Influence of long‐term facilitation on timing, amplitude, and inspiratory neural network complexity in urethane‐anesthetized P20‐21 neonatal Sprague Dawley rats

Abstract

Long‐term facilitation (LTF) is a form of respiratory plasticity, which is expressed as a persistent increase in inspiratory motor output following intermittent, but not continuous, hypoxia. We have recently begun to examine LTF‐related changes in the timing, magnitude, and inspiratory neural network complexity (quantified by approximate entropy ApEn analysis) in neonatal (ages P12‐P18) rats. Our previous work has revealed that respiratory LTF is characterized by an enhancement of burst frequency due to reductions in both TI and TE (except in P12 rats), an increase or no change in burst amplitude, and an age‐dependent modulation in ApEn, such that ApEn values were reduced in P12‐P13 rats and increased in P14‐ P18 rats; the peak responses occurred at = 50 min in P12‐P13 rats and at = 45 min in P14‐ P18 rats. The LTF‐related changes in older neonatal rats remain to be identified. Therefore, we examined these features during LTF in 7 spontaneously breathing urethane‐anesthetized P20‐21 rats. In this case, respiratory LTF was characterized by an increase in burst frequency, an ~10‐20% decrease in burst amplitude, and variable effects on ApEn, such that ApEn values were decreased in P20 rats and increased in P21 rats. Regardless, the peak changes in ApEn values were noted at ~40 min for both age groups. Our findings suggest that respiratory LTF‐related changes are developmentally regulated. Supported by NS045321 and NS049310