MONDAY, Dec. 19 (HealthDay News) -- Mice with a mutation in the methyl-CpG-binding protein 2 (MECP2) gene have less norepinephrine and serotonin as well as drastically fewer tyrosine hydroxylase neurons in their medullas, according to a study in the Dec. 14 issue of the Journal of Neuroscience. The finding sheds light on Rett syndrome, a severe neurological condition seen in one in 10,000 children, mostly females, that is characterized by mental retardation and respiratory problems.
Jan-Marino Ramirez, Ph.D., of the University of Chicago in Illinois, and colleagues generated male mice lacking MECP2, a gene mutation associated with Rett syndrome, and compared them with normal littermates.
While the Mecp2-deficient mice had normal breathing at birth, their respiratory rhythm progressively worsened and the mice died of respiratory arrest at about two months of age. The researchers found that the medullas of the mice had considerably less norepinephrine and serotonin, as well as drastically fewer tyrosine hydroxylase neurons than normal mice. In vitro experiments suggested that exogenous norepinephrine could stabilize the respiratory network.
"We hypothesize that breathing disturbances in [male Mecp2-deficient] mice, and probably Rett patients, originate in part from a deficiency in noradrenergic and serotonergic modulation of the medullary respiratory network," the authors conclude.
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