Where might these specific EP3 receptors be located?
And it seems like they are located most prominently in
the anterior and preoptic areas of the hypothalamus.
And why these are important or these are important for
responding to temperature changes such as heat,
responding to temperature changes such as cold.
So whether you’re responding to heat and sweating
or cold and shivering, these are the specific hypothalamic
nuclei that we are wanting most concern about.
So the neurons in the preoptic anterior hypothalamus
seemed to be the ones that are most prominent
to undergo heat retention mechanisms, such as shivering,
and heat dissipation mechanisms, such as sweating.
So now, these prostaglandin E2 molecules can
stimulate EP3 receptors in these preoptic
anterior hypothalamic neurons and these will
induce the fever response.
So now, we want to compare fever to other
types of hyperthermia.
To do that, we are going to compare and contrast fever
versus exercise, because I think these provides us a
nice mechanism by which we can look at the differences
between increasing internal temperature
via two different mechanisms.
So both fever and exercise increase internal body
temperature. And we all know that, we all have a
fever at one point, and we’ve all done a little
exercise at one point or work.
We know, that both of those that increase our body temperature.
But they do it in to dramatically different ways.
So let’s look at fever first. Fever increases body temperature
by first increasing the temperature set point.
So as soon as your response into either a bacteria
such as LPS, you will then have a cytokine response,
that cytokine response then goes via a prostaglandin E2
to an EP3 receptor on a preoptic anterior hypothalamic
neuron and that increases the temperature set point.
That drives there to be an increase to body temperature
by things like shivering, causing vasoconstriction,
ways to minimize body heat loss. By doing all those
items, you start to increase your body temperature.
Exercise, is almost the exact opposite. Body temperature
increases but your body is trying to cool itself.
So during exercise, you’re sweating, you are vasodilating
your skin, you are definitely not shivering.
What you are trying to do is loss heat. And even though
you are trying to loss heat, body temperature gradually
raises because you’re producing more heat than
you are losing it.
Comparing that with fever again, there is a change in
the set point and that drives up in the internal temperature
versus a heat stress whether be exercising induced.
Usually there is an increase in an internal temperature
because of an increase of metabolism, even though
set points stays flat.