RESUMO
Projections from cingulate cortex area 3(Cg3) to the subcortical nuclei in the rat were examined by using phaseolus vulgaris leucoagglutinin (PHA-L) immunohistochemical anterograde tracing method. The projecting topography showed rostrocaudally as follows: accumbens, medial 1/3 part of caudate-putamen, bed nucleus of stria terminalis, lateral preoptic area, paratenial thalamic nucleus, anteromedial thalamic nucleus, mediodorsal thalamic nucleus, anterior paraventricular thalamic nucleus, reticular thalamic nucleus, lateral habenular nucleus, posterior paraventricular thalamic nucleus, parafascicular thalamic nucleus and ethmoid thalamic nucleus etc. Beneath the thalamus, labeled fibers were densely distributed in zona incerta, the medial edge of internal capsule and the area surrounding mammillothalamic tract. From the areas mentioned above, fibers also projected into lateral hypothalamic area. The present paper paid a special attention to the distribution of the labeled fibers of amygdala. In amygdala, labeled fibers were converged in the anterior nucleus of basolateral nucleus and the ventromedial nucleus of lateral nucleus and thus it was confirmed that the Cg3 cortex projections took part in the "basolateral-limbic circuit", the so called "memory circuit". However, in the central nucleus of amygdala sparse labeled fibers could only be found occasionally. In view of this fact, we did not consider that the Cg3 cortex took part in the "visceral circuit". Labeled fibers from the injection side passed through the genu of corpus callosum to the contralateral hemisphere, and the projection topography was basically similar to but less dense than that of the injection side.