Claustrocingulate connections in the rabbit and rat--a stereological study

Unbiased stereological methods were used for estimating the numerical density and the total number of claustral neurones projecting to the cingulate cortex in rabbit and rat. In rat the numerical density of neurones projecting to the retrosplenial granular cortex (RSG) differed significantly from those projecting to the retrosplenial agranular (RSA) and cingulate (Cg) cortices while in rabbit the numerical densities of retrogradely labelled neurones in the claustrum following injections into various areas of the cerebral cortex did not differ significantly. The total number of retrogradely labelled neurones in the claustral limbic zones did not differ significantly in both species. The quantitative analysis of claustral zones projecting to a different cingulate cortex area, both in rabbit and rat, reveals that each of these zones is rather homogeneous.