Do anatomical axes and physiologic activity correlate in rat endopiriform nucleus and claustrum?

The endopiriform nucleus and claustrum are brain regions that are anatomically and functionally situated between the insular cortex and subcortical structures such as striatum. Subregions of these structures have been defined with various anatomical tracing methods and suggest a crude topographic relation of subregions with neocortical or subcortical (thalamic) areas. We studied endopiriform and claustral cells staining and morphology in male Sprague Dawley rats. The patterns of dendritic branching by cells suggest an alternative view of the overall orientation of these brain regions. The main dendritic branches of these predominantly bipolar neurons tend to run in a rostro‐dorsal to caudo‐ventral axis, angled off the horizontal plane. Fewer dendrites extended in the plane orthogonal to this axis. We have followed the same planes of section in our electrophysiological studies of field potentials in acute brain slices. We find that anatomical and physiological data are consistent with segregation of activity along the angled rostro‐caudal axis described above and suggest a basis for integrating inputs to and distributing the output of endopiriform nucleus and claustrum. Grant Funding Source : Multiple Sponsors