fibromuscular band surrounding the prostate that is an inseparable component of the prostatic stroma. Raychaudhuri and Cahill (2008) in an extensive literature search about the pelvic fascia that included periprostatic structures confirmed this conclusion. However, Ali et al. (2004) still used the term ‘prostatic capsule’ when describing nerves passing through it into the prostate body. The gland can be divided into three zones, namely—a peripheral zone (75% of the gland, the portion that surrounds the distal urethra), a central zone (5–8% of the gland, the zone that surrounds the ejaculatory ducts), and a transitional zone (20% of the gland that surrounds the proximal urethra) all enclosed by the fibromuscular band.

DEVELOPMENT The complexity of the development of the prostate in humans from the embryonic urogenital sinus has been reviewed by Marker et al. (2003) and Santos and Taboga (2006). This embryonic structure is indistinguishable between male and female embryos until weeks 10–12 of gestation. It then differentiates under the influence of the androgens secreted initially by the fetal testes that maintain its embryonic and neonatal growth through activation of local paracrine factors (Thomson, 2001) finally creating male prostatic glandular activity at puberty (Isaacs, 1994).

GLANDULAR FUNCTIONS The functions of the prostate are its involvement in the reproductive aspects of the male ejaculate (its procreative function) and its involvement in the ecstacy of the orgasm (its recreative function). While there are many studies of its reproductive function(s) there are relatively few that characterize its recreative functioning. Most of the information about this pleasurable function comes from anecdotal sources. There is a website dedicated to its recreative function (see section below on prostate and the internet). It should be mentioned that there are suggestions that the gland also has a possible endocrine function. Kacker et al. (2014) reviewed the evidence that the gland contributed to the local and systemic concentrations of 5α‐dihydroxytestosterone, a more potent androgen than its precursor testosterone from which it is converted by the prostate expressed isoenzyme 5α‐reductase‐2 (Kang et al., 2014). The concentration of the androgen in the prostate is 5–10 times greater than that of testosterone (Hay and Wass, 2009). The importance of the prostate function for male fertility is exemplified by males who have a deficiency of this isoenzyme (5α‐reductase type 2 deficiency) as they have decreased sperm counts, low semen volume and failure of the semen to liquefy because of a deficiency of the prostate‐specific antigen (a serine protease) that de‐coagulates the gelled ejaculated semen.

NEURAL INNERVATION OF THE PROSTATE The gland is abundantly innervated by the parasympathetic (hypogastric and pelvic nerves) and by the sympathetic (hypogastric ganglion). According to Gupta and McVary (2017) ‘there is widespread agreement that expulsion of the contents of the gland during emission is under adrenergic control while cholinergic nerves are secretomotor’. In regard to the sensory innervation of the prostate, McVary et al. (1998) state that the majority of the afferents to the ventral prostate is localised to sensory nerves from the L5 and L 6 segments of the spinal cord but there is a smaller degree of innervation from T13 to L2. A collection of nerves that is located in the fascia covering the prostate is named the prostatic plexus. They arise from the lower (inferior) portion of the pelvic plexus and are distributed not only to the prostate but also to the corpora cavernosa of the penis and urethra. Injury or damage to these nerves impacts on the mechanisms of erection and can thus cause erectile dysfunction (see section below on orgasm and radical prostatectomy). Dense neuropeptide Y innervation is present throughout the prostatic stroma but most studies have not found the neuropeptide to be involved in the contraction of the prostate (White et al., 2013).

PROCREATIVE FUNCTIONS The serial order of the male ejaculate is composed of secretions from the glands of Littré (lining the penile urethra), Cowper's (bulbourethral) gland, testicular, and epididymal fluid containing the spermatozoa, the prostate and finally the seminal vesicles (Levin, 2005a). In this glandular company the prostate manufactures a highly complex secretion which becomes approximately 30% of the fluid volume of the ejaculate. It contains a large variety of constituents many having proposed or unknown function(s). These include citric acid (20–150 mM, function unknown), zinc [590 ± 45 SE µg/mL; Zaichick et al. (1996), possibly antibacterial], the enzyme prostatic specific antigen (PSA) that liquefies the coagulated semen after ejaculation, prostatic acid phosphatase, phosphorylcholine (specific substrate for previous enzyme), aminopeptidase, ATPase, spermine (Pegg, 2014) and spermidine (possible antibacterial activity, enzymatic breakdown gives semen its characteristic odor), prostasomes [small vesicles containing cholesterol, sphingomyelin, calcium, enzymes, and some 139 proteins—(Levin, 2005b)], lipids (Scott, 1945) and phospholipids of which sphingomyelin constitutes about half the latter with phosphatidyl serine and ethanolamine plasmalogen most of the remainder (their functions are unknown). Semen also contains some 60 plus peptides and proteins (Tsai et al., 1984; Fung et al., 2004). According to Baker and Bellis (1995) the prostate secretion provides the sperm with some protection from the seminal vesicle secretion that has spermicidal properties (Linderholmer, 1973).

THE PROSTATE AND EJACULATION The involvement of the prostate in the mechanisms of ejaculation was first promoted by Marberger (1974). He proposed that the distention of the prostatic urethra by the volume of the entering semen was the trigger for the initiation of the ejaculatory reflex and the theory was called ‘the prostatic pressure chamber trigger concept’. This speculative explanation was repeated by a number of authors (Jannini et al., 2002). Levin (2005a) reviewed the evidence for this mechanism and found that there were important experimental studies with results against the concept, namely that there are ‘definite occasions where the ejaculatory mechanisms is activated yet no seminal fluids enter the prostatic urethra’. Giuliano and Clement (2005), in their review of ejaculation, agreed that ‘the expulsion phase of ejaculation can occur in the absence of urethral stimulation and that the prostatic pressure chamber concept does not definitively identify the ejaculation trigger’.

RECREATIVE FUNCTIONS Descriptions of the Male Orgasms Unlike the female orgasm, where a number of competing descriptions for induced orgasms exist (see Levin, 2015), those for the male are limited (Zilbergeld, 1979; Otto, 1999). Surprisingly, neither Masters and Johnson (1966), Zilbergeld (1979), Margolis (2004), or Bancroft (2009) in their books on human sexual arousal mention those obtained from prostate stimulation in the male while even in the book on orgasm by Komisaruk et al. (2006) has only a single, very short paragraph of but two sentences. The classic penile‐induced male orgasm description is that of Masters and Johnson (1966) who characterized it into two separate stages. The first stage is initiated by the contractions of the various accessory organs beginning with the vasa efferentia of the testis, then the epididymis following through to the vas deferens with the contractions of the seminal vesicles. The prostatic contractions then occur. This stage is controlled by the thoracolumbar (T11‐L2) neural pathway (Giuliano and Clement, 2005). In this stage the male has a feeling of ‘ejaculatory inevitability’ and the knowledge that ejaculation is coming and cannot be delayed. The second stage is the seminal fluid flowing into the distended urethral bulb and the penile urethra. The perineal musculature (mainly the bulbocavernosus muscle, Levin, 2005) then propels the semen along the penile urethra to be expelled forcibly in spurts from the penile meatus, this is mediated by the sacral (S2‐S4) pathway (Giuliano and Clement, 2005). With each spurt a feeling of intense pleasure is generated which gradually subsides as the spurts decrease. Often nonverbal vocalizations occur with each spurt (Levin, 2006). If the pelvic muscles do not contract the semen emission is one of dribbling, powered by the peristaltic contractions of the urethra alone with little ecstatic pleasure (Newman et al., 1982). Although orgasm normally takes place concomitantly with ejaculation, the two processes are actually independent (Levin, 2003).While the prostate is involved in forming part of the ejaculate (as detailed above) it is also involved in ejaculation per se as its fibromuscular covering containing smooth muscle contracts clonically under its adrenergic innervation propelling the semen from the prostatic urethra into the penile urethra (White et al., 2013). Published descriptions of the prostate‐induced orgasm in academic and clinical literature have been thin on the ground (Levin, 2004). In an early article by Perry (1988) he described prostatic‐induced orgasms as ‘emission type reflexive orgasms’ with occasional oozing of semen from the penis. Such a description applies to ejaculations that occur when the pelvic striated muscles (especially the bulbocavernous) are nonfunctional (Newman et al., 1982). A paradox to note is that when induced ejaculations are without pelvic contractions they are of poor erotic value as previously described yet intense erotic pleasure appears to be activated by prostate stimulation even when there are no pelvic contractions to create semen ejaculation.

ORGASM AFTER RADICAL PROSTATECTOMY Men can experience changes in their sexual responses after radical prostatectomy, the gold‐standard treatment for localized cancer of the prostate. Early operations caused damage to the nerves that passed along the organ that subserved erection but later nerve sparing operations were designed to preserve this innervation. Koeman et al. (1994), for example, reported that in their series of prostatectomies (n = 20) no patient could maintain a rigid erection but 5 could manage to have coitus with their partial erection. None experienced the sensation of ‘ejaculatory inevitability’. A few (n = 7) complained that their orgasm was weakened and 9 had involuntary loss of urine at orgasm (climacturia). A very extensive, comprehensive, and up‐to‐date review of orgasmic dysfunctions after radical prostatectomy by Capogrosso et al. (2017) report that despite technical surgical advances ‘the achievement of good operative functional outcomes is still considered a troublesome issue both for patients and urologist’. These include impairments in sexual desire, penile morphology and orgasmic function. In relation to the latter the conditions of climacturia, orgasm associated pain and modification of orgasmic sensation are prevalent and even complete anorgasmia occurs. Unfortunately, reliable data from which to estimate these impairment risks are lacking.

THE ‘BRAIN REWIRING’ CONCEPT An obvious question is—why do prostate orgasms appear more powerful and pleasurable than penile induced ones? Increased body awareness has been linked to increased genital awareness and arousal in women (see Handy and Meston, 2016 for references). It is possible that similar heightened awareness occurs in those males who focus on and practice prostate stimulation. Such awareness could enhance the sexual pleasure obtained as modulation of physiological function can occur through changes in mental processes (Mitani et al., 2006). It is now accepted that the human brain is constantly changing its functional and structural properties depending on the variety of inputs and experiences. This plasticity is thought to be manifest through synaptic reorganization (Kolb et al., 2003) and/or the balance of excitation/inhibition among neurones (Cooke and Bliss, 2006). The brain literature refers to this as ‘the plasticity of the brain’ but in lay parlance a common description is ‘rewiring of the brain’ (Arden, 2010). Those learning to experience prostate‐induced orgasms often use this concept (see ‘prostate orgasms and the internet’ below).

PROSTATE ORGASMS AND THE INTERNET Because there have been no published laboratory‐conducted investigations of the orgasms induced by prostate stimulation alone, information about them has to be gathered from the various websites dedicated to such orgasms. While unsatisfactory in that the vast number are obviously anecdotal they represent the only available source. Unlike the sparsity of academic literature on prostate‐induced orgasms there appears to be an enormous number of internet sites involving such activity. Typing in ‘websites for prostate‐induced orgasms’ in Google produces 383,000 results (August, 2017). Specific products have been developed commercially to enable males to stimulate their prostates per rectum without using hands and these have created a large user community. One of the most popular is that devised by Aneros (http://www. Aneros.com) costing $69.95 while there is also a vibrating model (Vice) priced at $139.95. The Aneros Forum (https://www.com/community) is the commercially sponsored repository for individual's posts about their use of the various Aneros devices. Some of these listed posts have received hundreds of views while a few have over half a million. What many of these reports from individual users stress is that to obtain prostate‐induced orgasms needs relaxation, time and practice. Apart from the vibrating model, the device moves slightly associated with normal contraction of the internal and external anal sphincter, which is sufficient to stimulate the prostate and sensitive areas of the rectal wall. The subject can initiate these contractions, but once orgasm starts the device moves spontaneously in response to the orgasmic contractions, stimulating the prostate and increasing the intensity of the orgasm. Perry (1988) suggested that this area of the rectal wall was similar to the so‐called ‘G‐spot’ of the female in that it activated orgasm when stimulated so it has been called ‘the male G‐spot’, it is anatomically incorrect but a widely used description. Some get erections during its use while others do not. A number report extreme bouts of shaking/shuddering before the induced orgasms occur and when they do they are infinitely more pleasurable than those obtained from penile stimulation. One post included the interesting comment about the curse of the Aneros—‘it's addictive and it takes a good deal of time—at least 30 min’. The accepted term among the community of users for the very best orgasms induced by the stimulation is ‘Super‐O's’ which everyone strives to obtain (see ‘Relevant Case Study’ below).

THE RELEVANT CASE STUDY The subject was a 63‐year‐old, medically qualified male in good physical health with a good libido and a normal prostate on digital examination. He experimented initially with an Aneros helix prostate stimulator for prostatic massage to relieve symptoms from an episode of prostatitis. He rapidly became highly orgasmic with the device (without the use of sexual fantasy) after only a few hours of use, spread over several occasions. He also had a course of the PDE‐5 inhibitor tadalafil 2.5 mg daily which is now licensed for lower urinary tract symptoms in men. His prostatitis symptoms resolved within 2 months of regular Aneros use several times weekly combined with tadalafil. However, he found that the intense orgasms produced by the device were highly addictive and many were subjectively in the ‘Super‐O’ category described above. Despite the device being inserted in the anus and lower rectum, he described the orgasms as being felt in the penis, perineum, and pelvis, similar to a normal male orgasm. When becoming really intense in the Super‐O category, he experienced some whole body sensation with some involuntary muscular contracting and shaking. He stopped using the Aneros after about 2 months and attempted to overcome the addiction to the device. Whilst using the Aneros, he had produced some secretions from the urethra, but he did not normally ejaculate. He had been in the habit of wearing a condom to catch these secretions and any possible ejaculate. He had mainly used the device lying prone with a couple of pillows to support his pelvis with the penis hanging comfortably in between, as he would some of the time become erect or partially erect whilst using the device. The Aneros forum describes a process of rewiring when learning to orgasm with the device and it then becomes possible to experience Aneros‐free orgasms. Our subject found that he could achieve intense orgasms by lying prone wearing a condom without the Aneros present, the condom and the pillows being sufficient stimuli to trigger a reflex orgasm without any direct mechanical stimulation to the penis. The ability to orgasm without the device has persisted for at least 12 months since the last insertion of the Aneros. This subject found that whilst the orgasms were extremely enjoyable at the time, he could easily spend too much time experiencing them. Further, he had an old neck injury which flared up in association with some neck spasm at orgasm whilst lying prone. It has proved difficult to stop experiencing these orgasms and ‘unwire’ himself back to normal. He attempted this by replacing the passive stimulus with stimulatory masturbation or sexual intercourse, and in the process became multiorgasmic with both sexual scenarios up to 10 orgasms before the final ejaculation). He has managed to stay off non‐stimulatory orgasms for several months at a time, but has had a tendency to relapse.

CONCLUSIONS Despite the fact that so much of the information that is available about prostate‐induced orgasms comes from the anecdotal reports of individuals, there can be little doubt that stimulating the prostate via the rectal wall can create ecstatic feelings that are exceptionally pleasurable, often surpassing those obtained from penile stimulation. However, the exact mechanism(s) by which these are induced is unclear, some propose it is by the nerves passing along the outer surface of the gland (prostatic plexus), others suggest it is via the nervous innervation of the prostate itself while others talk about a ‘re‐wiring’ of the brain needed to appreciate the effects of the organ's stimulation. What is clear, however, is the reticence of the scientific community to study the phenomenon possibly because it involves the need for rectal insertion and stimulation. Why, for an obvious example, have we still not had any brain imaging of prostate‐stimulated orgasms so that we can compare them with penile orgasms? Who will lead the challenge?

ACKNOWLEDGMENTS I would like to thank the anonymous subject, Dr. A, for bringing to my attention this grossly under researched area of prostate function.

CONFLICT OF INTEREST The author has no conflicts of interest to declare.