Respiratory modulation of sympathetic nerve activity is enhanced in male rat offspring following uteroplacental insufficiency

• Modulation of sympathetic nerve activity in phase with the respiratory cycle is prominent.
• Amplified respiratory modulation of sympathetic activity is observed in a number of models of hypertension prior to the development of increased blood pressure.
• Male rats exposed to uteroplacental insufficiency have increased blood pressure by 6 months of age.
• Using the working heart–brainstem preparation we tested whether these rats display altered respiratory modulation of sympathetic nerve activity at 35 days of age.
• Respiratory parameters were not altered in the uteroplacental insufficiency rats.
• Respiratory-modulated bursts of sympathetic activity were larger and the Traube–Hering waves amplitude were increased.
• These rats displayed increased peripheral chemoreceptor sensitivity.
• Amplified respiratory modulation of sympathetic activity may play a role in the development of hypertension in this model.

Sympathetic nerve activity to the cardiovascular system displays prominent respiratory-related modulation which leads to the generation of rhythmic oscillations in blood pressure called Traube–Hering waves. An amplification of this respiratory modulation of sympathetic activity is observed in hypertension of both genetic, the spontaneously hypertensive rat, and induced, chronic intermittent hypoxia or maternal protein restriction during gestation, origin. Male offspring of mothers with uteroplacental insufficiency, induced by bilateral uterine vessel ligation at 18 days of gestation, are also hypertensive in adulthood. In this study we examined whether these male offspring display altered respiratory modulation of sympathetic activity at pre-hypertensive ages compared to controls. Respiratory, cardiovascular and sympathetic parameters were examined using the working heart–brainstem preparation in 35 day old male rats that had reduced birth weight due to uteroplacental insufficiency. Whilst all respiratory parameters were not different between groups, we observed an enhanced respiratory-related burst of thoracic sympathetic nerve activity and amplified Traube–Hering waves in the growth-restricted group. This group also showed an increased sympathetic and bradycardic response to activation of peripheral chemoreceptors. The observations add support to the view that altered respiratory modulation of sympathetic activity represents a common mechanism involved in the development of several forms of hypertension.