Ragin' Cajuns, aka. people with hyperekplexia

My mother's family is from New Orleans, and having a zillion cuzzins down in da bayou, I've often heard the term "ragin' Cajuns" but I didn't know its origin until now.

According to Bear et al. (2007), hyperekplexia is an inherited disorder also known as startle disease. It has affected several communities around the world, and was first documented in the late 1870's in Canada.

What is this condition? Everyone jumps sometimes, startled now and then by a loud noise or something we weren't expecting. Apparently, individuals with hyperekplexia disorder, are not only easily startled, but they jump excessively - sometimes even falling to the ground - and cannot help but to jump again (and again!) each time the loud noise or event occurs. In most of us, our nerve cells take steps to help us to deal more evenly with the situation and after a first startle we aren't likely to have another jump (unless you're making your way through a Haunted House!?)

The technical stuff:

Neurotransmitters are chemicals that are passed between some of your nerve cells - both in the brain and the spinal cord - in a way that is kind of like the game of "telephone." In sum, they help determine whether your brain or spinal cord leads another part of your brain or body to take action or not to take action.

Inhibitory neurotransmitters lesson the likelihood of the action because they inhibit or can act upon the excitatory situations. Bear et al. (2007) gives the example that when someone taps on your shoulder and you aren't expecting it, you might jump at first. But if they do it again soon after, you likely won't react with the same jump because you're more "used to it" now. What is really happening is that this reflex is just now being inhibited.

For "Ragin' Cajuns" and others that suffer from this disease, the equipment that helps your body "get used to" startles is built slightly incorrectly due to a gene defect. This equipment is called neurotransmitter receptors. The receptors are like a keyhole that sits in a lock. They are designed to receive a specific "key" - in this case, the inhibitory chemical is glycine. Like a key, it should fit perfectly into the receptor. BUT, if the receptors are even slightly mis-shapen (in fact only one tiny protein out of 400+ is wrong!) the glycine is no longer recognized. Just as if a key and a lock don't match, you don't get in, and if the glycine doesn't match with the receptor because the receptor is misshapen, the inhibiting can't happen.

Here's why:

Usually, in your spinal cord or brain stem, glycine (the key) should activate the glycine receptor (the lock). Once this door is unlocked, it is Chloride that needs to be able to enter. When Chloride is allowed into the cell, it has an effect that calms the cell down. If your cells are "feeling excited" because you've just been spooked, if glycine can get its buddy Chloride onto the scene, in essence, the cell chills out and feels less excited.

(More technically, because Chloride is a negatively charged ion, it causes the charge inside the cell to become more negative, resulting in a more hyperpolarized state. The opposite of this situation, or depolarization is what is needed for a cell to fire an action potential. (In other words for a cell to tell the next one that something exciting is happening.)

Soooooo,

In hyperkeplexia disease, not enough Chloride is getting in to hyperpolarize (calm down) the muscle cells. For this reason, the cells stay more potentially active, and result in dramatic reflexes for the person afflicted...doz Rajun Cajuns!

Bear et al. (2007) mentions that luckily there are drugs today that can help increase the inhibition in these cells, and help people with this problem.

So now, how bout sum gumbo, ya'll?


Resource:
Bear, M.F., Connors, B.W., Paradiso, M.A., (2007). Neuroscience: exploring the brain. New York: Lippincott Williams & Wilkins.