Predictions and experimental tests of a new biophysical model of the mammalian respiratory oscillator

Previously our computational modeling studies (Phillips et al., 2019) proposed that neuronal persistent sodium current (I-NaP) and calcium-activated non-selective cation current (I-CAN) are key biophysical factors that, respectively, generate inspiratory rhythm and burst pattern in the mammalian preBotzinger complex (preBotC) respiratory oscillator isolated in vitro. Here, we experimentally tested and confirmed three predictions of the model from new simulations concerning the roles of I-NaP and I-CAN: (1) I-NaP and I-CAN blockade have opposite effects on the relationship between network excitability and preBotC rhythmic activity; (2) I-NaP is essential for preBotC rhythmogenesis; and (3) I-CAN is essential for generating the amplitude of rhythmic output but not rhythm generation. These predictions were confirmed via optogenetic manipulations of preBotC network excitability during graded I-NaP or I-CAN blockade by pharmacological manipulations in slices in vitro containing the rhythmically active preBotC from the medulla oblongata of neonatal mice. Our results support and advance the hypothesis that I-NaP and I-CAN mechanistically underlie rhythm and inspiratory burst pattern generation, respectively, in the isolated preBotC.