Previously, we reported the existence of renin-expressing neurons in the nucleus ambiguus (NuAm), a major autonomic and respiratory center in the brainstem. Within the NuAm, renin is expressed in choline acetyltransferase (ChAT)-positive cardioinhibitory vagal neurons projecting to the cardiac ganglion. Based on this, we hypothesized that ablation of renin specifically in ChAT-positive neurons disrupts normal cardiorespiratory function. Cardiorespiratory function in control (WT) vs. mice lacking renin in cholinergic neurons (Ren-a ChAT-null ) was compared using an integrated radiotelemetry/whole-body plethysmography system. We measured parameters at baseline and upon acute respiratory or pharmacological challenge in males. Using in situ mRNA hybridization, we confirmed that Ren-a ChAT-null exhibit lower expression of renin in the NuAm compared to the WT (Ren-a ChAT-null : 0.7±0.3 vs. WT: 3.9±0.9 arbitrary units, p<0.05, n=4-5). At baseline, there were no major differences in cardiorespiratory function between groups. Therefore, mice were subjected to acute cardiorespiratory challenges. During acute hypoxia (12% O 2 for 10 minutes), Ren-a ChAT-null displayed lower hypoxic ventilatory response compared to WT (1.53±0.04 vs. 1.94±0.10 fold change compared to baseline, p<0.05, n=4). Additionally, Ren-a ChAT-null exhibited exacerbated tachycardia (640±19 vs. 564±11 bpm, p<0.05, n=3-4). Subsequently, when subjected to sympathetic blockade with propranolol (5 mg/kg, ip), Ren-a ChAT-null exhibited an exacerbated bradycardic and hypotensive effect compared to WT (14427±293 vs 15722±498 AUC bpm*min, p<0.05, n=7-9 and 3661±90 vs 3988±78 AUC mmHg*min, p<0.05, n=7-9, respectively). In response to parasympathetic blockade with methyl atropine (2 mg/kg, ip), Ren-a ChAT-null exhibited a lower systolic blood pressure elevation compared to WT (4001±112 vs. 4324±84 AUC mmHg*min, p<0.05; n=7-9). These data suggest that renin in cholinergic neurons exerts a functional physiological role and contributes to maintaining an appropriate cardiorespiratory response to acute stressors. Ongoing studies are currently underway to investigate 1) sex differences and 2) the phenotype of Ren-a ChAT-null mice in chronic conditions such as hypertension.