A NOVEL METHODOLOGICAL APPROACH TO STUDY FUNCTIONAL SEXUAL DIMORPHISM

We present a quantitative study of variations in the number of argyrop hilic nucleolar organiser regions (NORs) in neurons from mamillary bod ies (MBs) and tuberomamillaly nucleus (TM) of the adult rat. This stud y quantifies the NORs of the neurons from these regions in the male an d female rats, the latter during two major phases of the estrous cycle (estrus-diestrus). The number of these NORs stained with an argentic impregnation technique (AgNORs) are considered as an index of the glob al protein synthesis activity of the neurons. Our results show for the first time the existence of significant differences between sexes in the parameter percentage of AgNORs in the TM. However, there were no s ignificant sexual dimorphic differences in the MBs, a region that does not show a clear functional dimorphism. These findings suggest that t he parameter percentage of AgNORs per neuron could be used as a simple index of sexual differences regarding the overall neuronal protein sy nthesis and therefore as an indicator of functional sexual dimorphism.