Cell Type-Dependent Activation Sequence During Rhythmic Bursting in the PreBotzinger Complex in Respiratory Rhythmic Slices From Mice

Spontaneous respiratory rhythmic burst activity can be preserved in the preBotzinger Complex (preBotC) of rodent medullary transverse slices. It is known, that the activation sequence of inspiratory neurons in the preBotC stochastically varies from cycle to cycle. To test whether the activation timing of an inspiratory neuron depends on its neurotransmitter, we performed calcium imaging of preBotC neurons using double-transgenic mice expressing EGFP in GlyT2(+) neurons and tdTomato in GAD65(+) neurons. Five types of inspiratory neurons were identified using the fluorescence protein expression and the maximum cross-correlation coefficient between neuronal calcium fluctuation and field potential. Regarding the activation sequence, irregular type putative excitatory (GlyT2(-)/GAD65(-)) neurons and irregular type glycinergic (GlyT2(+)/GAD65(-)) neurons tended to be activated early, while regular type putative excitatory neurons, regular type glycinergic neurons tended to be activated later. In conclusion, the different cell types define a general framework for the stochastically changing activation sequence of inspiratory neurons in the preBotC.