The piriform cortex and the endopiriform nucleus in the rat reveal generally similar pattern of connections.

The afferent and efferent connections of the piriform cortex and the endopiriform nucleus in the rat were studied by the method of axonal transport of two fluorescent tracers: Fluoro-Gold and Fluoro-Ruby. The results indicate that both structures possess not only the connections with the olfactory system, but also the reciprocal connections with the limbic system (entorhinal cortex, amygdaloid body), thalamus (mediodorsal and midline nuclei), extrapyramidal system (ventral part of the nucleus accumbens). The topographic differences in the organization of the association connections between the anterior and posterior parts of the piriform cortex are reported. Additionally, the reciprocal and relatively numerous connections between the endopiriform nucleus and the piriform cortex may result in their modulatory function, which in some pathological circumstances may have a critical significance in epileptogenesis.