EN
The aim of this study was to recognize the sex differences in the architecture of the medial gastrocnemius (MG) motor nucleus in the same age rats. The retrogradely labeled motoneurons in the MG motor nucleus were studied following a bath of proximal stump of the transected MG nerve in the horseradish peroxidase. The rostrocaudal distribution of motoneurons along the spinal cord and on transversal sections as well as size and density of motoneurons in the motor nucleus were determined from serial microscopic images. It was shown that length of the motor nucleus in L4–L6 segments was 37% greater in males. Three types of motoneurons with different soma diameter were revealed: α one (27.5–40.0 μm), α two (greater than 40.0 μm) and γ (smaller than 27.5 μm). The density of α one and α two motoneurons was 15% higher in females. However, sex differences between the number of α one and α two motoneurons were more significant in group of α one motoneurons. The number of α one motoneurons in the motor nucleus was 24% higher in males than females (41 versus 33 motoneurons). The density of α motoneurons was 31% higher in females. It is concluded that length of the MG motor nucleus is greater in males, but the density of α and γ motoneurons was higher in females.