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brain scansWhat Do the Scientists Have to Say?

A surprising amount of research - much of it quite recent - suggests that sex has lingering effects on the brain, and that climax has much in common with drugs. In short, the effects are quite likely powerful enough to affect our perceptions, priorities, feelings of wellbeing, contentment and relationship harmony for a time. Indirectly, this research also suggests why karezza may naturally increase our capacity to bond, and help counter addiction, stress and depression. Funding sources and long held assumptions, however, ensure that most researchers in the area are engaged in the study of how pharmaceuticals might be developed to "enhance" conventional sex forcefully (and sometimes clumsily), rather than the study of how we might work with our biology to protect our pair bonds and enhance our overall wellbeing.

James G. Pfaus, PhD

Ejaculation in men induces a refractory period.  This period can vary from minutes to hours to even days.  Unfortunately very little is known about it other than what has been studied (and perhaps modeled) in rats.  It is a period of inhibition...  over erection, over further ejaculation if erection is obtainable, and most surely over desire and subjective arousal.  Neurochemically, it is characterized by activation of opioid, serotonin, and possibly endocannabinoid systems (along with many others like prolactin and oxytocin) that essentially depress hypothalamic systems that regulate desire and autonomic blood flow, along with limbic structures that regulate desire and specific sexual motivation.  It can induce sleep.  It results in long-term decreases in resting heart rate that can last well over 12 hrs after a single ejaculation.  Of course, in men with PE, ejaculation can induce an aversive state, as can ejaculation in men that suffer headaches afterward.  That said, what can alter this?

The neurochemical systems for arousal and desire (e.g., dopamine, noradrenaline, melanocortin, oxytocin, vasopressin, et al.).  Heightening of these, either pharmacologically or by stimuli that drive them (e.g., porn, pain, games, bondage, increasingly arousing fetish ideation, threat, or visual stimulation, etc.) can reduce the intensity of the inhibition -- for a while, and perhaps long enough to obtain another erection.  In men for whom such inhibition is diminished in the first place (in those with frontal damage, e.g., Kluver-Bucy, or in men that have a largely dopamine driven OCDs), it is possible that they gravitate toward what in their minds are highly arousing stimuli. If they are also ADD, then it is possible that they fail to focus on one and only one stimulus for a very long time.  The ease with which they can download multiple images or stream different videos would certainly play into this scheme as an "easy" way to charge the arousal and desire systems. 

Here's a selection of research we think is relevant.

Orgasm Cycle. A brief list of some of our articles is followed by a long list of relevant research. As a recent American Society of Addiction Medicine statement explained,

When one engages non-pathologically in potentially addictive behaviors such as gambling or eating [or sex], one may experience a "high", felt as a "positive" emotional state associated with increased dopamine and opioid peptide activity in reward circuits. After such an experience, there is a neurochemical rebound, in which the reward function does not simply revert to baseline, but often drops below the original levels. This is usually not consciously perceptible by the individual and is not necessarily associated with functional impairments.

Why Stop Orgasm Research at Climax? (Huffington Post)

Orgasm's Hidden Cycle

Men: Does Frequent Ejaculation Cause A Hangover?

Women: Does Orgasm Give You A Hangover?

Will Orgasms Keep You in Love?

What is "the chaser?"

Studies pointing to a neurochemical cycle after climax

In order to make sense of the findings below, the reader must first understand the critical importance of dopamine. Dopamine is associated with motivation and salience. It powerfully influences or mood, perception and priorities – and if it’s too high or too low, we can feel a bit manic, or the reverse. Many of the post-climax neurochemical events listed below have an impact on dopamine among their effects on limbic tone. These subtle, but very real, brain changes occur without conscious awareness. Often they can only be observed clearly over time, when we contrast how we feel when engaged in excessive stimulation with how we feel when engaged in practices that improve limbic tone, such as meditation, exercise, prudent management of sexual impulses, healthy diet, etc. More items on dopamine’s critical impact below.

General

  • The human sexual response cycle: brain imaging evidence linking sex to other pleasures (2012) The functional neuroanatomy of sexual behavior is comparable to that involved in processing other rewarding stimuli. Sexual behavior clearly follows the established principles and phases for wanting, liking and satiety involved in the pleasure cycle of other rewards. The studies have uncovered the brain networks involved in sexual wanting or motivation/anticipation, as well as sexual liking or arousal/consummation, while there is very little data on sexual satiety or post-orgasmic refractory period…. it is unlikely that there is anything special about the brain mechanisms and networks underlying sex.
  • Exposing orgasm in the brain: a critical eye (2012) Georgiadis critically reviews the available evidence on orgasm and the human brain.
  • Male Sexual Behavior (Chapter, Dec, 2009) Major areas controlling sexual motivation and performance in males include the mesolimbic dopamine (DA) system, the medial preoptic area (MPOA), the amygdala, and the bed nucleus of the stria terminalis (BST). Genital reflexes are controlled by the MPOA, paraventricular nucleus (PVN), brainstem, and spinal cord areas. Mating is integrated by the MPOA, amygdala, BST, PVN, and mesolimbic and nigrostriatal tracts, which are also important for other social behaviors.
  • Influences of dopamine and glutamate in the medial preoptic area on male sexual behavior.(2014) Neurochemical studies have demonstrated that both dopamine and glutamate levels rise in the mPOA in response to sexual activity, while antagonism of these neurotransmitters impairs male sexual response….Here we review how dopamine and glutamate act in the mPOA to modulate male sexual behavior.

Post-climax effects - general

  • Recovery from sexual exhaustion-induced copulatory inhibition and drug hypersensitivity follow a same time course: two expressions of a same process? (2010) Comment: Sexual exhaustion in rats is marked by multiple brain changes that take at least 4 days to reverse. At the same time, full recovery of sexual activity (number of copulations and ejaculations) takes 15 days. This researcher believes, as we do, that sexual satiation is a mechanism to prevent over-stimulation of the reward circuitry. From study: It could be thought that the long lasting sexual inhibition resulting from copulation to satiation constitutes a protective mechanism against over stimulation of the brain circuits involved in its processing. The mesolimbic system plays a role in the processing of natural rewards including sexual behaviour [2]. Constant stimulation of this circuit by repeated administration of drugs of abuse produces behavioural sensitisation [16] that resembles the drug hypersensitivity exhibited by sexually exhausted rats after repeated ejaculation in a short period, which would continually stimulate the mesolimbic system.
  • Pharmacological and physiological aspects of sexual exhaustion in male rats (2003) Comment: Drastic reduction in androgen receptor density in specific regions of the brain (MPOA) following sexual activity. May take up to 7 days to recover from sexual activity, perhaps due to androgen receptor decrease after orgasm for 4-7 days, which decreases effects of testosterone. The present article reviews the current findings on the interesting phenomenon of sexual satiety. Knut Larsson in 1956 reported on the development of sexual exhaustion in the male rat after repeated copulation. We have studied the process and found the following results.
    • (1) One day after 4 hours of ad libitum copulation, two-thirds of the population showed complete inhibition of sexual behavior, while the other third displayed a single ejaculatory series from which they did not recover.
    • (2) Several pharmacological treatments, including 8-OH-DPAT, yohimbine, naloxone and naltrexone, reverse this sexual satiety, indicating that the noradrenergic, serotonergic and opiate systems are involved in this process. Indeed, direct neurochemical determinations showed changes in various neurotransmitters during sexual exhaustion.
    •  (3) Given enough stimulation, by changing the stimulus female, sexual satiety was prevented, suggesting that there are motivational components of the sexual inhibition that characterizes sexual exhaustion. [Coolidge]
    •  (4) The GABA antagonist bicuculline, or the electrical stimulation of the medial preoptic area, did not reverse sexual exhaustion. These data suggest, on the one hand, that sexual exhaustion and the postejaculatory interval (which is shortened by bicuculline administration) are not mediated by similar mechanisms and, on the other, that the medial preoptic area does not regulate sexual satiety.
    • (5) The androgen receptor density in brain areas closely related to the expression of masculine sexual behavior, such as the medial preoptic nucleus, was drastically reduced in sexually exhausted animals. Such reduction was specific to certain brain areas and was not related to changes in the levels of androgens. These results suggest that changes in brain androgen receptors account for the inhibition of sexual behavior present during sexual exhaustion.
    • ( 6 ) The recovery process of sexual satiety after 4 hours of ad libitum copulation reveals that, after 4 days, only 63% of the males are able to show sexual behavior while after 7 days all animals display copulatory activity.
  • Revisiting post-ejaculation refractory time-what we know and what we do not know in males and in females (2009) [Review] Despite numerous studies in rats the mechanisms and site(s) of the activity are poorly understood. Dopaminergic and adrenergic pathways are thought to shorten PERT whereas serotonergic pathways lengthen its duration. Raising the brain serotonin levels in men using SSRIs helps reduce early or premature ejaculation. Rats have an absolute PERT (aPERT) during which erection and ejaculation is inhibited and a relative PERT (rPERT) when a stronger or novel stimulus can, whether such phases exist in men is unexamined. Apart from possible depressed activity in the amygdala and penile dorsal nerve and rejection of prolactin as a major factor in PERT little or no significant advance in understanding human male PERT has occurred.
  • c-Fos expression related to sexual satiety in the male rat forebrain (2007) [c-Fos is a transcription factor, and way to measure neuronal activity, nerve impulses] The long term inhibition of masculine sexual behavior after repeated ejaculations is known as sexual satiety. To investigate the brain areas that may regulate sexual satiety, c-Fos expression was studied in different groups of sexually experienced male rats: controls not allowed to copulate, males allowed two or four ejaculations and animals allowed to reach sexual satiety. Interestingly, males that ejaculated two or four times had similar c-Fos densities in all the evaluated brain regions, except for the suprachiasmatic nucleus. Similarly, sexually satiated males had analogous c-Fos densities in all the evaluated brain areas independently of the number of ejaculations required to reach satiety. …These results suggest that the network that underlies sexual satiety is different from that which regulates copulation.
  • Electrical stimulation of dorsal and ventral striatum differentially alters the copulatory behavior of male rats (2010) Electrical stimulation of the NAcc at both frequencies increased the number of ejaculations that male rats were able to show in a 30-min period. By contrast, stimulation delivered to the CP inhibited sexual behavior by slowing its display. Each effect was more pronounced at low than at high stimulation frequencies. In the same rats, once sexually exhausted, electrical stimulation of these brain areas did not reverse the sexual behavior inhibition that characterizes the sexual exhaustion state.
  • Brain areas activated after ejaculation in healthy young human subjects (2007) Using Blood Oxygen Level Dependent (BOLD) functional magnetic resonance imaging (fMRI) we have mapped brain areas in healthy young volunteers immediately after ejaculation. Functional imaging of the brain for 30 minutes beginning after three minutes of ejaculation induced by masturbation showed spatio-temporal activation in amygdala, temporal lobes and septal areas. The septal areas were observed to be active for a shorter duration than the amygdala and the temporal lobe.
  • Neural activation following sexual behavior in the male and female rat brain (1998) Neural activation following sexual behavior was studied in the male and female rat brain, using Fos-immunoreactivity (Fos-IR) as a measure….Within the larger brain structures involved in sexual and other social activities, a specific ejaculation-related subcircuit exists, which may, under normal conditions in the rat, serve a 'sexual-satiety function'.

Post-climax effects - Androgen receptors and serum testosterone

  • Sexual Behavior Reduces Hypothalamic Androgen Receptor Immunoreactivity (2003) Neurons in these brain areas are rich in ANDROGEN RECEPTORS (AR) and express FOS-immunoreactivity in response to mating. In many species sexual satiation, a state of sexual behavior inhibition, is attained after multiple ejaculations. The mechanisms underlying sexual satiation are largely unknown. In this study we show that sexual activity reduces androgen receptor immunoreactivity (ANDROGEN RECEPTORS –ir) in some of the brain areas associated with the control of male sexual behavior, but not in others. Thus, one ejaculation reduced the AR-ir in the MPN and nAcc, but not in the BST and VMN. Copulation to satiation, on the other hand, reduced AR-ir in the MPN, nAcc and VMN, and not in the BST. The AR-ir reduction observed in the MPN of sexually satiated rats was drastic when compared to that of animals ejaculating once. Serum androgen levels did not vary after one ejaculation or copulation to exhaustion. These data reveal that sexual activity reduces ANDROGEN RECEPTORS in specific brain areas and suggest the possibility that such a reduction underlies the sexual inhibition that characterizes sexual satiety.
  • Relationship Between Sexual Satiety and Brain Androgen Receptors (2007) Comment: Reduction in sexual activity in sexually-satiated rats was accompanied by reduction in androgen receptors. “48 h after sexual satiety 30% of the males displayed a single ejaculation and the remaining 70% showed a complete inhibition of sexual behavior.” Comment: 72 hours later, androgen receptors had returned to normal. Testosterone levels did not change during recovery. As full sexual potency takes 15 days to fully return in rats, other factors must be involved in sexual inhibition of sexual behavior for 15 days.
  • Relationship between sexual satiety and motivation, brain androgen receptors and testosterone in male mandarin voles (2013) Androgen receptors participate in the neuroendocrine regulation of male sexual behavior, primarily in brain areas located in the limbic system. Males of many species present a long-term inhibition of sexual behavior after several ejaculations, known as sexual satiety. It has been shown in rats that androgen receptor expression is reduced 24h after a single ejaculation, or mating to satiety, in the medial preoptic area, nucleus accumbens and ventromedial hypothalamus. …Sexual satiety was associated with decreased AR and T expression in the lateral septal nucleus (LS), medial amygdala (MeA), medial preoptic area (mPOA) and ventromedial hypothalamic nucleus (VMH). Comment: However, serum testosterone levels remained unchanged after 24 hours, in both males who mated to satiety and males who were exposed to receptive females but prevented from mating. There is a relationship between sexual activity and a decrease in AR and T expression in specific brain areas.
  • Changes in the sexual behavior and testosterone levels of male rats in response to daily interactions with estrus females (2014) Following the initial peak, testosterone concentrations fluctuated less in males exposed to females than in controls. Sexual activity was not found to predict testosterone concentration. We conclude that when male rats have daily sexual interactions, sexual behavior tends to show cyclic changes and testosterone is significantly elevated only on the first day of interactions. Comment: When male rats have daily sexual interactions, sexual behavior tends to show 4-day cyclic changes.
  • Anabolic androgens restore mating after sexual satiety in male rats (2007) Comment: Long-term inhibition of masculine mating behavior after repeated ejaculations is associated with changes in both androgen receptor and estrogen receptor-alpha expression.
  • A research on the relationship between ejaculation and serum testosterone level in men (2003) Fluctuations of testosterone levels from the 2nd to 5th day of abstinence were minimal. On the 7th day of abstinence, however, a clear peak of serum testosterone appeared, reaching 145.7% of the baseline ( P < 0.01). No regular fluctuation was observed following continuous abstinence after the peak.
  • Hormonal responses to different sexually related conditions in male rats (2006) Comment: Testosterone rises after copulation in rats, but within 24 hours it's back to normal.
  • Testosterone restoration of copulatory behavior correlates with medial preoptic dopamine release in castrated male rats (2001) A consistent relationship between MPOA DA release during exposure to a receptive female and the subsequent ability of the male to copulate was observed. Comment: Sexual activity reduces androgen receptors in specific brain areas, and androgens regulate sexual desire through activating reward circuitry dopamine levels.
  • Effects of testosterone metabolites on copulation and medial preoptic dopamine release in castrated male rats (2003) Comment: Testosterone acts through reward circuit dopamine to affect sexual desire.
  • Circulating neuroactive c21- and c19-steroids in young men before and after ejaculation (2006) Twelve neuroactive and neuroprotective steroids, androgens and androgen precursors …were measured using the GC-MS system in young men before and after ejaculation provoked by masturbation. The circulating level of 17alpha-hydroxypregnenolone increased significantly, whereas the other circulating steroids were not changed at all. This fact speaks against the hypothesis that a drop in the level of neuroactive steroids, e.g. allopregnanolone may trigger the orgasm-related increase of oxytocin, reported by other authors. Comment: Level of 17alpha-hydroxypregnenolone increased significantly, whereas the other circulating steroids - including DHEA - were not changed at all.

Post-climax effects - Glutamate

Post-climax effects - Opioids

Post-climax effects – Prolactin

  • The post-orgasmic prolactin increase following intercourse is greater than following masturbation and suggests greater satiety (2006) Prolactin increases following orgasm are involved in a feedback loop that serves to decrease arousal through inhibitory central dopaminergic and probably peripheral processes….the magnitude of prolactin increase following intercourse is 400% greater than that following masturbation.
  • NMDA-Mediated Activation of the Medial Amygdala Initiates a Downstream Neuroendocrine Memory Responsible for Pseudopregnancy in the Female Rat (2001) Nocturnal and diurnal PRL surges are expressed repeatedly for up to 2 weeks after copulation, suggesting that a neuroendocrine memory for vaginocervical stimulation (VCS) is established at the time of mating. Comment: Prolactin surges continue for 2 weeks after female rats mate, even if no pregnancy occurs.
  • Prolactin release after mating and genitosensory stimulation in females (1995) Females exposed to intromissive stimuli from males show responses that are not shown by females receiving the same flank and perineal somatosensory input from mounts-without-intromission or the olfactory input from nonmating exposure to males. Comment: Sufficiently vigorous intromissions [repeated and intermittent] induce 10-13 days of twice-daily prolactin surges.
  • Coitus-induced orgasm stimulates prolactin secretion in healthy subjects (2001) These data [on partnered sex], together with previous evidence that masturbation-induced orgasm produces pronounced, long-lasting increases in plasma prolactin concentrations in both males and females, suggest a role for acute prolactin alterations in modifying human sexual desire following orgasm.
  • Prolactin secretory rhythm of mated rats induced by a single injection of oxytocin (2006) Comment: Oxytocin surge at orgasm may cause post-orgasmic prolactin. Complete study
  • A mathematical model for the mating-induced prolactin rhythm of female rats (2006) Comment: Injection of oxytocin sets off prolactin rhythm in female rats.
  • Prolactin secretory rhythm in women: immediate and long-term alterations after sexual contact (2012) Compared with control condition, sexual intercourse with orgasm induced not only the well-established immediate PRL increase of ~300% but also an additional PRL elevation around noon of the next day (P< 0.05). These fluctuations were measured on top of the regular circadian rhythm of PRL, manifested as a surge early in the morning.
  • Neuroendocrine response to film-induced sexual arousal in men and women (2000) Subjective sexual arousal increased significantly in both men and women during the erotic film, with sexual arousal eliciting an increase in blood pressure in both males and females, and plasma noradrenaline in females only. In contrast, adrenaline, cortisol and prolactin levels were unaffected by sexual arousal. These data further consolidate the role of sympathetic activation in sexual arousal processes. Furthermore, they demonstrate that increases in plasma prolactin during sexual stimulation are orgasm-dependent, suggesting that prolactin may regulate a negative-feedback sexual-satiation mechanism.
  • (Lay) Men's Sexual Problems Linked to Low Prolactin Levels (2013) Sexual problems in men may be linked to low levels of the hormone prolactin.
  • Prolactin secretion patterns: basic mechanisms and clinical implications for reproduction (2010) [Review] Data point to the important role of oxytocin as a crucial PRL-releasing factor. Recent data on human studies and their theoretical and clinical implications are reviewed as well. In particular, studies demonstrating a sustained PRL surge after sexual climax in males and females are presented, indicating possible implications for both sexual satiation and reproductive functions. Taking these data together, there is evidence for the hypothesis that the PRL surge induced by sexual activity, together with the altered PRL rhythmic pattern, is important for successful initialization of pregnancy not only in rodents but also possibly in humans.
  • Specificity of the neuroendocrine response to orgasm during sexual arousal in men (2003) Sexual activity induced transient increases of plasma epinephrine and norepinephrine levels during orgasm with a rapid decline thereafter. In contrast, prolactin levels increased immediately after orgasm and remained elevated throughout the experiment. Although oxytocin was acutely increased after orgasm, these changes were not consistent and did not reach statistical significance. Vasopressin, LH, FSH and testosterone plasma concentrations remained unaltered during sexual arousal and orgasm. These data confirm that prolactin is secreted after orgasm and, compared with oxytocin, seems to represent a more reliable and sustained marker for orgasm in man.
  • Orgasm-induced prolactin secretion: feedback control of sexual drive? (2002) Plasma prolactin (PRL) concentrations are substantially increased for over 1h following orgasm (masturbation and coitus conditions) in both men and women, but unchanged following sexual arousal without orgasm….Chronic elevations of PRL (hyperprolactinemia) produce pronounced reductions in animal sexual activity, and significant reduction of libido and gonadal function in both men and women.
  • Absence of orgasm-induced prolactin secretion in a healthy multi-orgasmic male subject (2002) We investigated the prolactin response of a healthy multi-orgasmic male subject. The prolactin response of the case-subject was compared with that of nine healthy adult men with a normal refractory period. The case-subject showed no prolactin response to three orgasms. Data from this multi-orgasmic subject support the hypothesized role of plasma prolactin in contributing to sexual-satiation mechanisms.
  • Prolactinergic and dopaminergic mechanisms underlying sexual arousal and orgasm in humans (2005) Here, we provide a brief overview of the physiology of dopamine and prolactin in regulating sexual behavior….dopamine agonists have facilitatory properties for penile erection but may also enhance sexual drive and orgasmic quality. In contrast, chronic elevations of prolactin inhibit appetitive as well as consummatory parameters of sexual behavior. Recent human studies show a marked increase in prolactin after orgasm in males and females. Concerning the biological relevance of acute prolactin alterations after orgasm, prolactin might serve as a neuroendocrine reproductive reflex for peripheral reproductive organs. Alternatively, prolactin may feedback to dopaminergic neurons in the central nervous system and thereby modulate sexual drive and satiation.
  • Effects of acute prolactin manipulation on sexual drive and function in males (2003) Administration of cabergoline decreased prolactin levels and significantly enhanced all parameters of sexual drive (P<0.05), function (P<0.01) and positive perception of the refractory period (P<0.01). Administration of protirelin increased prolactin concentrations and produced small, but not significant reductions of sexual parameters. The sexual effects observed from cabergoline were completely abrogated by coadministration of protirelin. …These data demonstrate that acute changes in prolactin plasma levels may be one factor modulating sexual drive and function. Therefore, besides a neuroendocrine reproductive reflex, a post-orgasmic prolactin increase may represent one factor modulating central nervous system centers controlling sexual drive and behavior. These findings may offer a new pharmacological approach for the treatment of sexual disorders.
  • “Prolactin: An integral player in hormonal politics” By Jeremy P.W. Heaton, MD Contemporary Urology, v.15:17-25 (2003)
  • Ecstasy (MDMA) mimics the post-orgasmic state: Impairment of sexual drive and function during acute MDMA-effects may be due to increased prolactin secretion (2005) The phenomenological features of the psychological state induced by MDMA show some similarities with features of the post-orgasmic state. In addition, MDMA also induces a prominent increase of prolactin plasma levels with a similar time kinetic compared to the post-orgasmic prolactin increase. Here, we present the hypothesis that the impairment of sexual parameters after MDMA may be mediated by increased prolactin.

Post-climax effects – Serotonin

Oxytocin - Functions

  • Relationships among cardiovascular, muscular, and oxytocin responses during human sexual activity. (1994) Comment: Plasma oxytocin shoots up and drops within minutes at masturbation-induced orgasm. Levels not linked to intensity...except in multi-orgasmic women.
  • Plasma oxytocin increases in the human sexual response. (1987) Plasma OT levels increased during sexual arousal in both women and men and were significantly higher during orgasm/ejaculation than during prior baseline testing. We suggest that the temporal pattern of secretion could be related to smooth muscle contractions of the reproductive system during orgasm.
  • Centrally released oxytocin mediates mating-induced anxiolysis in male rats (2007) Sexual activity and mating are accompanied by a high level of arousal, whereas anecdotal and experimental evidence demonstrate that sedation and calmness are common phenomena in the postcoital period in humans. These remarkable behavioral consequences of sexual activity contribute to a general feeling of well being, but underlying neurobiological mechanisms are largely unknown. Here, we demonstrate that sexual activity and mating with a receptive female reduce the level of anxiety and increase risk-taking behavior in male rats for several hours. … In the present study, we reveal that oxytocin is released within the brain, specifically within the hypothalamic paraventricular nucleus, of male rats during mating with a receptive female. Furthermore, blockade of the activated brain oxytocin system by central administration of an oxytocin receptor antagonist immediately after mating prevents the anxiolytic effect of mating, while having no effect in nonmated males.
  • Oxytocin receptor is expressed in the penis and mediates an estrogen-dependent smooth muscle contractility (2004) OT receptor is expressed in the penis at a concentration similar to that present in other portions of the male genital tract and mediates CC contractility. …As we found that CC [corpus cavernosum] expresses both subtypes of estrogen receptors and P450 aromatase, we hypothesized a physiological role for endogenous estrogens in regulating OT responsiveness….OT might participate in inducing postorgasmic penile flaccidity and suggest a new role for estrogens in the male: regulation of CC responsiveness to OT.
  • Oxytocin Mediates the Estrogen-Dependent Contractile Activity of Endothelin-1 in Human and Rabbit Epididymis (2005) Comment: Oxytocin plays a role in spontaneous motility necessary for sperm transport.

Dopamine - arousal

Arousal (non-dopamine)

  • The endocrinology of sexual arousal (Bancroft, 2005) The relevance of testosterone, oestradiol and certain peptides (oxytocin (OT), β-endorphin and prolactin (PRL)) to sexual arousal in humans is reviewed. Comment: Mentions 15-day recovery in sexually-satiated male rats.
  • Sexual Behavior and Sex-Associated Environmental Cues Activate the Mesolimbic System in Male Rats (2004) The mesolimbic system plays an important role in the regulation of both pathological behaviors such as drug addiction and normal motivated behaviors such as sexual behavior….Significant increases in MOR [opioid receptor] internalization were observed following copulation or exposure to sex-related environmental cues….Significant increases in the percentage of activated dopaminergic neurons were observed following copulation or exposure to sex-related environmental cues. In addition, mating and sex-related cues activated a large population of nondopaminergic neurons in VTA as well as neurons in both the NAc Core and Shell.
  • A new role for GABAergic transmission in the control of male rat sexual behavior expression (2016) GABAA receptors differentially regulate copulation depending on the sexual condition. Systemic bicuculline reverses sexual satiety, but lacks an effect in sexually active male rats. Intra-VTA bicuculline induces copulation in sexually satiated male rats. GABA controls male rat sexual behavior responding at the VTA.

Dopamine-related mood, bonding effects, priorities

Dopamine: a common thread? Although symptoms such as erectile dysfunction, social anxiety, lack of motivation, concentration problems and depression are quite different, they share a common finding in the scientific literature. All have been associated with altered dopamine signaling in the brain’s reward circuitry. Dopamine is the “go get it” neurochemical essential for libido, risk-taking, motivation, focus, and anticipation and cheerfulness. Thus, a decline in dopamine signaling is associated with all of these:

In contrast, when dopamine and related neurochemicals are properly regulated, sexual attraction, socializing, concentration, feelings of wellbeing and sound judgment are more effortless. We suspect that a return to normal dopamine signaling helps explain why many guys report the same improvements as they unhook from excessive consumption of Internet porn. The reports are often striking.

Here’s a sampling of interesting research that helps elucidate the vulnerability of the reward system, which “runs on” dopamine signals to a large extent:

Women (only) – perception changes after sex

  • Postcoital Dysphoria: Prevalence and Psychological Correlates (2015) Forty‐six percent of respondents reported experiencing PCD [postcoital dysphoria] symptoms at least once in their lifetime with 5.1% experiencing PCD symptoms a few times within the past 4 weeks…. attachment and differentiation of self variables did not account for significant variance. There appears to be no relationship between PCD and intimacy in close relationships.
  • Psychological Symptoms in a UK Population Sample of Female Twins (2011) Postcoital psychological symptoms (PPS) is a virtually unexplored phenomenon in the female population even though women frequently complain about irritability and motiveless crying after intercourse and/or orgasm. …3.7% of women reported suffering from recent PPS and 7.7% from persistent PPS….VCA [variance component analysis] revealed that phenotypic variance was best explained by an additive genetic (AE) model, ascribing 28% (for recent PPS) and 26% (for persistent PPS) of phenotypic variance to additive genetic effects, with the rest being a result of individual experiences and random measurement error.
  • The Prevalence and Correlates of Postcoital Dysphoria in Women (2011) Among 222 female university students, 32.9% reported having ever experienced PCD whereas 10% reported experiencing PCD in the previous 4 weeks….These factors [psychological distress and childhood sexual abuse] explained only minimal variance in PCD prevalence, prompting further research into this significantly underinvestigated sexual difficulty.
  • Sexual activity is inversely related to women’s perceptions of the facial attractiveness of unknown men (2007) Forty-five women reported the frequency of a variety of sexual behaviors and rated the facial attractiveness and friendliness of 24 men. Women who reported more frequent orgasm from masturbation rated men as less friendly. This finding might be reflective of the more anti-social attitude associated with more frequent masturbation. The results also show that women who engaged more frequently in most kinds of sexual behavior, not only PVI, considered unknown men to be less facially attractive. That is, individuals who engage more frequently in a variety of sexual behaviors with their partner perceived unknown men as less attractive and thereby may be less susceptible to the lure of other (or if the only sexual behavior is masturbation, any) men.

Sexual learning and brain plasticity

Mechanisms common to sexual experience and drug use

Sexual experience, behavioral addictions and drug addictions share common mechanisms and result in similar brain changes. Recent research is starting to reveal some of this overlap.

Implications for pair-bonding mammals