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Neurons in the lamprey spinal cord can sense pH and counteract changes from the body’s optimal range.
September 1, 2016|
NOBEL INSTITUTE FOR NEUROPHYSIOLOGY, ELHAM JALALVAND
E. Jalalvand et al., “The spinal cord has an intrinsic system for the control of pH,” Curr Biol, 26:1346-51, 2016.
Bodies like to keep their pH close to 7.4, whether that means hyperventilating to make the blood alkaline, or burning energy, shifting to anaerobic metabolism, and producing lactate to make the blood acidic. The lungs and kidneys can regulate pH changes systemically, but they may not act quickly on a local scale. Because even small pH changes can dramatically affect the nervous system, a study led by Sten Grillner of Karolinska Institute in Sweden looked for a mechanism for pH homeostasis in the spinal cord.
Using the lamprey as a model system, the researchers observed that a type of spinal canal neuron, called CSF-c, fired more rapidly when they bathed it with high pH (7.7) or low pH (7.1) media. They could suspend the elevated activity by blocking two ion channels: PKD2L1 channels, which stimulate neurons in alkaline conditions, or ASIC3 channels, which, the team showed previously, do the same in acidic states.
As the neurons fired, they released the hormone somatostatin, which inhibited the lamprey’s locomotor network. These results suggest that, whichever direction pH deviates, “the response of the system is just to reduce activity as much as possible,” Grillner says. The pH-regulating role of CSF-c neurons is likely conserved among animals, the authors suspect, given the presence of these neurons across vertebrate taxa.
“It’s an interesting finding because it adds a level of regulation to maintain homeostasis in the central nervous system,” says Pierre Magistretti of King Abdullah University of Science and Technology in Saudi Arabia who was not involved in the work.