Bjork - Many people with anorexia nervosa will have a lowered seizure threshold, whether they take Wellbutrin (bupropion) or not. The reason for the lower seizure threshold is not fully understood, but if I had to hazard a guess, I'd say that it may be due to an electrolyte imbalance brought on by vomitting &/or diarrhea.

When one vomits excessively, or has bouts of protracted diarrhea, and is not adequately rehydrated with electrolytes (esp. potassium, sodium, etc.) this can affect the transmission of electrical impulse along (and between) nerves. The electrical signal that is carried along axons (the long part of the nerve cell that makes connections to the next nerve cell) is a result of an eletrical charge difference between the inside of the nerve cell and the outside of the nerve cell. The inside of a nerve cell is slightly negatively charged relative to the outside.

This electrical gradient is maintained by sodium-ion pumps imbedded in the axon membrane. The sodium-ion pump moves the positively-charged sodium ions out of the nerve cell. Proteins inside the nerve cell are negatively charged. Thus, the interior of a nerve cell, when at rest, is negatively charged, relative to the exterior of that neuron.

An electrical signal travels the length of an axon and when it reaches the end of one axon, neurotransmitters are released into the (synaptic) gap between two neurons. If the electrical signal is strong enough, a sufficient amount of neurotransmitter is released causing the next neuron to "fire" and the electrical signal is propagated (ie. travels) along the axon of that nerve cell.

It is the above mentioned electrical gradient across a neuronal membrane that allows an electrical signal to travel along the axon toward the next neuron. How this is accomplished is as follows. As an electrical signal( called and "action potential") moves along the neuronal membrane (ie. the nerve's cell wall) the "electricity" causes normally closed sodium-ion channels that span the width of the neuronal membrane to open briefly. Sodium ions flood into the nerve cell by diffusion. The high concentration of sodium ions outside the cell pour into the cell where there is a low concentration of sodium ions, due to the action of the sodium-ion pump, which normally keeps sodium ions out of the neuron.

This causes a flip-flop of polarity of the electrical gradient of the across the neuronal membrane. The outside of the nerve cell is now slightly negavtively charged, relative to the inside. This flip-flopping of charges lasts only a fraction of a second and the sodium-ion channels slam shut, stopping the sodium ions from moving into the cell. The sodium-ion pumps again move the sodium ions back out of the cell.

Here is an animation of the movement of an electrial signal along a nerve cell's axon, whic is also called "Propagation of an Action Potential" .

For a more scientific explanation of an electrical signal travelling along a nerve cell, see: "Action Potential" .

Perhaps an Overview of the Human Nervous System may help.

BTW: Na+ is a sodium ion and K+ is a potassium ion. The potassium ions act as a buffer to smooth out the transition between positive and negative states during the "flip-flop" of polarity between the inside and outside of the nerve cell.

Anyway, back to anorexia nervosa and lowered seizure threshold. With vomitting &/or diarrhea the body loses significant amounts of sodium ions and potassium ions (as well as other important electrolytes). This can interfere with the above propagation of action potentions, and the nerve cells cannot carry electrical signals from one neuron to the next as efficiently as they should. When this happens, the neuron can spasm or cut off signals that are supposed to be transmitted to other nerve cells. This interuption of electrical power supply, especially when it occurs in the temporal lobes, may result in seizure activity (similar to the seizures seen in temporal lobe epilepsy, but the ultimate causes are probably different). This may be how seizure threshold is lowered in people suffering from anorexia nervosa (at least in part; there are probably other mechanisms causing a disruption of action potential propagation).

Wellbutrin also lowers the threshold at which seizures occur. The additive effect of the two mechanisms may have caused the "nasty Grand Mal Seizure" that you experienced. Over the past year you may not have had the right (...er, wrong) combination of variables that would trigger a seizure. This time all the variables fell into place and "bingo", down you went. I am sure that there were a number of other variables involved outside of electrolyte imbalance and a Wellbutrin side effect, but my knowledge of the causes of seizures is limited.

I do hope that this is of some help. I know that the above is complicated, but I tried to simplify the whole process as best I could. The links that I provided may be able to clear up the murkiest parts of my attempted explanation. Then again, my whole hypothesis may be wrong.

I'd like to hear from Larry and T_MD (and anyone else with a little knowledge of physiology) to see if I am on the right track with my hypothesis. I'm old and it's hard to remember this stuff. I learned this over 20 years ago, and some of the details may have been updated. - Cam