Neocortical projections of the rat anterior commissure

The posterior limb of the rat anterior commissure (ACp) was studied in order to better define a temporal cortex in this species. Two methods were used: (1) the anterior commissure (AC) was destroyed on one side of the midline, and the resulting anterograde degeneration was traced with the Fink-Heimer stain; and (2) the corpus callosum and hippocampal commissure were severed, but the AC was left intact. [3H]-Leucine and proline were injected into one hemisphere, and the transported label was traced into the contralateral hemisphere with autoradiography. ACp was found to project to the contralateral cortex along the rhinal sulcus. The pyriform cortex received a projection along the entire length of the sulcus. There was also a distinct projection to neocortex on the lateral surface above the rhinal sulcus which appears to be analogous to the temporal cortex projection of ACp in other species. This finding of a neocortical projection of the ACp in the rat is consistent with observations that have been made on other mammals.