No human condition has such a wide variety of symptoms. On one hand lies sleeplessness,
irrational behavior, eating disorders, depression, mania, the inability to focus,
and a great deal of pain. On the other stands intense concentration, vigor,
confidence, and what most would consider the ideal state of life. No single
force has contributed more to the shaping of society. Every home, temple, and
countless works of art are built on one feeling, while just as many fires, murders,
suicides, and even wars have stemmed from the same feeling…love.
But what is love, really? Some would say the asking of this question marks
the beginning of humanity itself, and yet society still fails to understand
it fully. Biochemistry may, oddly enough, aid us in answering this very old
question.
The
initial feelings of attraction are heavily associated with the b-phenylethylamine
(PEA) norepinephrine. Norepinephrine triggers the breakdown of glycogen and
triacylglycerols, which provides the body a boost of energy. The stimulant functions
by binding to the surface of liver cells, signaling them to produce cyclic AMP
(cAMP). This molecule then breaks the active parts of protein kinase A (PKA)
away enabling them to alter certain proteins. The exact nature of these proteins,
once altered, is uncertain and currently under investigation. What is not uncertain
is their end result on the human psyche. Clinical studies have found doses of
PEA, which induces the entire cycle, to relieve depression in 60% of patients.
Patients noticed improvements in energy, attention and mood as well. Anyone
smitten could attest to all of these symptoms.
Some drugs appear to inhibit PEA. Lithium, an anti-depressant, blocks the manic
highs associated with the stimulant. Recently lithium has been shown to affect
reactions involving the removal of a phosphorous group, however it is still
unclear exactly how lithium works. Many patients report they are less likely
to be attracted to someone while taking Lithium. It’s a rather strange
concept that a pill or injection can make you less susceptible to infatuation
or love.
Chocolate has long been rumored to promote infatuation as it contains PEA.
However, the digestive system brakes down phenylethylamine. Studies in people
found that eating up to two pounds of chocolate a day causes no increase of
PEA in urine or the blood stream. People in the initial stages of attraction
have increases in both. The fanciful effect noted by chocolate-lovers is a simple
result of extremely large amounts of caffeine and sugar.
Recent studies on monogamy in mammals have focussed on the endorphins, vasopressin
and oxytocin. Endorphins are neuromodulators in that they can effect the rate
at which nerves fire. Oxytocin serves several functions in the body including
control over uterine contractions, cervical softening, and penile erection in
the male. Other oxytocin-receptive nerves act in the modulation of pain as well.
Vasopressin typically is known for action in the cerebral cortex aiding in memory.
These endorphin studies have centered on the vole, a tiny mouse-like rodent
that lives in the Midwest United States. Two species of voles, although similar
in most respects, differ greatly in terms of mating habits. Prairie voles are
extremely monogamous. A pair will share the same burrow-nest, cooperate in raising
young, show distress if separated, and spend most of their lives side by side.
Even if one of the pair dies, the other rarely finds another mate. The counterpart
to the prairie vole is the montane vole. The mountainous rodent is promiscuous,
only maternally parental, and appears to be ambivalent to isolation.
Initial
investigations showed that prairie vole females did not form a bond with a male
until after mating. When the body makes a protein it must first make a portable
copy or transcribe the instructions provided by the DNA encoded gene. This copy
carries the instruction outside of the cell nucleus where it can be turned translated
into a protein. These portable instructions are called messenger RNA (mRNA).
Prairie vole females also showed an increase in oxytocin mRNA after mating.
Such an increase infers that the body is making more of the oxytocin protein.
Montane females showed no such increase. This information led researchers to
believe oxytocin could be the key to their monogamy. Prairie vole females injected
with oxytocin antagonists before mating did not develop any sort of bond with
very hurt and confused males. Females injected with oxytocin developed bonds
with males in their presence in spite of never mating. The same experiments
were conducted in male prairie voles using vasopressin and its antagonist. Males
produced the same results as the females. Montane voles showed no reaction to
the injections, although the male vole increased self-grooming greatly with
the vasopressin injection. Thus, in a species far monogamous than humans, the
source of undying "love" was found to be no more than the release
of a single polypeptide.
Genetic analysis showed that both species of vole posses identical receptors
for oxytocin and vasopressin, leading investigators to believe the difference
was in the placement of the receptors. If an area of the brain contains these
receptors the activity associated with that part of the brain would become stimulatede
if vassopressin or oxytocin were introduced. In the prairie vole, oxytocin receptors
were found in different locations of the brain than the Montane vole. Researchers
have therefore theorized that the section of the brain enabliing monogamy is
present in the area of the brain possessing the receptors of oxytocin and vasopressin
in prairie voles. Researchers have likewise theorized that the area of the brain
containing vasopressin receptors in Montane voles is responsible for grooming
habits. Current research is trying to create transgenic mice that will have
the vole vasopressin receptor, presumably making them monogamous.
....and Now It's Gone, Gone Gone...
One component of love that science may soon be able to explain fully is the
heartache involved with a romantic breakup, which may be a type of withdrawal.
In some addictions the nerves become satiated with certain signals. Cocaine
abuse produces an example of such a withdrawal. Neurotransmitters carry the
signal of a nerve impulse over the synapse or space between nerve cells. Cocaine
blocks these neurotransmitters form being removed from the synapse. This effect
produces a prolonged excited state. To compensate, the nerve cell receiving
the neurotransmitter will reduce the number of receptors it has to prevent over
stimulation. Once cocaine is removed, the nerves will still lack these receptors
and be unable to sense the now reduced signal in the synapse. The body would
then need the drug to function properly and feel a desperate need for the drug.
This could result in a rebound as with alcoholics. When animals addicted to
alcohol in a laboratory setting are deprived for more than 2 days and then allowed
access to alcohol, their consumption significantly increases. People exhibit
this behavior in relationships as well. Examples of this can be seen in any
airport terminal. People don’t greet their loved ones with as much excitement
every day as they do when returning from a long period of separation.
Another phenomenon associated with relationships is the addiction to PEA. The
"rebound" phenomenon is therefore a rush to satisfy a neurological
addiction. Other people tend to go from the initial stages of one relationship
to the next as soon as the temporary effects of PEA begin to wear off. Infatuation
seem to be more responsive to changes in PEA levels as opposed to steady states
of high or low concentrations, which would explain a large amount of indecision
in dating. As mentioned earlier, Lithium may be useful in breaking these cycles
and relieve extreme withdrawal symptoms of love.
All of these findings, although impressive, may seem to take away from the
grandeur of the human heart. Science is consistently challenging humanity to
rush into deciphering morality. It presses upon us the question of how much
we really want to know about the world and ourselves. Early advancements in
the understanding of the solar system’s organization caused fear that God
was being pushed aside or undefined. These present discoveries about our thought
processes evoke the same sense of danger and loss with the soul of mankind itself.
Many fear this type of scientific inquiry is slowly turning our hearts into
biological machinery.
These fears can be addressed. Accurately defining the processes within the
mind may serve to broaden our understanding our relationships and ourselves.
Biochemical understanding of love may provide medical benefits in the treatment
of the potentially negative aspects of love such as obsession, withdrawal and
depression. It may also enable physicians to aid those for whom love does not
seem possible.
If the full biochemical pathway of love is discovered, one’s heart will
drop just as far when holding a newborn child. Looking into the eyes of a loved
one will still produce the greatest magic in the world. Magic is something we
give ourselves, not something the outside world provides us, just as all meaning
in this world comes from the self. Some are disappointed by such a thought,
but that’s truly where the beauty lies. We live in a world where we decide
the meaning. We are, in turn, creators of our own realities and our own happiness.
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