Morphometric analysis of the neuronal numbers and densities of the inferior olivary complex in the donkey (Equus asinus)

The morphometric interrelations between the compartments of the inferior olivary complex (IOC) in the donkey (Equus asinus) were ascertained by examining serial sections throughout the entire length of the IOC for both sides. Nissl-stained celloidin sections of four brainstems of donkeys were used. The IOC consisted of three major nuclei and four small cell groups. The total neuronal count in both sides of the IOC was 202,040 ± 8480 cells. The medial accessory olivary nucleus (MAO) had the largest relative area (46%) and the highest number of neurons (90,800 ± 7600). The dorsal accessory olivary nucleus (DAO) had the second largest relative area (33%), while the principal olivary nucleus (PO) had the lowest relative area (21%). However, the total neuron count in the PO was larger (60,840 ± 1840) than DAO (50,360 ± 4040). The average neuronal density was 2700 ± 400 cells/mm3. The numerical values of the current study of the IOC in the donkey were similar to those of other mammals.