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Morphological Properties of Brainstem Excitatory and Inhibitory Neurons Controlling Breathing in Mammals

Fang Cao, Joseph Nugent, Ruli Zhang, Naohiro Koshiya, Hidehiko Koizumi, and Jeffrey C. Smith

Cellular and Systems Neurobiology Section, NINDS, NIH

Breathing in mammals is the primal homeostatic process regulating oxygen and carbon dioxide levels that are crucial for life. Rhythmic breathing movements are generated and exquisitely regulated by central nervous system circuits. While it has been known for over a century that the critical neural machinery resides in the brainstem, only recently have the precise locations of the essential microcircuits been identified. One such microcircuit resides within the pre-Bötzinger complex (pre-BötC), a highly circumscribed area of the ventral medulla that is the site for respiratory rhythm generation. The structural and functional architecture of pre-BötC circuits, essential to understanding rhythm generation, has not been determined. In this project we combined techniques for high-resolution structural-functional imaging, molecular assays, and automated 3D morphometric reconstruction of these circuit neurons. Specifically, we have completely reconstructed somatodendritic morphologies of 28 functionally and molecularly identified rodent pre-BötC respiratory neurons (16 excitatory, 12 inhibitory), including excitatory neurons with pacemaker-like autorhythmic properties. Our morphometric reconstructions reveal dendritic aborizations with remarkably planar arrangements, and distinct differences between inhibitory and excitatory neurons including axonal projection patterns that reflect the rhythmogenic function of the pre-BötC.  These results contribute significantly to the reconstruction and overall understanding of pre-BötC circuits.

Last updated December 14, 2012