PreBotzinger Circuit in Respiratory Rhythm Generation

There is increasing evidence that an essential component of the rhythm generating circuitry is located within adiscrete region of the ventrolateral medulla termed the preB6tzinger complex. Nevertheless, an understandingof the preB6tzinger contribution to breathing awaits a comprehensive description of the pertinent propertiesand network interactions of the constituent neurons. The goal of this project to provide a reasonably completedescription of the respiratory neuron types present in the preB6tzinger complex, including their dischargepatterns, response to activation of selected afferent inputs, neurotransmitter (GABA, glutamate, glycine)content and pattern of synaptic connections formed with other preB6tzinger neurons. Given the small size ofthe preB6tzinger complex (in the adult rat it is approximately 0.6 mm long and about 1.5 mm in diameter,including dendrites), it is within our means to provide this analysis. Three Specific Aims will be undertaken.In Aiml, intracellular or extracellular recording will be used to classify neurons with respect to dischargepattern and their response to stimulation of vagus and superior laryngeal nerve afferents. The recordedneurons will then be injected with dye. Subsequent immunohistochemical analysis at the light andultrastructural levels will identify the neurotransmitter content (GABA, glycine, glutamate) and their axonalprojection patterns. In Aim 2, synaptic interactions between preB6tzinger neurons will be identified withcomplementary electrophysiological and anatomical approaches. In the electrophysiological approach, eitherspike triggered averaging or cross-correlation approaches will be used with paired neuronal recordings. Inanatomical experiments intra- or juxtacellular labeling will be used to dye-label cells in 2 different functionalgroups for subsequent light and ultrastructural analysis of their synaptic interactions. In Aim 3, we willdevelop a detailed computational model of the preB6tzinger respiratory network