Low-frequency stimulation

Recently, we became interested in the impact of low-frequency stimulation on the threshold for triggering kindled seizures.

As a backdrop for this interest, many years ago, John Gaito came to my lab to learn the basics of how to kindle rats. After doing several unusual things with his rats (like stimulating them in their grounded steel cages), he tried low-frequency stimulation on them — a procedure we had used routinely as a coulombic control in learning experiments in the '70s. In doing so, he accidentally discovered that such stimulation, interspersed amongst his normal kindling trials, appeared to delay kindling and elevate seizure thresholds. However, in part, because of his minimal kindling history and 'unusual' approach to experimentation, this result was largely ignored.

For other reasons, we have begun to re-examine this effect in more controlled experiments, and, indeed, have found that a moderate intensity (100 microamps) of low frequency stimulation applied for a relatively short duration (30 s) to an amygdala kindled site can raise the local afterdischarge threshold by ~200-300% — an effect that peaks 24 hours later and lasts for 2-3 days! This happy outcome, of course, raises the spectre of a potential positive therapeutic outcome. To achieve this eventuality, however, a positive outcome must also be forthcoming from the testing of many additional parameters and circumstances associated with this demonstration. Several of these parameters are currently under study.