INFLUENCE OF GENDER AND ENDOGENOUS SEX STEROIDS ON CATECHOLAMINERGIC STRUCTURES INVOLVED IN PHYSIOLOGICAL ADAPTATION TO HYPOXIA

Mechanisms underlying sex-related differences in adaptation to high al titude were investigated by assessing the turnover of dopamine and nor adrenaline in structures of the chemoafferent pathway, i.e. carotid bo dy and brainstem noradrenergic cell groups (A(1), A(5), A(6), A(2) to which chemosensory fibres project). The influence of gender was assess ed in male and female rats reared at an altitude of 3600 m, whereas th e influence of endogenous sex hormones was evaluated by castration. Ha ematocrit, red blood cell count and plasma erythropoietin levels were lower in females than in marks (-5%, -15%, -53%, respectively). Dopami ne and noradrenaline turnover were higher in female structures (caroti d body: +51%; A(2): +140%; A(1): +54%; A(5): +27%). Dopamine and norad renaline turnover in carotid body and brainstem cell groups were diffe rently affected by castration, i.e. enhanced by orchidectomy (carotid body: +134%: A(2): +120%; A(1): +69%; A(5): +67%) but inhibited by ova riectomy (carotid body: -33%; A(2): -92%). Orchidectomy elicited a red uction in haematocrit (-10%), haemoglobin concentration (-8%) and red blood cell count (-24%), whereas haematological status remained unalte red after ovariectomy. Therefore, both gender and endogenous sex stero ids may control catecholamine activity differently in structures invol ved in the chemoafferent pathway, thus providing a neurochemical basis for sex-related differences in adaptation to hypoxia.