Reciprocal connections between medial prefrontal cortex and lateral posterior nucleus in rats

The connections of the posterior part of the medial prefrontal cortex with the thalamic lateral posterior nucleus in rats were studied using anterograde and retrograde axonal transport of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) and tritiated leucine. After injections of WGA-HRP into the medial prefrontal cortex, an area confirmed to receive direct projections from the visual cortex, retrogradely labeled neurons were observed ipsilaterally in the lateral posterior nucleus of the thalamus, as well as in the mediodorsal, anteromedial, ventromedial, ventrolateral, laterodorsal, centrolateral, paracentral, rhomboid, parafascicular and posterior nuclei. In the lateral posterior nucleus, the labeled cells were located mainly in the lateroventral portion of its anterior half. In contrast, the posterior half of this nucleus was free of label. Axons labeled by the anterograde transport of tritiated leucine were dispersed over the same region which contained retrogradely labeled cells. The functional significance of these connections is discussed with special reference to their possible role in visuomotor integration in rats.