How exactly does the brain control breathing?

An understanding of exactly how the brain controls breathing is fundamental to the treatment of respiratory disorders. We know that breathing is an automatic rhythmic process that persists without conscious effort whether we are awake or asleep, but the question that has intrigued many scientists for well over 100 years is what maintains this almost fail safe vital rhythm throughout life?

Experimental Physiology editor Julian Paton invited two world renowned scientists Dr. Guyenet from the University of Charlottesville and Dr. Richerson from Yale University, to use the journal as a forum to discuss the issue and attempt to resolve their differences in opinion.

Both authors agree that the respiratory rhythm requires specialised nerve cells (central chemoreceptors) to power the rhythm, but the issue highly debated by Guyenet and Richerson is the precise location and cell types involved. Guyenet proposes that these nerve cells are located in a ventral area of the brainstem (the retrofacial region) and loaded with a transmitter substance called glutamate. Their close proximity to the ventral surface of the brain allows them to sense and react to changes in the pH of the cerebrospinal fluid; this is deemed an essential property of a central chemoreceptor. Richerson, on the other hand, stipulates that central chemoreceptors are found close to the midline blood vessels of the brainstem allowing them to 'taste' the pH of the blood. His cells do not contain glutamate but a substance called serotonin.

Experimental Physiology asked each author to stake out his claim and provide rebuttals and critiques of each others' articles (recently published in Nature Neuroscience).

To view this fascinating exchange of views published in Experimental Physiology-

Retrotrapezoid nucleus: a litmus test for the identification of central chemoreceptors
Patrice G. Guyenet, Ruth L. Stornetta, Douglas A. Bayliss and Daniel K. Mulkey
Exp Physiol 90.3, pg.247

Homing in on the specific phenotype(s) of central respiratory chemoreceptors
G. B. Richerson, W. Wang, M. R. Hodges, C. I. Dohle, A. Diez-Sampedro
Exp Physiol 90.3, pg.259

Respiratory control by ventral surface chemoreceptor neurons in rats. Nature Neuroscience, 7(12), 1360-1369. Mulkey, DK, Stornetta, RL, Weston, MC, Simmons, JR, Parker, A, Bayliss, DA & Guyenet, PG (2004).

Midbrain serotonergic neurons are central pH chemoreceptors. Nature Neuroscience. Vol. 6(11), 1139-1140 Severson CA. Wang W. Pieribone VA. Dohle CI. Richerson GB. (2003).

Source : Blackwell Publishing Ltd.