Figure 4.

Autonomously active neurons are part of the spectrum of intrinsic building blocks responsible for rhythmic population bursts in the preBötC. At the cellular level, a diversity of mechanisms exist to produce several forms of bursting that have different pharmacological properties. Some neurons express cadmium-insensitive bursting (CI) that is riluzole sensitive, and therefore, appears to be mediated by I_NaP (blue). Other neurons express cadmium-sensitive bursting (CS), predominantly mediated by both voltage-dependent Ca²⁺ currents (Ca_v) and a FFA-sensitive I_CAN. Moreover, pharmacological blockade of 5HT2A receptors can turn CI-bursting into tonic spiking while activation of a1-noradrenergic receptors in tonic spiking neurons into CS-bursting. This type of conditional bursting demonstrates that the role of autonomously active neurons in the preBötC may not be fixed. Hence, while both forms of bursting, CI and CS, depend on dominant current(s) to drive spontaneous bursting, all putative inspiratory neurons of the preBötC appear to possess tonic boosting currents (grey), the I_NaP (blue), I_CAN (yellow), and Ca_v (purple).