Abstract

Exogenous oxytocin (OXY) administration has been shown to enhance parasympathetic drive. Previous research has demonstrated that vagal control is pivotal in exercise performance. In our earlier work, we found that during hypobaric hypoxia (HH), there is an impairment of baroreflex-dependent parasympathetic control, which coincides with a deterioration in exercise performance. Therefore, the administration of OXY can improve baroreflex-dependent parasympathetic control, thereby enhancing exercise performance during HH. This study aimed to investigate the impact of OXY administration on exercise performance and cardiovagal control in rats during HH. Male adult Wistar Kyoto rats (n=8, 2765g) were randomly assigned to Vehicle (Veh, n=4) and OXY groups (n=4). Veh (NaCl 0.9%, 100L, i.p.) and OXY (0.433g/kg, 100L, i.p.) were administrated for 14 days. Before and after Veh and OXY, the animals underwent an incremental exercise performance test (J) during normobaric normoxia (NN, pO2:156mmHg) and HH (pO2:100mmHg). After 14 days, baroreflex (bolus technique) was assessed during NN and HH, and ventilatory response HH was determined. Before Veh or OXY administration, the two groups had no significant difference in exercise performance during HH. However, the OXY group demonstrated a similar work done between NN and HH (382.260.2 vs. 281.5105.6 J, respectively), a response not observed in the Veh group (353.7104.5 vs. 73.21.4 J, respectively). The Veh group showed a baroreflex reset (blood pressure 50: 26.88.9 mmHg) and an increment of bradycardic response (parasympathetic indicator) (54.924.3 beats/min) during HH, which was reversed with OXY administration (blood pressure 50: -37.08.8 mmHg; bradycardic response: -54.620.8 beats/min). Both groups showed similar ventilatory responses to HH (60% minute ventilation). Our results strongly indicate that the administration of exogenous OXY significantly improved the vagal response to HH and was associated with an enhanced exercise response during HH.