to sex, taking the brakes off and helping us to be uninhibited, but testosterone is the gas pedal. Even flirting seems to have some basis in testosterone. While romantic love is reserved for one preferred partner, the target of lust isn’t the perfect man, but rather “almost any semi-appropriate partner”; it’s not Mr. Right so much as Mr. Right Now. Also, the neural mechanism of attraction won’t allow you to fall in love with two different people at once, but you can lust after more than one person at a time. Another key difference is that the fires of lust are quickly doused once the sex is over; with attraction, repeated sex just adds to the buildup of good feelings.
In women, testosterone is made in the adrenal glands and ovaries, spurring our competitive drive, our assertiveness, and our lust. In adolescence, a girl’s level of testosterone rises five times above normal, but it is in the context of her estrogen increasing ten to twenty times above normal, so it’s balanced out to a large extent. Adolescent boys have a twenty-five-fold increase in their testosterone, unabated by other mitigating hormonal factors, which means they have much higher sex drives than the girls. Also, in boys these levels are static, whereas girls have cyclical variation. Boys’ behavior ends up being much more consistent, basically a constant stream of horny. Boys have more frequent sexual thoughts and more masturbation, which is not to say girls aren’t doing it, too, just not as much. Interestingly, surging testosterone levels in an adolescent girl can signal the time of first intercourse.
Women have different standards for hookups versus getting hitched. In the past few years, numerous articles have been written about how today’s women, whether in college or out in the world soon after, are so focused on getting their careers off the ground that they prefer more casual sex over complicated long-term relationships. They’d rather get their gratification on their own terms and not muck it up with messy feelings like love. Since “women’s lib” and oral contraceptives have become commonplace, women have had growing freedom in this arena. Having sex has become uncoupled from committed relationships and the responsibilities of motherhood. This is a relatively new phenomenon, and I totally get it. But one warning about one-night stands, just so you aren’t fooling yourself. Lust and sex can trigger feelings of attraction and even love. Rising testosterone levels can enhance dopamine and norepinephrine transmission and lower serotonin, matching the brain chemistry of someone who’s falling in love. And sex can definitely trigger attachment and bonding, due to oxytocin. Testosterone can trigger oxytocin release, and an orgasm will definitely trigger oxytocin release. If you orgasm or cuddle after sex, the bonding hormones may sneak up on you, though you intended your sex to be casual. Thanks to oxytocin, you may find yourself with loving, attached feelings for your Mr. Right Now.
There is a strong desire in women to be held and cuddled. Many of us will use sex as a means to an end, hoping to have some afterglow and snuggling, willing to trade sex for that experience. Men, too, are eager to be held. A common complaint among men in sex therapy is that they don’t receive enough nonsexual touching. But getting naked and cuddling is going to trigger oxytocin, the bonding hormone. So you may find that it’s hard for you to keep your “friend with benefits” in that same category for long.
The Chemistry of Sex
Your brain on sex is like a series of loops. Hormones may trigger behaviors, but just as often, behaviors trigger hormones. Sexual activity stimulates testosterone release, which further revs up desire and triggers dopamine release. This dopamine-laden euphoria and arousal further trigger testosterone release. Sensitivity to touch is enhanced by dopamine and particularly by oxytocin. The more skin-to-skin contact, cuddling, kissing, eye gazing, and nipple stimulation, the more oxytocin gets released, which triggers testosterone, then dopamine.
Oxytocin and endorphins not only stoke arousal and pleasure but also help produce feelings of closeness and relaxation. As a woman becomes aroused by stimulation of her nipples, oxytocin gets released, just as it is when suckling a newborn. Further attention to her vagina, clitoris, or cervix creates more oxytocin and estrogen release, resulting in an acute drive to become penetrated, and an expansion of the vaginal muscles in case that’s what will happen. Estrogen is involved in every phase of sex, making women more sexually receptive and lubricated and triggering oxytocin release. As sex progresses, oxy increases, culminating in an orgasmic burst. Estrogen and testosterone put the brain on high alert, so that dopamine and norepinephrine, our two “stand up and take notice” chemical friends, can get involved. Dopamine, of course, makes us pay attention to a potentially rewarding stimulus like sex. It gives us pleasure, enhances sensory input, and triggers the reward circuitry that motivates us to keep going, driving us toward orgasm.
You have two competing systems in your body: sympathetic and parasympathetic. The sympathetic is the fight-or-flight system, while the parasympathetic is the rest-and-digest system. Norepinephrine jump-starts the sympathetic nervous system, increasing heart rate, raising blood pressure, and causing heavy breathing. Balancing this out, the parasympathetic system also gets in on the act, directing blood flow to the genitals. Sex is a delicate balance of sympathetic and parasympathetic stimulation, toggling back and forth. Too much adrenaline-like arousal early on, and plateau or orgasm may be difficult, if not impossible, as is seen with stimulants like cocaine and speed. (There are those people, though, who need a short burst of adrenaline in order to get over the finish line.)
For the finale, endorphins take center stage, helping us to feel great and make sex something we’ll want to do repeatedly. Endorphins also raise our pain threshold. Response to pain is just half of normal during the peak of sexual arousal. Does that help explain nipple clamps? Not only do they hurt less when you’re extremely aroused and high on your brain’s own heroin, but there is some overlap in the brain when it comes to sexual pleasure and pain, as their circuitry is closely linked. If you’re also curious about anal sex or toe sucking, anal sensations travel some of the same routes as genital sensations, and the area in the brain that maps out physical sensations from the genitals is right next to the one for the toes. Stimulate either area enough and you get some carryover into the genital sensation part of the brain. And breast and genital neural circuitry overlap as well, which may explain why some women can orgasm from nipple stimulation alone. Isn’t the brain marvelous? Also, there is mounting evidence that sexual pleasure triggers the endocannabinoid system as well, your body’s internal cannabis molecules.
The Chemistry of Orgasm
Orgasms are good for you. They reduce mortality, are good for your heart and cardiovascular system, help to prevent endometriosis, and when the time is right, they help you to conceive and carry a pregnancy to term.
The beginning of sexual pleasure is dopamine mediated, while the second act is primarily endorphins, which crescendo with orgasm. Oxytocin and dopamine are the big players leading up to orgasm, but the climax itself owes its mind-bending effects to the triple threat of oxy, endorphins, and PEA, the hallucinogen-like brain chemical, which just might make you feel like you really were “way out there” when you climaxed. Trippy, out-of-body experiences, or laughing, crying, and switching between the two, are all possible and normal during an orgasm.
Oxytocin keeps you feeling connected to your lover. It also permits relaxation, helping you feel calm, secure, and trusting enough to climax. Peaking at orgasm, oxytocin causes uterine contractions, which help to “suck up” semen into the cervix. It also can engender tremendous feelings of openness, trust, and bonding. The oxy afterglow lasts between one and five minutes postorgasm in women.
After orgasm, serotonin peaks, creating one happy,
