Neurochemistry

Brain in love (diagram)
A 2014 Human Touch of Chemistry diagram on neurochemicals, such as Dopamine, Norepinephrine, and oxyctocin, and neuroanatomy, such as the prefrontal cortex, amygdala, hippocampus, pituitary gland, nucleus accumbens, and the ventral tegmental area. (Ѻ)
In chemistry, neurochemistry is the study of the chemical function and operation of the nervous system. [1]
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Overview
Neurochemistry includes the study of cellular neurochemistry and neural membranes; intercellular signaling; intracellular signaling; growth, development, and differentiations; metabolism; inherited and neurodegenerative diseases; sensory transduction; and neural processing and behavior. [2]

In human chemistry, research efforts over the last few decades has focused on how various neurochemicals, in particular: oxytocin, vasopressin, endorphin, dopamine, serotonin, norepinephrine, testosterone, estrogen, epinephrine, phenylethylamine (PEA), dehydroepiandrosterone (DHEA), brain-derived neurotropic factor (BDNF), monoamine oxidase (MAO), gamma-aminobutyric acid (GABA), prolactin, cortisol, progesterone, estradiol, nerve growth factor (NGF), gonadotropin-releasing hormone (GNRH), among others, related to various moods, e.g. happiness, and states of human existence, e.g. being in love, in relation to changes in human bonding. [3]

Neurochemicals
The following bulleted terms—a paste from American electrochemical engineer Libb Thims’ 2007 section “Neurochemicals”, from his Human Chemistry (Volume Two), numbered non-bracketed references found therein—are the main neurochemicals related to human behavior and bonding, along with related neuroanatomical areas and terms: [3]

Oxytocin [C43H66N12O12S2] – bonding molecule (hormone): high levels correlate with strong pair-bonding; sometimes called the ‘cuddle chemical’; levels rise during touching, kissing, and foreplay, and peak during orgasm. Is considered the ‘hormone of love’.123 Associated with male-female attachment.124 Is made in the hypothalamus, ovaries, and testes.122 Is released in women during the birthing process.125 Initiates contractions of the uterus, stimulates the mammary glands to produce milk, and stimulated bonding between a mother and her infant.126 At orgasm, levels increase dramatically in women.126 Released during stimulation of the genitals and nipples.127 Is secreted in response to the crying of the infant.11 Thinking about a loved one will cause levels to rise.128 It reduces stress.128 It makes people forgetful and diminishes the capacity to think and reason.128 Is secreted in the posterior lobe of the pituitary gland.128 When given to females around ovulation, it heightens their efforts to contact males and intensifies lordosis, i.e. sexual presenting.128 When given to males, they will develop maternal behaviors and infant guard ferociously; when levels are artificially blocked in males, they will neglect their infants and may even eat them.128 Improves erection, speeds ejaculation, enhances contractions of penile tissue, and increases ejaculation volume and sperm count; conversely, lowered levels reduces sperm count.128 Penis-vaginal contact and penetration increases levels in both sexes.128

| → Oxytocin theory of love

Oxytocin, according to intranasal administration studies, is found to affect people’s responses to moral dilemmas that pit in-group members against out-group members, making them less comfortable with sacrificing in-group members, but not out-group members. [4]

Vasopressin– monogamy molecule (hormone); responsible for creating intense loving memories during passionate situations; responsible for clarity of thought and alertness during passionate situations. Associated with male-female attachment.122 Ejaculation increases levels of in the brain, triggering spousal and parenting zeal.129 When injected into the brain it causes males to engage in territorial defense behaviors from other males and to become extremely possessive of the female[s] in his territory.130 When the production of in the brain is artificially blocked, males will copulate with a female and then abandon her for another mating opportunity.130 Is made in the hypothalamus, ovaries, and testes.122 At orgasm, levels increase dramatically in men.131 Released during stimulation of the genitals and nipples.127 Works with testosterone, modulating male sexual behavior, keeping it from reaching extremes or becoming too hot, i.e. it has a tempering influence.128 It turns a person’s attention from the abstract to the concrete, away from the past and future to the here and now, and appears to improve memory, cognitive powers, and concentration.128 Secreted from the posterior pituitary gland.128 It increases attention and alertness while reducing emotionalism.128 A deficiency of causes a reduction of REM sleep.412 Artificially increased levels of induces flank-marking behaviors, thus communicating status and instilling dominant-subordinate heirarchies.128

Endorphin (endogenous opioid) - calming natural pain killer; levels increase in response to touch, pleasing visual stimulus (as a smile), or after dwelling on positive thoughts.128 Thought to be the main attachmentchemical in long-term relationships.132 Is associated with love.126 Exercise elevates levels of some of the endorphins, instilling a calming effect.122 Stroking and massage trigger the production of, which causes a person to relax, and produces feelings of attachment.133 Reduces separation-induced crying.134 Secreted in situations of social comfort and produce a sense of well-being.134 When people feel socially cut off the brain’s production of decreases, which makes people feel anxious and even panicky.134 When deprived of an important social bond our levels shut down; with the passage of time, however, the system begins to prime itself again as receptors become more sensitive and storage pools increase their stock.134 Dwelling on positive thoughts can raise levels of.128

| → Endorphin theory of love

Related bonding chemicals
The following are the main neurochemicals involved in human bonding (human chemical bonding):
SunlightGoal (dopamine)
A WikiHow image (Ѻ) of how as little as 10-15 minutes of sunlight exposure (#2) can work to open up more dopamine receptors, therein allowing the mind to make more use of available dopamine; the #1 method of increasing dopamine being “setting a goal” for oneself, according to which when one begins to approach the reward, or achievement of the goal, the body releases dopamine, and that with each small step toward the goal, the body releases dopamine, incrementally.

Dopamine [C8H11NO2] – desire molecule (neurotransmitter): levels increase as passion levels increase; elevated levels are associated with romantic love.135 Is produced by specialized nerve cells located in the arcuate nucleus of the brain. Increased levels associated with sexual arousal and heightened motivation.136 Elevated levels directly associated with a preference for a particular mate.137 Mate favoritism is associated with a fifty percent increase in the nucleus accumbens, a part of the brain associated with craving and addiction.138 Reduced levels correlated to indiscriminate mate selection.139 Injected increases of cause females to prefer the male present at the time of the infusion, even if she had never mated with this individual.139 Levels spike as an estrus female looks at slides of a males face.140 Heightened levels associated with extremely focused attention.141 Heightened levels associated with unwavering motivation and goal-directed behaviors.142 All major addictions are associated with elevated levels of.143 Specific brain cells produce greater amounts when a reward is delayed, thus energizing, focusing, and driving the pursuer harder.144 All basic drives, and particularly sexual drive or motivation, are associated with elevated levels of.145 Stimulates the release of testosterone.146 Elevated levels are related to sexual arousal, frequency of intercourse, and positive sexual function.147 When injected into the blood stream it stimulates copulatory behaviors.148 When a male is near an estrous female, such that he can see or smell her, his levels rise.149 During copulation levels rise.150 Stimulates lust and erectile function.151 Drugs that elevate levels of in the brain cause sex drive to improve.152 Very high levels of are associated with intense motivation and goal-directed behaviors, as well as with anxiety and fear.133 Vigorous exercise drives up levels of dopamine in the nucleus accumbens, bestowing feelings of euphoria.153 Twice as many receptors for dopamine are found in the limbic systems of schizophrenics.154 Is responsible for the desire or pursuit of any pleasure [see: pleasure center]; without it, a person will feel no joy, anticipation, enthusiasm, excitement, or exuberance.128 It is the common denominator of most addictions, such as cocaine and alcohol, and may be what addicts people to each other.128 It is the neurotransmitter that moves people, drives them to go after what they want, reinforces that desire, and promotes the anticipation of pleasure.128 Is what makes a person smile as well as induces spontaneous activity and movement.128

| → Neuroeconomics
Prozac (serotonin)
A 1987 timeline clip from Forbes 18 Dec 2017 100th anniversary issue, discussing the invention of Prozac, which artificially increases serotonin. [5]

Serotonin [C10H12N2O] – stability molecule (neurotransmitter). Selective serotonin reuptake inhibitors, such as Prozac or Zoloft, work to elevate levels of and thus alleviate aberrant behaviors such as obsessive-compulsive disorders.155 During the first six months of love, serotonin levels drop to forty percent below those in normal subjects.156 Low levels are attributed to a lover’s persistent, involuntary, irresistible ruminations, e.g. up to ninety percent of one’s waking hours, about a loved one.157 Both those newly in love within the previous six months and those will obsessive-compulsive disorder have lower levels of.158 Rising levels of dopamine and norepinephrine cause levels to plummet.159 Exercise elevates serotonin.122 Women taking SSRI’s, i.e. serotonin boosters, rate male faces as less attractive than compared to non-medicated women and spend less time looking at the faces.122 Serotonin enhancer drugs dampen the sex drive and tends to inhibit the sex response.122 High levels cool one’s sex drive; low levels intensify it.128 High levels instill a peaceful nature in a person, reduce sex drive, and delay orgasm.128 High levels promote selectivity in mates, namely same species and heterosexual choice; low levels promote indiscriminate sexual choice of partner and gender.128 Those with low levels will tend to participate in group sex, in a violent and often frenzied nature.128 Low levels promotes responsiveness; in females, orgasms come more quickly; in males, ejaculations come quicker.128 Levels decrease with dieting often added to the sex drive as body image improves.128 Lower levels of in females will cause them to mount other females and smaller males and behave more like males.128

Norepinephrine [C8H11NO3] - elevated levels are associated with romantic love.135 Is a precursor of epinephrine (adrenaline) in its major biosynthetic pathway.160 Increased levels associated with sexual arousal and heightened motivation.161 The smell of male urine causes levels to increase in the female brain.162 Levels spike as an estrus female looks at slides of a male’s face.140 Heightened levels associated with lordosis.163 Increasing levels produce exhilaration, excessive energy, sleeplessness, and loss of appetite.122 Is associated with increased memory for new stimuli, especially social memory.164

Testosterone [C19H28O2] – masculinization hormone (high testosterone-laden males tend to bond with high estrogen-laden females); levels drop in men who are involved in long-term monogamous relationships; functions as the main sex drive hormone for both men and women.135 It is the hormone of sexual desire and associated with lust in both men and women.122 Men and women who have higher circulating levels of engage in more sexual activity.165 Male athletes who inject themselves with it tend to have more sexual thoughts, more morning erections, more sexual encounters, and more orgasms.122 Women who take supplement of in middle age boost their sexual desire.165 Women feel more sexual desire around ovulation, when levels increase.166 When males see a sexually available female or watch a companion copulate with a female, their levels soar.167 Increased levels of works to elevate levels of dopamineand norepinephrinebut to suppress levels of serotonin.122 Men with high levels of marry less frequently, have more adulterous affairs, commit more spousal abuse, and divorcemore often.122 As a man’s marriage becomes less stable, his levels rise and with divorce his levels rise further.122 Single men tend to have higher levels than married men.168 As a man becomes more and more attached to his family, levels decline.169 At the birth of child, expectant fathers experience a significant decline in levels of.169 When a man holds a baby his levels decrease.122 Increasing levels of can sometimes drive down levels of vasopressin (and oxytocin) and elevated levels of vasopressin can decrease levels of.170 High levels of reduce attachment.122 High levels of inhibit nurturing behavior in both males and females.171 Lowers the firing threshold of the amygdala, the area of the brain most involved with violence and agression.172 Is responsible for the aggressive sex drive, makes one want to pursue sex, initiate, and dominate.128 It stimulates desire directly by enhancing levels of dopamine, a neurotransmitter known to increase sex drive.128 Without testosterone males won’t mark their territory or confront intruders; with it, they fight to protect their turf, take ownership of their mates, and often wish to be aloof or alone.128 Is a potential aphrodisiac for both males and females, promoting the drive for genital sex and orgasm.128 Promotes masturbation, one-night stands, and a decreased desire for emotional entanglements.128 It doubles as an anti-depressant, but makes people irritable when it spikes.128 Levels drop in men who live together.128 Is extremely sensitive to environmental stimuli, e.g. a confrontation, competition, stress, or the presence of other men or women.128 Higher levels of in the male increases the attractiveness of the male odors to the female.128 Levels rise in those who are victorious in combat.128 Men with high levels of are less likely to get married and more likely to have affairs if they do marry.128

Estrogen– feminization hormone (high estrogen-laden females tend to bond with high testosterone-laden males). Attractiveness to men is enhanced by it.128 It governs the female receptive sex drive and makes a female acquiescent to a man moved to pursue her by testosterone.128 Generates attractive body odor and texture.128 Promotes vaginal lubrication and promotes lordosis.128 In regards to behavior, it prevents depression, reduces stress, improves sense of taste and smell, and decreases appetite.128

Epinephrine (adrenaline) [C9H13NO3] – a basic sympathomimetic stimulate hormone, e.g. it causes a person’s heart to race.160 A mixture of danger, fear, and adventure, e.g. riding on a roller coaster or walking on high creaky suspension bridge, stimulates levels of and new couples are more likely to attach to each other following dates where levels were high.173 Makes a person more happy in a pleasant situation, but more angry in a frustrating one.134
A 2008 neurochemistry talk on PEA and oxytocin in love and attachment by Croatian neuroscience researcher Marko Kosicek.

PEA [C8H11N] – amphetamine-like molecule (neurotransmitter) often known as the ‘molecule of love.’128 It speeds up the flow of information between nerve cells.132 Keeps one alert, confident, and ready to try something new.132 Causes people to feel optimistic of the future, sleep less, and be more socially out-going.134 Low levels have been correlated with love sickness.122 Is considered the visual component of the chemistry of love, in that its levels surge in the sight of someone desirable or even a picture, art, or something one reads.128 Levels are typically higher in women, particularly at ovulation, than in men.128 Levels are high in schizophrenics and during a divorce.128

DHEA [C19H28O2] – most abundant hormone in the body; increases sex drive and influences who one finds attractive; levels increase to three to five times that of baseline before and during orgasm. Because most of the other sex hormones are derived from it, it thus unconsciously tells a person when they can or cannot have sex.128 Pheromones are derived from it.128 Responds directly to both emotional and environmental stimuli and drops drastically under stress.128 Through the action of pheromones, it acts on the brain to influence our choice of mates.128 Lean females have double the amount of it than obese females.128 It excites the septum and medial preoptic areas, which are known to promote active and pleasurable sexual behavior and reactions.128 When males are exposed to the scent of receptive females for seven days, levels are increased in the amygdala and hypothalamus.128 Vigorous exercise, for about thirty minutes per day, for one month, causes a measurable increase in levels of.128

Brain-Derived Neurotropic Factor [BDNF] – exercise increases levels of in the hippocampus, the memory center, which protects and makes new nerve cells.122 Exposure to stress and the stress hormone corticosterone has been shown to decrease the gene expression of, and leads to an eventual atrophy of the hippocampus if exposure is persistent.174

Monoamine oxidase(MAO) – one of the most important brain enzymes involved in the regulation of emotions and is a major metabolizer of norepinephrine, dopamine, serotonin, and PEA.134 Men with lower levels of tend be sensation-seekers, with a preference for wild or disinhibited forms of behavior and a particular distaste for anything that smacks of routine or is tedious or boring.134 Those with lower levels are often more social, more active, more playful, and sleep less.134 People with low levels of seem to have, and to prefer, more intense emotional stimulation in their lives.134 Schizophrenics have lower levels in their blood.175 Is an enzyme that removes a variety of neurotransmitters by oxidation after they have performed their task; a deficiency in MAO would leave excess neurotransmitters at the synapses transmitting information which, in reality, not there.11

Gamma-aminobutyric acid(GABA) – plays and inhibitory role in the brain.11 GABA receptors induce calm by inhibiting or modulating over-reactive neurons.11 Substances such as alcohol and valium have a potentiating effect on GABA synapses, thus instilling a state of calmness.11

Prolactin– motherly hormone (stops female and male sex drive). Is secreted by the pituitary glandand stimulates the growth of mammary tissue and triggers the production of milk.128 When a baby suckles, levels sore to ten times their normal level.128 Women who suckle their infants on a regular basis have a severely reduced sex drive.128 Men with prolactin-producing pituitary tumors often lose their libidocompletely along with their erections.128 Dopamine inhibits prolactin, consequently boosting sex drive indirectly.128 Estrogen gradually increase prolactin secretion, thus diminishing he aggressive sex drive.128 In both men and women, prolactin secretion is increased by exercise, psychological stress, stimulation of the nipples, and sleep.128

Cortisol- the primary hormone product of the adrenal glands; helps restore homeostasis after a state of stress; heightened levels are associated with those newly in loveand with the establishment of new relationships.176 Depressed people have elevated levels beyond what can be explained by the stress they are under.134 The scent of androstadienone, a volatile component of male sweat, causes levels to rise in females.177

Progesterone [C21H30O2] – reverse sex drive hormone; one of the two female sex hormones along with estradiol that during pregnancy begin to rise causing an intensification of a women’s natural femaleness, where she becomes more mothering and nurturing, and while at the same time dampening sexual receptiveness.11 The rapid decrease in progesterone and estradiol after childbirth is accompanied by increased prolactin and oxytocin, which are themselves stimulated to production by the nursing infant’s suckling at it’s mothers’ breast.11 Hormonal treatment of induces maternal behavior towards infants, even those not the mothers.178 It reduces sex drive, by lowering testosteronelevels in both sexes.128 It decreases positive sexual scents, e.g. pheromones, and may make people smell bad to each other, reducing the likelihood of attraction.128 It makes women irritable towards men and aggressive in protecting their young.128 Has a mild sedative, anesthetic, and calming effect.128

Estradiol [C18H24O2] – reverse sex drive hormone; one of the two female sex hormones along with progesteronethat during pregnancy begin to rise causing an intensification of a women’s natural femaleness, where she becomes more mothering and nurturing, while at the same time dampening sexual receptiveness.11 The rapid decrease in progesterone and estradiol after childbirth is accompanied by increased prolactin and oxytocin, which are themselves stimulated to production by the nursing infant’s suckling at it’s mothers’ breast.11 Hormonal treatment of induces maternal behavior towards infants, even those not the mothers.178 Is one of the estrogens that drives the development of secondary sex characteristics in women.179 Promotes maternal behavior by lowering the threshold for the firing nerve fibers in the media preoptic area, an area essential to maternal behavior.180

Nerve growth factor– a neuroprotein that stimulates cell growth; higher levels are found with those newly in loveas compared to those single or in long-term relationships.181

Gonadotropin-releasing hormone (GNRH) – is a pulsatile, rhythmic-release sexual stimulant that reliably increases mating and sexual behavior, e.g. male copulation and female lordosis.128 Heightened levels in males induces them to spend more time near females sniffing, licking, nuzzling, and nipping.128

Neuroanatomy and love
The following are notable neuroanatomical areas associated with love:

Amygdala – when a person begins to realize that an expected reward is in jeopardy, even unattainable, this area together with centers in the prefrontal cortex trigger rage.133 The area of the brain most involved with violence and agression.172 Removal of in violent criminals results in the elimination of the violent behavior.11 Levels of DHEA increase in the area when males are exposed to the scent of receptive females for seven days.128

Limbic system – first system in the brain to switch on when we see someone attractive.134 Is considered to be the central location of the ‘pleasure center’.182 Is the central brain region involved in romance.134

Caudate nucleus – parts of the body and tail of the right caudate nucleus become more active when madly in love and when gazing at a photo of a lover.122 Associated with detection and perception of a reward, discrimination between rewards, preference toward a particular reward, and anticipation of a reward.122 Associated with the acts of paying attention and learning.183

Hypothalamus – synthesizes and secretes neurohormones, often called releasing hormones, as needed that control the secretion of hormones from the anterior pituitary gland. Among other hormones, it releases gonadotropin-releasing hormone (GnRH). The neurons that secrete GnRH are linked to the limbic system, which is primarily involved in the control of emotions and sexual activity.184 Levels of DHEA increase in the area when males are exposed to the scent of receptive females for seven days.128

Septum pellucidum – becomes active when people eat chocolate or when ruminating on an immortal beloved.185 Some refer to it as the pleasure center.11 DHEA excites this area and promotes active and pleasurable sexual behavior and reactions.128

Septum the part of the limbic systemthat regulates emotions and the ability to learn and control impulses as well as such drives as sex, hunger, thirst, aggression, and fear.186 The septum, or septal nuclei, in the brain, named for its approximate shape (partition), receives reciprocal connections from the hippocampus, amygdala, hypothalamus, midbrain, habenula, cingulate gyrus, and thalamus.187 Is rich with nicotonic cholinergic receptors. Is the area of the brain where orgasmic activity is generated.128 When stimulated with electrodes, it causes ecstatic reactions resembling orgasms.128

Ventral tegmental area – parts of the right ventral tegmental area become more active when madly in loveand when gazing at a photo of a lover.122 Is a central part of the reward circuitry of the brain.188 Is the mother lode for dopamine-making cells.122 Its tentacle-like axons distribute dopamine to many parts of the brain, including the caudate nucleus.189

Anterior cingulate cortex – becomes active, for those 2.3-years in love, when gazing at a photo of a lover.190 Is where emotions, attention, and working memory interact.191 Is where a person registers ‘butterflies’ in the stomach and where the mind processes emotions.122

Insular cortex – becomes active, for those 2.3 years in love, when gazing at a photo of a lover.190

Basal ganglia – becomes active when gazing at a photo of a lover.156

Posterior cingulate gyrus – becomes less active when gazing at a photo of a lover.156

Right pre-frontal cortex – becomes less active when gazing at a photo of a lover.156

Frontal lobes – the number of gray cells here is significantly linked to intelligence.192

Pineal gland sunlight is a tonic for depression, i.e. it stimulates this gland, which regulates bodily rhythms in ways that often elevates mood.193

Locus ceruleus – region heavily involved in producing terrifying panic attacks and possibly the anxiety felt when separated from loveones.138
Oleic acid


Myelin sheath – the "white matter" portion of the brain. Those who are petted, messaged, and loved are found to have significantly more of the material necessary for myelin formation.11 A dominant structural component of myelin sheath is oleic acid [C18H34O2], which is found in large amounts in specific oils, such as almond oil or olive oil. Thicker myelin sheath is found to correlated with faster thinking. A notable large number of centenarians on the island of Crete have the habit of drinking a wine glass of olive oil for breakfast each morning.

Cerebellum – may be involved in developing the human ability to love.194 Plays an important role in the integration of sensory perception and motor output.195 Is intimately connected to the limbic system, the brains emotional control system, and activation of these two systems, e.g. during sport or play, is the reason for the feeling of exhilaration.11 A lack thereof, especially for infants, results in somatosensory deprivation, and an inadequate wiring of the pathways between these the cerebellum-limbic system.196

Medial preoptic area – an area that is essential to maternal behavior.180 DHEA excites this area and promotes active and pleasurable sexual behavior and reactions.128

Vomeronasal organ (VMO) – a small region in the nasal cavity that is believed to be the organ through which human pheromones act.197

Related facts
The following are related facts:

Major histocompatibility complex (MCH) – is a large genomic region or gene family that plays an important role in the immune system, autoimmunity, and reproductive success, i.e. women are found to be vomeronasally-attracted to men with a more dissimilar complex.198 Proteins encoded by it are expressed on the surface of cells and display antigens, i.e. fragments of molecules from invading microbes or dysfunctional cells, such as tumor cells, to a particular type of white blood cell called a T cell that has the capacity to kill or co-ordinate the killing of the microbe, infected cell, or malfunctioning cell.198

| → Sweaty T-shirt study

Pheromones – are sexual signals transmitted from one individual to another through scent, i.e. ‘smell-prints’, which are derived from DHEA.128 Convey information about what species type and genotype, the general purpose of which is to transmit information about immune system, a mechanism to avoid inbreeding. Females are attracted to males with the least similar genotype, which means they are attracted to males who are the least likely to be related to them.199 Are believed to be the chemo-transmission agent involved in the McClintock effect, where females that live together will tend to regulate their menstrual cycles in unison following the lead of the alpha female.200 Male pheromones tend to regulate, synchronize, and to bring female ovulation cycles into a normal range.201

Androstadienone – is a volatile chemical compounds that has been described as having pheromone-like activities in humans and is a derivative of the sex-hormone testosterone.177 It is a component of male sweat that acts as a chemosignal to women causing their levels of cortisol to rise.177

Androsterone [C19H30O2] – is a is a steroid hormone with weak androgenic activity, i.e. it weakly stimulates or controls the development and maintenance of masculine characteristics and acts as a female pheromone attractor.128 The consumption of large amounts of celery can cause an increase in the production of this hormone in males.202 Some musks, such as Jovan, contains alpha-androsterone.

Seminal fluid – alleviates depressive symptoms in women.203

Pleasure center – stable long-term couples mutually stimulate each other centers in a synergistic manner, conversely un-stable partners have unbalanced pleasure center connections.204 Inadequate wiring to this center during infancy results in a later inability to fully experience love and pleasure.11

Alcohol – a social lubricant.134 It relives anxiety thus allowing the pleasure center to react more freely.134

Follicle-stimulating hormone – males in lovehave decreased levels of.176 In men, it enhances the production of androgen-binding protein by the Sertoli cells of the testes and is critical for spermatogenesis.

Tactile stimulation – minimal levels of tactile stimuli deprivation during the stage of active cell growth in infancy results in reduced neural metabolism, reduced dendritic growth, and atrophy of neuron-nourishing glial cells.205

Midcycle – the period of ovulation, during which testosterone, increasing the female sex drive, and estrogen, increasing her femaleness, levels both spike.128

Paramenstruum period – begins about three days prior to the onset of menstruation and lasts about four days into menstruation. It is estimated that approximately sixty-two percent of violent crimes committed by women are committed in this period.11 In this period, estradiol levels fall to fifty percent of baseline, while testosteroneremains relatively high at eighty-two percent of baseline.11

Squalene [C30H50] – a pheromone repellant; stops male courtship behavior in snakes.128

References
1. Neurochemistry (definition) – Dictionary.com.
2. Siegel, George J.; Albers, R.W., Brady, S.T., Price, D.L. (2006). Basic Neurochemistry, 7th Ed.. Academic Press.
3. Thims, Libb. (2007). Human Chemistry (Volume Two) (§12: “Bond History and Neurochemistry”, §§: Neurochemistry, pgs. 503-13). Morrisville, NC: LuLu.
4. Greene, Joshua. (2013). Moral Tribes: Emotion, Reason, and the Gap Between Us and Them (pg. 54). Penguin.
5. Author. (2017). Forbes 100th Anniversary Issue (pg. 78), Nov.

External links
Neurochemistry – Wikipedia.
Empathy (Valerio Loi) – DesignInspiration.net.

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