Do genes on rat chromosomes 9, 13, 16, 18, and 20 contribute to regulation of breathing?

Abstract As part of a large scale, high through-put physiologic genomics study, we sought to determine whether genes on rat chromosomes 9, 13, 16, 18, and 20 contribute to phenotypic differences in the control of breathing between two inbred rat strains (SS/Mcw and BN/Mcw). Through a chromosomal substitution breeding strategy, we created 5 consomic rat strains (SS.BN9, SS.BN13, SS.BN16, SS.BN18, and SS.BN20), which were BN/Mcw homozygous at only one chromosome and SS/Mcw homozygous at all other chromosomes. Standard plethsmography was used to assess eupneic breathing and ventilatory responses to CO 2 (F i CO 2 =0.07) and hypoxia (F i CO 2 =0.12), and Pa CO 2 during treadmill exercises provided the index of the exercise hyperpnea. There were no robust differences in eupneic breathing between any strains. The ventilatory response to CO 2 was 150% greater ( P P P P 2 sensitivity is not due to genotypic differences on the 5 chromosomes studied to date, but genotypic differences on chromosomes 9 and 18 contribute to differences in ventilatory responses to hypoxia, exercise, and/or to the differences in the PSA.