Preemptive effect of nucleus of the solitary tract stimulation on amygdaloid kindling in freely moving cats.

PURPOSE: The nucleus of the solitary tract (NTS) is a primary site where vagal afferents terminate. The aim of this study was to analyze the preemptive effect of NTS electrical stimulation on daily amygdaloid kindling (AK) in freely moving cats. METHODS: Seven adult male cats were used. Bipolar electrodes were stereotaxically implanted into both amygdalae, lateral geniculate bodies, hippocampi, and prefrontal cortices. In addition, a bipolar stainless steel electrode was implanted in the left NTS. Cats were recorded under the following experimental conditions: The NTS was stimulated for 6 days before the initiation of AK (1 min on/5 min off, 1 h total). AK was performed by stimulating the amygdala every 24 h (1 s, 60 Hz, 1 ms) until behavioral stage VI was reached. RESULTS: The number of stimulations to reach stage VI in control animals was 23.4 +/- 3.7, in lateral tegmental field (LTF) animals was 17.0 +/- 2.1 days. Animals subjected to preemptive NTS stimulation showed a significant increase (53.8 +/- 5.9). In addition, behavioral development was retarded, with an increase in the number of stimulations required to reach stage III. In this group, overall kindling development was delayed, and amygdaloid afterdischarge duration did not show a progressive increase as was observed in the control group. DISCUSSION: Our results indicate that preemptive NTS electrical stimulation interferes with epileptogenesis. This anticonvulsive effect could be related to the activation of certain structures that inhibit seizure development. Therefore, results suggest that NTS mediates the anticonvulsive effect of vagus nerve stimulation.