Further reading
延伸閱讀
And
yet, this delectable, universally loved
treat is bad news for man’s best friend. Dog owners
are warned to be particularly careful with stashing
away their chocolate, out of reach and out of sight
from their furry companions. Accidental ingestion
could cause an upset stomach at best, and be
lethal at worst.
Chocolate’s popularity is not only attributed
to its luscious sugary taste, but also to its active
compounds, namely, theobromine and caffeine
from cacao [1]. These two compounds are known to
promote the release of dopamine in human brains.
Also known as the “feel-good” hormone, dopamine
serves a critical role in the brain’s pleasure-reward
system as a neurotransmitter. It is also believed to
be the culprit for addictive behaviours such as drug
or gambling addictions.
The source of concern is the mechanism by
which theobromine and caffeine achieve this
stimulating ef fect. Theobromine is a pr imar y
metabolite of caffeine. Both chemical structures
of theobromine and caffeine resemble that of a
neurotransmitter called adenosine. Thus, they can
potentially block adenosine’s action by binding to
and inhibiting the function of adenosine receptors.
This blockade is a problem because adenosine’s
job is to promote drowsiness and prevent the
brain from accumulating an excess of dopamine.
When adenosine activity is diminished through
compet it i ve i nh ibit ion, the ner vous sys tem
becomes hyperactive, causing an increase in
heart rate and blood pressure. Depending on
how you see it, this increase could be a good
thing since it promotes alertness. However, too
much of these chemicals can cause the jitters, as
any overworked student who just downed three
shots of espresso can testify.
Due to a difference in levels of tolerance, the
effects of chocolate on dogs are much more
pronounced. I n humans, the l ethal dose 50
(LD
50
), which is toxicology jargon for “the dose
at which 50% of the population will be killed by
the chemical”, is 1,000 mg/kg of theobromine [2].
Theoretically, the heavier the subject, the more of
the drug they can tolerate. Not only are dogs much
By Raphaella So
蘇韋霖
“There is nothing better than a friend, unless it is a friend
with chocolate”.
– Linda Grayson
This article may be useful as supplementary
reading for biology classes, based on the DSE
syllabus.
根據生物科文憑試課程綱要，本文或可作為有用的補
充讀物。
Why is Chocolate
Toxic for
Dogs?
為什麼狗
不能吃朱古力？
