Summary:  Purpose: This work analyzed the effect of electrical stimulation of the nucleus of the solitary tract (NTS) on the development of electrical amygdaloid kindling (AK) in freely moving cats.Methods: Nine male adult cats with implanted electrodes in both amygdalae (basolateral nucleus), both lateral geniculate bodies, left NTS, and both prefrontal cortices were used. Electromyogram and electrooculogram also were recorded. The AK was performed every 24 h (1‐s train, 1‐ms pulses, 60 Hz, 300–600 μA). The NTS was stimulated previously for 1 min (0.5‐ms pulses, 30 Hz, 150–300 μA), just before the AK at 10:00 a.m., and then every 60 min, 4 times, from 11:00 a.m. to 2:00 p.m. On different days, all NTS stimulation was suspended, and AK was continued until stage VI kindling was reached.Results: Behavioral changes produced by the stimulation of the NTS were blinking, immobility periods with upward sight, licking, and swallowing. Animals with simultaneous stimulation of NTS and AK did not reach stage VI, remaining in behavioral stages I–III. Stage VI was reached after NTS stimulation was intentionally suspended. The amplitude, duration, and the propagation of the amygdaloid afterdischarge did not exhibit progressive evolution during NTS stimulation. A regression analysis was performed between the number of days with only AK stimulation and days with simultaneous NTS stimulation, which showed a positive correlation (values of r = 0.84).Conclusions: Our results suggest that NTS stimulation interferes with the development of convulsive evolution and secondary generalization. This delay effect may be due to the activation of the locus ceruleus and some areas of the midbrain reticular formation, among other structures, which has been demonstrated to inhibit experimental convulsive seizures.

Young adult heterozygous Lurcher mice constitute an excellent model for studying the role of the cerebellar cortex in motor performance—including the acquisition of new motor abilities—because of the early postnatal degeneration of almost all of their Purkinje and granular cells. Wild-type and Lurcher mice were classically conditioned for eyelid responses using a delay paradigm with or without an electrolytic lesion in the interpositus nucleus. Although the late component of electrically evoked blink reflexes was smaller in amplitude and had a longer latency in Lurcher mice than that in controls, the two groups of animals presented similar acquisition curves for eyeblink conditioning. The lesion of the interpositus nucleus affected both groups of animals equally for the generation of reflex and conditioned eyelid responses. Furthermore, we recorded the multiunitary activity at the red and interpositus nuclei during the same type of associative learning. In both nuclei, the neural firing activity lagged the beginning of the conditioned response (determined by orbicularis oculi muscle response). Although red nucleus neurons and muscle activities presented a clear functional coupling (strong correlation and low asymmetry) across conditioning, the coupling between interpositus neurons and either red nucleus neurons or muscle activities was slightly significant (weak correlation and high asymmetry). Lurcher mice presented a nonlinear coupling (high asymmetry) between red nucleus neurons and muscle activities, with an evident compensatory adjustment in the correlation of firing between interpositus and red nuclei neurons (a coupling with low asymmetry), aimed probably at compensating the absence of cerebellar cortical neurons.

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.