Chemistry of love

We previously talked about chemical nature of our biology and how the peptide receptor networks cater for everyday communication requirements of biology. This network forms the very basis of our sense and respond network in order to tackle the threats and avail the opportunities that we come across as we navigate our environment. It is these molecular tweets that mediate answering basic question of biology; the prey, predator and mate conundrum is solved by messaging made possible by these molecular tweets.

These messages not only make us feel good but have profound impact on our health and wellbeing as individuals as well as the families, groups, clans, races and species we count ourselves being part of. The factors that contribute to success at individual level also promote biological fitness and well being of species as a whole. Because the Individual who feel more directed, motivated, and vibrant contribute more to fitness of species as compared to ones who feel stressed, sluggish, and out-of-control. A degree of cooperation is essential among individuals in a species. Species need individuals who cooperate in the group, are not only passionate and committed but feel connected, empathetic and compassionate.

Moreover to be successful individuals have to fall in love, give birth to the young ones, provide care and nurture the young ones and help them succeed in this endeavour for generations to come. All these behavioral expressions are very well regulated by right molecular balance under the hoods and is mediated by various hormones, peptides and neurotransmitters.

So where do we start, the chemistry of love and family. I think in order to avoid a chicken and egg situation we can probably start with the chicken, so lets start with the mother.

So what makes the mother?
In the molecular world of biology, the single molecule that stands out to be mother is Oxytocin. Oxytocin is what makes a mother.

In order to be a mother we need to fall in love first. Chemistry of love is highly complicated. It is orchestrated by several molecules. Oxytocin, Vasopressin, Dopamine, Serotonin, Endorphins, nor-epinephrine, estrogen, testosterone, phenylethylamine.

The ground for chemistry of love is laid in puberty. Puberty is initiated by signals from the brain to the gonads. Gonads respond to the signals that produce hormones to stimulate body and mind to get ready for the adulthood. Two hormones; Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) work in conjunction with each other to trigger the onset of puberty and do all the groundwork along with testosterone in males and estrogen in females.

So, once the stage is set, it is time for ready…set…go…

The template of love seem to be embedded somewhere in limbic and subconscious areas of the brain. It all seems to start with the first tweet, that is encoded by molecule phenethylamine.

That hexagonal structure above with a long handle is phenethylamine (PHE). Structurally phenylethylamine (PEA) is very similar to amphetamine ( shown below).

PEA is a neuromodulator,PEA is a sign of onset of love, romantic love is related to production of PEA but so is eating chocolates. PEA acts in the same way as amphetamine, it is responsible for release two more substances, dopamine and norepinephrine.

It is ok to look at these funny looking structures and it is equally fascinating to watch the similarity between these structures, but how do we actually fall in love is a million dollar question that no one seem to have any answer for.

People who have fallen in love often say it just clicks with the right individual at the right moment but no one seem to be consciously aware of what actually happens under the hoods, so may be falling in love with someone or something is out of our conscious control.

This makes it even more difficult to understand because no one really knows how our subconscious self works. That is probably one of the reason why we say love is blind. But how do right people just happen to bump into each other. Nature’s matchmaking service also has a molecular basis.

Pheromones are set of chemicals that are used in communication between individuals of same species to trigger a specific reaction in the group including but not limited to mating signals. Various small, volatile molecules including proteins, and peptides perform such function. Pheromones are secreted using various mechanisms. Pheromone markers in urine and feces are widely used as territorial marks in many animal species. Sex specific pheromones have also been observed to modulate mother-infant interaction, territorial marking, reproductive synchrony, and sexual attraction in many species.

Interesting enough despite years of research scientists are yet to find any conclusive evidence of pheromone modulating sexuality in humans. There are reports of reproductive synchrony and increase in testosterone levels of males when accompanied by ovulating females but exact mechanisms are still unknown.

It is quite possible that such things are operating at a subconscious level, or it may be our social layers have grown too thick to allow such a rudimentary mechanisms to bubble on to the surface.

Whatever the mechanism be sure, there is an element of physical attraction, coupled with infatuation and subdued lust that underlies romantic love. These elements are mediated by testosterone in both males and females. I think love being an element of higher order social function must sit somehow on top of the biology of lust and if there is any such thing as neural correlates of love they must be manifesting in the subconscious before it becomes apparent to the conscious self.

My hunch is on mirror neurons, A mirror neuron is a neuron that fires both when an animal acts and when the animal observes the same action being performed by another animal. While doing research on monkeys scientists discovered existence of such neurons in premotor cortex area in the frontal lobe of monkey brain. These neurons became active both when the monkeys performed a given action and when they observed a similar action performed by the experimenter.

Much of our learning is achieved by recognition of actions as well as phonetic gestures and if mirror neurons are firing by just watching others do something they are really priming our neural circuits. I speculate if there is such thing as a love circuits in the brain, when two individuals end up firing love circuit together they will end up wiring them together as well, wiring not just in their individual brains but wiring brains of their partners as well. That is why when like minded people participate in activities together they end up falling in love more quickly than people who have diverse interests. Moreover it is not just applicable to romantic relationships alone, friendships and other relationships among otherwise non related individuals also seem to be triggered in similar ways. That is probably the reason why relationships where minds are wired together end up lasting longer than the ones with bodily attractions mediated by testosterone powered lust.

Ok enough about molecular attraction and falling in love, what happens next is that the molecular machinery is taken over by norepinephrine and dopamine on the ride, it is the interplay of these two neurotransmitter that create the experience of bliss, desire, feeling of intense energy, euphoria and sleeplessness. Dopamine is not only a hormone of pleasure but also linked to motivation and addiction. Nor-epinephrine works in association with epinephrine and drives the autonomic nervous system’s fight-or-flight response it rapidly prepares the body for action by boosting supply of oxygen and glucose to the brain and muscles while suppressing other non-emergency bodily processes like digestion. No wonder why people in love don’t feel much hungry. Scientists have also found that feelings of love lead to a suppression of activity in the areas of the brain controlling critical thought, this may be another reason why love is blind.

Dopamine initiates the release of oxytocin. Oxytocin is produced in the hypothalamus, Oxytocin is a peptide of nine amino acids (cys — tyr — ile — gln — asn — cys — pro — leu — gly — NH2).

It looks bit weird because amino acid cysteine at position 1 is folding on to position 6 by forming the disulphide bond. Oxytocin is secreted into the bloodstream with activation of neurons in the hypothalamus. Its release is also controlled by a positive feedback mechanism where release of the hormone causes an action which stimulates more of its own release. Touching and cuddling promotes oxytocin release that is the reason why it is also called “cuddle hormone”.

Its effect fosters trust, bonding and prepares the participating individuals for long term relationships. This is the glue that binds most human relationships, bonds between couples, bonds between mother and child are all mediated by release of Oxytocin.

It is also the oxytocin that triggers uterine contractions to initiate birth sequence. It also releases the milk in mothers to start nursing the young ones. That is how nature takes care of nutritional requirements of the young ones within minutes they are born.

Serotonin ( as shown below) is primarily found in the gastrointestinal tract it is also believed to be a contributor to feelings of well-being and happiness. It promotes warm feelings, relaxation, togetherness and contentment, it is the one that fills the thoughts of beloved in the head.

Once honeymoon period is over it is the endorphins, the feel good neuropeptide, that restore the calmness and lay the foundation for long term relationships. The relations are further strengthened by vasopressin that plays a key role in establishing long term relationships. Vasopressin is also found to induce the protective nature in fathers for jos partner and child.

What is evident here is that after all the chemistry of love is not as simple as it sounds and it may not be easy to reduce the complexities of the behavioural sequence of lust-> Attraction-> Attachment into discrete actions of the underlying molecules of love. Neither it is possible to mix these chemicals in right amounts to create perfect love.

But it is at least feels good to know that this touchy feely thing that seems so elusive is not orchestrated in heavens, after all it has an underlying material substrate. What seem to empower this great circle of life is the properties of the matter mediated by fundamental forces operating at molecular level, but the magic is not in the matter, it is in the script that binds these simple molecules and orchestrates the elaborate interplay.

Originally published at scriptgrandeur.wordpress.com on April 12, 2015.