Effects of long-term raphe nucleus stimulation on chronic limbic seizures in monkeys.

Long-term electrical stimulation of the raphe nuclei was performed in two monkeys with chronic psychomotor seizures. The daily seizure rate was significantly reduced in one monkey when a stimulus charge of 0.1 microC was used, but not during a subsequent experiment using a 0.4 microC charge. A charge of 0.4 microC also failed to alter the frequency of limbic seizures in a second monkey. The raphe stimulation caused neural damage to the brain stems of both animals. The possible effect this damage may have had on the repeatability of the results suggests that long-term raphe stimulation, like some other neural prostheses, may have diminishing effectiveness over time.