PROJECTION FROM NUCLEUS REUNIENS THALAMI TO PIRIFORM CORTEX - A TRACING STUDY IN THE RAT

To study the cells of origin and area of termination of the projection from the nucleus reuniens thalami (NRe) to the piriform cortex (PC) w e used anterograde and retrograde tracing with the B subunit of the ch olera toxin, Tracer injections in the NRe resulted in anterogradely la beled fibers in the dorsolateral part of the PC layers I and III, Foll owing injections in the PC, retrogradely labeled cells were observed p rimarily in the dorsal subdivision of the NRe. Moreover, a topographic al organization was observed in this subdivision: its anterior part pr ojects to the posterior part of the PC, whereas its middle part projec ts to the anterior part of the PC, The present findings suggest that t he NRe may exert different modulatory influences on the dorsolateral p art of both anterior and posterior PC areas. The possible role of the NRe in the olfactory information processing is discussed.