Effects of acute hypoxia and hyperoxia on ventilation in spontaneously hypertensive and normotensive rat.

The aim of this study was to investigate whether there are differences between particular characteristics of the ventilatory responses to acute hypoxia and hyperoxia in primary hypertensive and normotensive states which might indicate significant differences in arterial chemoreceptor reflex function. Pneumotachographic monitoring of ventilation was carried out in anesthetized, spontaneously breathing, normotensive randomly bred Wistar rats (NWR), Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). Under air breathing conditions, minute ventilation in SHR (50 +/- 2 ml/min per 100 g) was not significantly different from that of WKY (54 +/- 3 ml/min per 100 g) but NWR had a significantly lower minute ventilation (39 +/- 1 ml/min per 100 g) than both SHR and WKY. Our data indicate that there is no elevation of the ventilatory drive under air breathing conditions which can be unequivocally associated with primary hypertension in adult animals. During acute hypoxia, minute ventilation increased by a similar magnitude in SHR and NWR (by 97 and 77%, respectively, above baseline values), whereas in WKY the increase was only 58%. When exposed to acute hyperoxia, minute ventilation was inhibited by a similar degree in all animals investigated. We conclude that there is no characteristic pattern of peripheral chemoreceptor-mediated ventilatory responses in close association with primary hypertension.