The morphometric study of the amygdala in the rabbit

Volumetric measurements of the individual nuclei in the amygdala (CA) of the rabbit reveal poor development of the basolateral (BL) and lateral olfactory tract (NLOT) and medial (ME) nuclei. On the other hand, the volumes of the lateral (LA), basomedial (BM), central (CE) and cortical (CO) nuclei are remarkable in this species. A comparison of the densities of neurons in the individual nuclei with the mean numerical density of cells in the rabbit CA indicates that the densities of neurons in LA, BL and BM are significantly lower than the mean (p < 0.05), whereas in CE, CO, ME and NLOT these values are significantly higher than the mean (p < 0.05). It should be noted, however, that of all the nuclei studied those in CE show the greatest similarity in density to CA as a whole. To some extent a similar division of the rabbit CA may be made using the size parameters of the amygdaloid neurons as a marker. The large neurons populate less densely organised CA areas such as LA, BL and BM, whereas the small cells create ME and NLOT, where the neurons are densely arranged. The CE and CO occupy intermediate positions, with the neurons similar in size to the mean for the total rabbit CA. These morphometric data from CA in the rabbit, when compared with the similar data for the common shrew and guinea pig (see our previous papers), lead to the conclusion that the amygdalae in all three species are very similar with respect to the distribution of neurons in relation to density and size and that, when volumetric measurements are taken into account, CA in the rabbit is much more similar to that of the guinea pig than that of the common shrew.