Persistence of reorganized synaptic connectivity in the amygdala of kindled rats

Kindling stimulation was applied to the basolateral amygdala of adult rats, and the density of dendritic synapses was examined under the electron microscope in the medial amygdaloid nucleus (MAN) contralateral to the site of stimulation, and an unfolding correction of biasedness was made. When generalized motor seizures had been induced for 5 days consecutively, the kindling was considered to be complete. The number of dendritic synapses, but not the number of somatic synapses, was markedly decreased in the MAN of the kindled rats. Reductions in numbers were marked in the case of both dendritic shaft and spine synapses. The reductions in numbers of shaft and spine synapses were similarly evident in the MAN of kindled rats 100 days after stimulation was discontinued. The numbers of dendritic synapses were similarly decreased in the rats that received additional bouts of stimulation subsequent to the completion of kindling. Thus, once the kindling was completed, the newly acquired synaptic connectivity was preserved in the MAN. These findings indicate that the remodeling of synaptic connectivity was a morphological correlate of the kindling in the MAN.