
What 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)
Men: Does Frequent Ejaculation Cause A Hangover?
Women: Does Orgasm Give You A Hangover?
Will Orgasms Keep You in Love?
Studies pointing to a neurochemical cycle after climax
- Different amounts of ejaculatory activity, a natural rewarding behavior, induce differential mu and delta opioid receptor internalization in the rat's ventral tegmental area (2013)
- Opioid receptor and β-arrestin2 densities and distribution change after sexual experience in the ventral tegmental area of male rats (2018)
- Influences of social reward experience on behavioral responses to drugs of abuse: Review of shared and divergent neural plasticity mechanisms for sexual reward and drugs of abuse (2017)
- Dopamine and opioid systems interact within the nucleus accumbens to maintain monogamous pair bonds (2016)
- The Role of FosB in the Medial Preoptic Area: Differential Effects of Mating and Cocaine History (2016)
- A new role for GABAergic transmission in the control of male rat sexual behavior expression (2016)
- Male Sexual Behavior (Chapter, Dec, 2009)
- Fruit fly sex drive hints at how animals choose behaviors AND "Dopaminergic Circuitry Underlying Mating Drive" (2016)
- Colocalization of Mating-Induced Fos and D2-Like Dopamine Receptors in the Medial Preoptic Area: Influence of Sexual Experience (2016)
- Sexual experience influences mating-induced activity in nitric oxide synthase-containing neurons in the medial preoptic area. (2014)
- Astrocytes in the medial preoptic area modulate ejaculation latency in an experience-dependent fashion. (2015)
- mGluR5 activation in the nucleus accumbens is not essential for sexual behavior or cross-sensitization of amphetamine responses by sexual experience (2016)
- Influences of dopamine and glutamate in the medial preoptic area on male sexual behavior.(2014)
- Postcoital Dysphoria: Prevalence and Psychological Correlates (2015)
- The human sexual response cycle: brain imaging evidence linking sex to other pleasures (2012)
- Glutamatergic transmission is involved in the long lasting sexual inhibition of sexually exhausted male rats. (2015)
- Psychological Symptoms in a UK Population Sample of Female Twins (2011)
- The Prevalence and Correlates of Postcoital Dysphoria in Women (2011)
- Electrical stimulation of dorsal and ventral striatum differentially alters the copulatory behavior of male rats (2010)
- Endogenous opioids mediate the sexual inhibition but not the drug hypersensitivity induced by sexual satiation in male rats (2013)
- IRS2-Akt pathway in midbrain dopamine neurons regulates behavioral and cellular responses to opiates (2007)
- Lateral Hypothalamic Serotonin Inhibits Nucleus Accumbens Dopamine: Implications for Sexual Satiety (1999)
- Opiate-Induced Molecular and Cellular Plasticity of Ventral Tegmental Area and Locus Coeruleus Catecholamine Neurons (2012)
- Pharmacological and physiological aspects of sexual exhaustion in male rats (2003) (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.)
- Recovery from sexual exhaustion-induced copulatory inhibition and drug hypersensitivity follow a same time course: two expressions of a same process? (2010)
- Relationship Between Sexual Satiety and Brain Androgen Receptors (2007) (reduction in sexual activity in sexually-satiated rats was accompanied by reduction in androgen receptors. 72 hours later, androgen receptors had returned to normal. Testosterone levels did not change during recovery)
- Relationship between sexual satiety and motivation, brain androgen receptors and testosterone in male mandarin voles (2013)
- Exposing orgasm in the brain: a critical eye (2012)
- Sexual Behavior Reduces Hypothalamic Androgen Receptor Immunoreactivity (2003)
- Sexual Behavior and Sex-Associated Environmental Cues Activate the Mesolimbic System in Male Rats (2004)
- The mesolimbic system participates in the naltrexone-induced reversal of sexual exhaustion: Opposite effects of intra-VTA naltrexone administration on copulation of sexually experienced and sexually exhausted male rats (2013)
- The post-orgasmic prolactin increase following intercourse is greater than following masturbation and suggests greater satiety (2006)
- c-Fos expression related to sexual satiety in the male rat forebrain (2007)
- Dopaminergic challenges in social anxiety disorder evidence for dopamine D3 desensitisation following successful treatment with serotonergic antidepressants (Low dopamine associated with social anxiety. Many porn users and POIS sufferers report desire for isolation and/or social anxiety after orgasm.)
- Anabolic androgens restore mating after sexual satiety in male rats (long term inhibition of masculine mating behavior after repeated ejaculations and is associated to changes in both androgen receptor and estrogen receptor-alpha expression)
- A research on the relationship between ejaculation and serum testosterone level in men (testosterone fluctuates for 7 days after ejaculation)
- Sexual behavior reduces hypothalamic androgen receptor immunoreactivity (sexual activity reduces androgen receptors in specific brain areas, even when they remain normal in blood, and may underlie sexual satiety)
- Hormone-neurotransmitter interactions in the control of sexual behavior (overall view of neurotransmitter involved in sexual behavior)
- Hormonal responses to different sexually related conditions in male rats (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 (Sexual activity reduces androgen receptors in specific brain areas, and androgens regulate sexual desire through activating reward circuitry dopamine levels. Possibly, the reduction in androgen receptors in reward circuit (mpoa), seen in other experiments, which can last a week, are one major cause of low dopamine in reward circuit following orgasm (in addition to prolactin surges.)
- Effects of testosterone metabolites on copulation and medial preoptic dopamine release in castrated male rats (testosterone acts through reward circuit dopamine to affect sexual desire)
- Hormone-neurotransmitter interactions in the control of sexual behavior (evidence that testosterone works by activating dopamine in reward circuit)
- The post-orgasmic prolactin increase following intercourse is greater than following masturbation and suggests greater satiety (400 percent more prolactin after intercourse than after masturbation...biology's way of signaling that the critical job is done)
- Circulating neuroactive c21- and c19-steroids in young men before and after ejaculation (level of 17alpha-hydroxypregnenolone increased significantly, whereas the other circulating steroids - including DHEA - were not changed at all.)
- Coitus-induced orgasm stimulates prolactin secretion in healthy subjects (orgasm leads to elevation of blood prolactin) (2001)
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Evidence for changes in brain enkephalin contents associated to male rat sexual activity (2002) (Changes in opioid levels occur in brain following orgasm. 48 hours after orgasm opioids levels had not returned to normal in the hypothalamus (reward circuit). No differences in the magnitude of the changes were found between rats that ejaculated once and sexually satiated males.)
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Involvement of endogenous opioidergic neurons in modulation of prolactin secretion in response to mating in the female rat. (opioids released during mating have inhibitory influence on sexual behavior — by increasing prolactin)
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Prolactin secretory rhythm of mated rats induced by a single injection of oxytocin (Oxytocin surge at orgasm may cause post-orgasmic prolactin.) Complete study
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Neuroendocrine response to film-induced sexual arousal in men and women (prolactin doesn't rise before orgasm - full article)
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Men's Sexual Problems Linked to Low Prolactin Levels (as well as too high levels)
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Prolactin secretion patterns: basic mechanisms and clinical implications for reproduction
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NMDA-Mediated Activation of the Medial Amygdala Initiates a Downstream Neuroendocrine Memory Responsible for Pseudopregnancy in the Female Rat (prolactin surges continue for 2 weeks after female rats mate, even if no pregnancy occurs)
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Prolactin release after mating and genitosensory stimulation in females(Intromissions induce the 10-13 days of twice-daily prolactin surges. There is a threshold that has to be met for the full response to occur.)
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Specificity of the neuroendocrine response to orgasm during sexual arousal in men (Prolactin regulates sexual appetite through dopamine. Oxytocin rises at orgasm but is inconsistent compared to prolactin.)
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Orgasm-induced prolactin secretion: feedback control of sexual drive? (Prolactin increases significantly at orgasm and functions to regulate sexual desire. Sexual activity without orgasm doesn't raise prolactin levels.)
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Absence of orgasm-induced prolactin secretion in a healthy multi-orgasmic male subject (prolactin typically increases significantly at orgasm and functions to regulate sexual desire)
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Prolactinergic and dopaminergic mechanisms underlying sexual arousal and orgasm in humans (Dopamine underlies sexual arousal. Prolactin inhibits sexual appetite and may be implicated in orgasmic disorders)
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Effects of acute prolactin manipulation on sexual drive and function in males (elevation of prolactin after orgasm affects central nervous system centers controlling sexual drive and behavior)
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Prolactin: An integral player in hormonal politics (full article by Dr. Heaton on prolactin's effects on sex)
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Ecstasy (MDMA) mimics the post-orgasmic state: Impairment of sexual drive and function during acute MDMA-effects may be due to increased prolactin secretion (impairment of sexual parameters after ecstasy may be caused by increased prolactin)
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Brain areas activated after ejaculation in healthy young human subjects (spatiotemporal activation in amygdala during 30 minutes after ejaculation)
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Yohimbine interacts with the dopaminergic system to reverse sexual satiation: further evidence for a role of sexual motivation in sexual exhaustion (dopamine agonists stimulated sexual behavior in satiated rats)
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Induction of mating behavior by apomorphine in sexually sated rats (inhibition of sexual behavior follows blockage of dopamine - but other neurotransmitters involved)
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Activation of mu opioid receptors in the medial preoptic area following copulation in male rats (changes in opioid receptors in reward circuit (mpoa) involved in sexual behavior — inhibitory influence on sexual behavior)
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Hormone-neurotransmitter interactions in the control of sexual behavior (Serotonin is involved with sexual satiation mechanism. Serotonin inhibits reward circuit dopamine)
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Centrally released oxytocin mediates mating-induced anxiolysis in male rats (Oxytocin critical to change of behavior male rats for several hours after coitus. They take more risks and seem less fearful.)
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Prolactin secretory rhythm in women: immediate and long-term alterations after sexual contact
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A mathematical model for the mating-induced prolactin rhythm of female rats (Injection of oxytocin sets off prolactin rhythm in rats)
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Relationships among cardiovascular, muscular, and oxytocin responses during human sexual activity. (Plasma oxytocin shoots up and drops within minutes at masturbation-induced orgasm. Levels not linked to intensity...except in multi-orgasmic women.)
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Plasma oxytocin increases in the human sexual response. (Plasma oxytocin shoots up and drops within minutes at orgasm. May be linked to smooth muscle contractions of the reproductive system during orgasm.)
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The neurobiology of pair bonding (Entire article on neurobiology of pair bonding - excellent overview of sexual neurochemistry)
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Oxytocin receptor is expressed in the penis and mediates an estrogen-dependent smooth muscle contractility (oxytocin spurt at orgasm may play a role in penile flaccidity)
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Oxytocin Mediates the Estrogen-Dependent Contractile Activity of Endothelin-1 in Human and Rabbit Epididymis (oxytocin plays a role in spontaneous motility necessary for sperm transport)
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Neural activation following sexual behavior in the male and female rat brain (there is a specific ejaculation-related subcircuit, which may, under normal conditions in the rat, serve a 'sexual-satiety function')
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Changes in the sexual behavior and testosterone levels of male rats in response to daily interactions with estrus females (when male rats have daily sexual interactions, sexual behavior tends to show 4-day cyclic changes and testosterone is significantly elevated only on the first day of interactions)
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Sexual activity is inversely related to women’s perceptions of the facial attractiveness of unknown men (the more sexual activity women engage in, the less attractive they find men. This effect is strongest with respect to masturbation and least strong with respect to penile-vaginal intercourse)
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The endocrinology of sexual arousal (Review by Bancroft, mentions 15-day recovery by male rats)
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.
- Cell-type specific increases in female hamster nucleus accumbens spine density following female sexual experience (2013) (life experience with a naturally motivated behavior has the capacity to induce persistent structural alterations to the mesolimbic circuit that can increase reproductive success and are analogous to the persistent structural changes following repeated exposure to many drugs of abuse)
- Changes in gene expression within the nucleus accumbens and striatum following sexual experience (2005)
- Concurrent exposure to methamphetamine and sexual behavior enhances subsequent drug reward and causes compulsive sexual behavior in male rats (2011)
- Delta JunD overexpression in the nucleus accumbens prevents sexual reward in female Syrian hamsters (2013)
- DeltaFosB Overexpression In The Nucleus Accumbens Enhances Sexual Reward In Female Syrian Hamsters (2009)
- DeltaFosB in The Nucleus Accumbens is Critical For Reinforcing Effects of Sexual Reward. (2010)
- DeltaFosB: A Molecular Switch for Reward (2013)
- Pathways of sexual desire (2009) Brain dopamine systems appear to form the core of the excitatory system. This system also includes melanocortins, oxytocin, and norepinephrine. Brain opioid, endocannabinoid, and serotonin systems are activated during periods of sexual inhibition, and blunt the ability of excitatory systems to be activated.
- Endogenous opioid-induced neuroplasticity of dopaminergic neurons in the ventral tegmental area influences natural and opiate reward (2014)
- Methamphetamine acts on subpopulations of neurons regulating sexual behavior in male rats (2010)
- Natural and Drug Rewards Act on Common Neural Plasticity Mechanisms with ΔFosB as a Key Mediator (2013)
- Natural reward experience alters AMPA and NMDA receptor distribution and function in the nucleus accumbens (2012)
- Natural Rewards, Neuroplasticity, and Non-Drug Addictions (2011) (discusses cross-sensitization between sexual experience and drug reward)
- Neuroplasticity in the Mesolimbic System Induced by Natural Reward and Subsequent Reward Abstinence. (2010) (long-lasting effects of both sexual behavior and drugs are mediated by common cellular or molecular mechanism)
- Sexual Behavior Induction of c-Fos in the Nucleus Accumbens and Amphetamine-Stimulated Locomotor Activity Are Sensitized by Previous Sexual Experience in Female Syrian Hamsters (2001) (sexual behavior can speed addiction to amphetamines, because it appears to cross-sensitize neuronal response in the nucleus accumbens)
- Sexual experience alters D1 receptor-mediated cyclic AMP production in the nucleus accumbens of female Syrian hamsters (2004)
- Sexual experience in female rodents: cellular mechanisms and functional consequences (2006)
- Sexual experience sensitizes mating-related nucleus accumbens dopamine responses of female Syrian hamsters (1999) (higher levels of prior sexual experience equal higher levels of dopamine in reward center)
- Sexual reward in male rats: Effects of sexual experience on conditioned place preferences associated with ejaculation and intromissions (2009)
- The Influence of ΔFosB in the Nucleus Accumbens on Natural Reward Related Behavior (2008)
- Recovery from sexual exhaustion-induced copulatory inhibition and drug hypersensitivity follow a same time course: two expressions of a same process? (2011)
- Brain Activation during Human Male Ejaculation (Holstege's description of results compared brain scans of ejaculation with brain scans of heroin use)
Implications for pair-bonding mammals
- Reward Mechanism Involved in Addiction Likely Regulates Pair Bonds Between Monogamous Animals (press release about elements of addiction in bonding)
- Amphetamine reward in the monogamous prairie vole (the neural regulation of pair bonding in the monogamous prairie vole is similar to that of drug seeking)
- Nucleus accumbens dopamine mediates amphetamine-induced impairment of social bonding in a monogamous rodent species (amphetamine impairs pair bonding in monogamous voles)
- Social Bonding Decreases the Rewarding Properties of Amphetamine through a Dopamine D1 Receptor-Mediated Mechanism (pair-bonding experience decreases the rewarding properties of amphetamine via dopamine receptor mechanism)
- The behavioral anatomical and pharmacological parallels between social attachment love and addiction
- Biological Contribution to Social Influences on Alcohol Drinking: Evidence from Animal Models
(Naltrexone, an opioid receptor antagonist approved as a pharmacotherapy for addicts, decreases both partner preference and alcohol preference in monogamous voles.)