Moody Bitches: The Truth about the Drugs You’re Taking, the Sleep You’re Missing, the Sex You’re Not Having and What’s Really Making You Crazy.... Julie Holland

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, relaxed, sexually satisfied, and satiated sensation. In some women after orgasm, a negative feedback loop is triggered, with prolactin secretion making them sleepy, dopey, and, often, significantly less horny. Still other women respond to the heightened pleasure with one thought in mind: I wanna go again. Sometimes all that dopamine, norepinephrine, and testosterone continue to trigger sexual desire. Also, the oxytocin creates more touch sensitivity and a desire for more skin-to-skin cuddling, which can trigger another round of testosterone surge.

      Brain Blood Flow in Orgasm—All the Wonky Details

      Barry Komisaruk’s lab at Rutgers University in northern New Jersey is the world’s largest orgasm research laboratory. Here, men and women are slid into an MRI chamber, where they must lie completely still, their heads held immobile in a mesh cage. Their brain blood flow is then measured while they give themselves, or receive, orgasms. Over the years, this lab has studied just what it takes to climax, including looking at women who can orgasm through fantasy alone and others who’ve had their spinal cords severed, to see if they can climax. (They can, as long as their vagus nerve, which innervates the genitalia, is intact.)

      The lab’s more recent studies are delineating the difference between self-stimulation and partner stimulation. Most of us would be quick to agree that these two orgasms are qualitatively different, especially in the emotional realm. The question is: are they physiologically different? Early results suggest they are.

      During orgasm, fresh oxygen- and nutrient-rich blood floods the brain. Leading up to orgasm, a series of brain blood flow changes occur. First is activation of the somatosensory cortex, the part of the brain that maps out bodily sensations. Next seen is decreased blood flow to the frontal cortex. You want less frontal flow because you need your foot off the brakes to move a car forward. Frontal inhibition will put the kibosh on the entire sequence. Soon after, the secondary somatosensory cortex, which adds the emotional piece to your physical sensations, is activated. Then increased blood flow is seen in the amygdala, your emotional center, and then in the part of the hypothalamus that is responsible for the release of oxytocin.

      The last piece of the puzzle is the dopamine circuitry that underlies reward seeking, pleasure, and euphoria. The final push into orgasmic bliss is the job of this brain area. Dopamine not only helps you pay attention, focus, and keep your eyes on the prize, but it also marks an event as salient. So don’t be surprised if the guy you were only moderately into suddenly becomes more important in your eyes after he’s given you the big O. Dopamine surges also decrease sensory thresholds for more sensation, priming the brain for more pleasure. Multiple orgasms, anyone? (For more on sexual pleasure, please enjoy the sex chapter.)

Four

       Marriage and Its Discontents

      The chemistry of attraction changes over time, ebbing over six to eighteen months, being slowly supplanted by the chemistry of attachment. Committed love is calmer, with none of the sweaty palms and churning stomach, thanks to less circulating dopamine, norepinephrine, and phenylethylamine (PEA). Because of that seesaw effect, lower dopamine means higher serotonin. The reward circuitry isn’t firing, and the frontal lobes are fully online, so rational thought wins out over emotional upheaval, due to normalized serotonin levels. The study comparing the serotonin levels of patients with OCD to those who were infatuated showed that the levels do finally normalize during the attachment phase, as your lover becomes less of an obsessive fixation. Less dopamine also means less testosterone, for both of you, so the lust factor has died down considerably. Men’s testosterone levels are lower after they’ve been partnered for more than a year compared to those in the first six months of a committed relationship.

      Recall the dads-versus-cads issue. In men, higher levels of testosterone (cad) can reduce the attachment drive. A manly guy may be great pickings for a one-night stand and may provide top-shelf genetic material, but it may not be in his nature to stick around to change diapers. Birds that are