Functional sexual dimorphism of the nucleolar organizer regions in the tuberomamillary nucleus

The tuberomamillary nucleus (TM) is a cluster of magnocellular neurons that are located close to the mamillary recess or basal surface of the mamillary body (MBs) and is the only known source of histamine (HA). The nucleolar organizer regions (NORs) of the nervous cells of the subnuclei E1, E2 and E3 of the TM are quantified in this paper to discern the existence of possible sexual differences in the overall neuronal protein synthesis between male and female rats in two phases of the oestrous cycle (oestrous-dioestrous). We have used the argentic impregnation technique of the NORs (AgNORs) in both bilateral nuclei of the TM and found functional bilateral symmetry in its AgNORs. Furthermore, we demonstrate the existence of significant differences (P < 0.001) between sexes and between two phases of the oestrous cycle studied (oestrous-dioestrous) in the parameter of number of AgNORs per neuron. Hormonal manipulation of the TM in the rat during the two periods, postnatal or adult, shows the importance of the activational effect of the hormones on the activity of cellular protein synthesis.