The preBotzinger Complex (preBotC) gives rise to two types of breathing behavior: eupnea and sighing. Here, we examine the neural mechanisms that couple their underlying rhythms by recording from the preBotC in neonatal mouse brainstem slice preparations. It has been proposed that chloride-mediated synaptic inhibition couples inspiratory (eupnea-related) bursts and sigh bursts, but we find no evidence to support that notion. First, we characterize a fluctuating temporal relationship between sigh bursts and their preceding inspiratory bursts; their coupling is far weaker than previously described. Surprisingly, selective blockade of inhibitory synapses strengthened (rather than weakened) that phasic inspiratory-sigh burst relationship. Furthermore, pharmacological disinhibition did not alter the duration of the prolonged interval that follows a sigh burst prior to resumption of the inspiratory rhythm. These results demonstrate that coupling between inspiratory and sigh rhythms does not depend on synaptic inhibition.

Role of synaptic inhibition in the coupling of the respiratory rhythms that underlie eupnea and sigh behaviors