American bullfrogs, Lithobates catesbeianus, are air-breathing ecothermic vertebrates that use both pulmonary and cutaneous gas exchange to meet their metabolic needs. Elevated metabolic rates at warm temperatures require pulmonary ventilation for O2 acquisition and CO2 elimination in frogs. At temperatures below ~5°C metabolism is reduced such that cutaneous gas exchange should be sufficient to sustain aerobic metabolism. As a result, lung ventilation diminishes in the cold. American bullfrogs overwinter for 3-5 months (depending on latitude and location) significantly decreasing activity of the respiratory control system that drives lung ventilation for an extended period. In fact, overwintering in aquatic habitats covered with ice (e.g., frozen ponds) completely prevents aerial respiration. In the spring, water temperatures can rise rapidly (Tattersall & Ultsch, 2008) and cutaneous gas exchange will no longer be sufficient to sustain metabolically expensive spring behaviors such as calling. The system that controls lung ventilation that has been quiescent must function properly to match both metabolic demands for O2 and for CO2 elimination requirements. How does the respiratory control system that drives lung ventilation resume operation following months of disuse and work at near maximal levels? Given the importance of central chemosensing for ventilatory control of acid-base balance, we addressed this question by investigating how cold-acclimation alters cellular CO2/pH sensitivity. The locus coeruleus is a chemoreceptive brain region that contributes to control of pulmonary ventilation of anuran amphibians in vivo (Noronha de Souza et al., 2006). We assessed chemosensitivity of locus coeruleus neurons using whole-cell patch clamp electrophysiology (methods described in Santin et al., 2013) from bullfrogs acclimated to either ~22°C or ~2°C for two months. We determined that chemosensitive locus coeruleus neurons from cold-acclimated bullfrogs had reduced sensitivity to hypercapnia [increase from 1.3% CO2 (normocapnia) to 5% CO2 (hypercapnia); cold-acclimated: 92±29% (n=13) vs. control: 221±41% (n=7); p=0.025; two-tailed unpaired t test]. We showed that 86% (30/35) of neurons had chemosensitive responses (Santin et al., 2013); however, only 54% (7/13) of locus coeruleus neurons from cold-acclimated frogs exhibited CO2/pH-sensitive firing rates (p=0.0002; Fisher exact test). Baseline firing rates did not differ between control and cold-acclimated animals (p=0.70; two-tailed unpaired t test), suggesting that normocapnic excitability is unaltered by cold-acclimation. These results provide evidence that critical components of the respiratory control system that regulate lung breathing (e.g. neuronal chemosensitivity) are maintained, although at a reduced capacity, despite several months of reliance on cutaneous gas exchange. Maintenance of central or peripheral components of the respiratory control system in the near or complete absence of lung breathing may be essential for temperate frogs to resume breathing sufficiently to meet metabolic demands upon warming in the spring after overwintering. Understanding how overwintering frogs switch from extended use of exclusively cutaneous gas exchange to pulmonary ventilation will provide new insights into robustness of the respiratory system that controls lung breathing.