Increased robustness and adaptation to simultaneous temperature and elevated extracellular potassium in the pyloric rhythm of the crab, .

Animals must deal with numerous perturbations, oftentimes concurrently. In this study, we examine the effects of two perturbations, high extracellular potassium and elevated temperature, on the resilience of the pyloric rhythm of the crab, . At control temperatures (11°C), high potassium saline (2.5× K) depolarizes the neurons of the stomatogastric ganglion (STG), and the pyloric rhythm becomes quiescent. Over minutes, while remaining depolarized in high potassium, the pyloric network neurons adapt, and resume their spiking and bursting activity. We compared adaptation to high potassium applications at 20°C to those seen at 11°C. At 20°C, the intracellular waveforms of the neuronal activity seen in high potassium more closely resemble activity in control saline, and adaptation and recovery occur more rapidly. Spike and burst thresholds were measured using slow ramps of injected current from hyperpolarized to depolarized values of membrane potential in the presence of high potassium and at both temperatures. The maximal burst frequencies in control saline were higher at 20°C and subthreshold bursts occurred at a more hyperpolarized membrane potential at 20°C. In high potassium, subthreshold bursts were seen at 20°C, but not at 11°C, whereas spike thresholds were similar at the two temperatures. At both temperatures, a second application of high potassium showed substantially more rapid adaptation than did the first application. Together, these data show that the adaptation to high potassium saline is enhanced by high temperature. Multiple applications of high potassium saline to the pyloric rhythm of the crab, show a history-dependent adaptation process that is enhanced at high temperatures.