Effects of scopolamine on the rewarding and seizure-inducing properties of amygdaloid stimulation.

The relationship between amygdaloid brain-stimulation reward and the evolution of seizure activity was evaluated in this study. Current levels that maintained optimal intracranial self-stimulation (ICSS) rates were found to be lower than the minimal current intensity required to elicit an afterdischarge (AD) from the central nucleus of the amygdala. After the ICSS session, AD thresholds (ADTs) were reduced to the same levels of current used to support ICSS. Assessment of seizure stage development during ICSS testing revealed that the emergence of early-stage epileptiform events following repeated amygdaloid stimulation suppressed ICSS performance. While administration of the antimuscarinic scopolamine did not prevent the stimulation-elicited reduction in AD thresholds, it was observed to inhibit seizure progression and increase ICSS rates. These results are consistent with the excitatory function of acetylcholine in epileptogenesis and were related to the possibility that different mechanisms underlie the rewarding and seizure-inducing properties of amygdaloid stimulation.