Regional brain IR-Met-, IR-Leu-enkephalin concentrations during progress and full electrical amygdaloid kindling

Using amygdaloid kindling in chronic rats, we were able to observe behavioral, electrographic and IR-Met- and IR-Leu-enkephalin changes throughout the progress of different stages of convulsive activity. Rats presenting the initial stages of kindling, rats presenting the first generalized motor seizure, and rats with at least 10 generalized seizures were sacrificed 24 h after the last stimulus; also rats with at least 10 generalized seizures but sacrificed 21 days after the last seizure were compared with control and sham-operated groups of rats. The IR-Met and IR-Leu enkephalin concentrations in each group were measured in the striatum, amygdala, hypothalamus, medulla oblongata (including pons), hippocampus, mid-brain, spinal cord and cerebral cortex. A progressive increase in IR-Leu-enkephalin in amygdala and hippocampus was observed over the course of kindling. These increases remained until 21 days after rats were fully kindled (at least 10 generalized seizures). We observed increased and decreased concentration of each peptide in different regions. We discussed the regional and the differential effects of each peptide. The increased concentrations in limbic structures were associated with the amygdaloid increased excitability through the kindling process. We suggest that the decreases in concentrations are related with structures involved in the output behavior manifestations produced by kindling stimulation.