Influence of gender and endogenous sex steroids on catecholaminergic structures involved in physiological adaptation to hypoxia
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Abstract Mechanisms underlying sex-related differ ences in adaptation to high altitude were investigated by assessing the turnover of dopamine and noradrenaline in structures of the chemoafferent pathway, i.e. carotid body and brainstem noradrenergic cell groups (A1, A5, A 6, A2 to which chemosensory fibres project). The influ ence of gender was assessed in male and female rats reared at an altitude of 3600 m, whereas the influence of endogenous sex hormones was evaluated by castration. Haematocrit, red blood cell count and plasma erythropoi etin levels were lower in females than in males (–5%, –15%, –53%, respectively). Dopamine and noradrenaline turnover were higher in female structures (carotid body: +51%; A2: +140%; A1: +54%; A5: +27%). Dopamine and noradrenaline turnover in carotid body and brain stem cell groups were differently affected by castration, i.e. enhanced by orchidectomy (carotid body: +134%; A 2: +120%; A1: +69%; A5: +67%) but inhibited by ovar iectomy (carotid body: –33%; A2: –92%). Orchidectomy elicited a reduction in haematocrit (–10%), haemoglobin concentration (–8%) and red blood cell count (–24%), whereas haematological status remained unaltered after ovariectomy. Therefore, both gender and endogenous sex steroids may control catecholamine activity differently in structures involved in the chemoafferent pathway, thus providing a neurochemical basis for sex-related differ ences in adaptation to hypoxia.