Ventilatory Responses to Hypoxia and Hypercapnea in Young, Middle Aged and Old Male and Female Rats

• Published in: The FASEB journal 2007, Vol.21 (6), p.A1293-A1293
• Main Authors: Wenninger, Julie M., Cotter, Caitlin J, Olson, E. Burt, Thomas, Cathy F, Behan, Mary
• Format: Article
• Language: English
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fasebj.21.6.A1293-a

What little is known about effects of gender and age on respiratory control is confusing. Moreover, sex hormone levels and arterial blood gas levels during ventilatory responses are rarely measured. We measured ventilation, arterial blood gases and sex hormone levels in awake male and female rats at 3 ages (young, Y, 3mo; middle aged, MA, 12mo; old, O, 20mo). One week after femoral arterial catheterization, rats were placed in a flow‐through plethysmograph and acclimated in room air (40 min). Rats were exposed (10 min) to hypoxia (Hx, 12% O2), normoxia (Nx), and hypercapnea (7% CO2). Arterial blood was drawn during the last 3 min of acclimation and each gas exposure and at the end of the study. We see age‐associated changes in some ventilatory responses. While minute ventilation (VE) during Nx or Hx did not differ between Y and MA males or females, during exposure to CO2, Y males and females increased VE compared to their MA counterparts. In Y females, both frequency and tidal volume (VT) increased, while in Y males only VT increased. There were no ventilatory differences between males and females of the same age (Y, MA). As testosterone level decreased with age in male rats and progesterone to estrogen ratio changed with age in female rats, these data support the hypothesis that age‐associated changes in sex hormone levels influence ventilatory responses. Supported by NIH AG18760 (MB) and the Parker B. Francis Foundation (JW)