Hibernation improves neural performance during energy stress in regions across the central nervous system in the American bullfrog

Abstract

Neuronal signaling requires high rates of ATP production via the oxidative metabolism of glucose. The American bullfrog is intriguing, as this species has typical brain energy requirements for an average vertebrate but modifies synaptic physiology and metabolism after hibernation to maintain function during hypoxia and ischemia. Given the importance of the respiratory system in restoring metabolic homeostasis during emergence from underwater hibernation, work to date has addressed this response in the brainstem respiratory network. Thus, metabolic plasticity has been interpreted as an adaptation used to restart respiratory motor behavior under hypoxic conditions during the transition from skin breathing to air breathing. It remains unclear whether these improvements are specific to the brainstem regions critical for breathing versus a global response within the central nervous system (CNS). To address this question, we recorded neural activity from the spinal cord, forebrain, and brainstem respiratory network in vitro. As expected, hypoxia disrupted the function of each network in control animals. After hibernation, each network improved its activity in hypoxia compared to controls. These results suggest that plasticity that improves neural function during energy stress following hibernation reflects a global response that may impact many behaviors controlled by the CNS and is not limited to regions involved in metabolic homeostasis.