The kindling of motor seizures from hippocampal commissure in the rat

The hippocampal commissure was stimulated in 35 rats in order to find conditions which favor triggering of motor seizures on the first trial. Strain and supplier of rats, size and orientation of electrodes, distance between electrode poles, area of the commissure stimulated, ongoing behavior, pattern of electrical activity in the hippocampus, and state of arousal were varied. In each case, motor seizures developed only after many daily stimulations, as reported for other limbic sites. However, stimulation of corpus callosum or cingulum yielded motor seizures on the first trial. It is concluded that previous reports of first-trial motor seizures triggered from the hippocampal commissure (Racine et al., 1972) must have resulted from stimulation which encroached upon these more dorsal structures. The results suggest that kindling may not be restricted to the strengthening of limbic-limbic connections but may also require modification of circuits lying more distal to the limbic system.