pH Detectors in Lamprey Spinal Cords Control Cell and Locomotor Activity

Neurons in the lamprey spinal cord can sense pH and counteract changes from the body’s optimal range.

Alison F. Takemura
Aug 31, 2016

NEUTRALIZERS: Cells in the lamprey spinal cord have PKD2L1 receptors (pink) that detect alkaline pH and produce somatostatin (green) to lower it. NOBEL INSTITUTE FOR NEUROPHYSIOLOGY, ELHAM JALALVAND


The paper
E. Jalalvand et al., “The spinal cord has an intrinsic system for the control of pH,” Curr Biol, 26:1346-51, 2016.

pH swings
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.

Channeling change
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.

Break time
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.

Local control
“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.