SCIENCE & TECHNOLOGY
LIMITED PARTNERSHIP Latest findings CONTRADICT HYPOTHESIS that calcium signaling enables glial cells to influence synaptic activity
2nd International Symposium on
DNA-Encoded Chemical function, concerns have been raised as to tritional support to neurons in the brain. whether such ‘gliotransmission’ is merely Many neuroscientists believe that glial an experimental artifact,” Kirchhoff writes. cells also influence neuronal function at For this reason, research associate Censynapses through calcium-dependent dra Agulhon and pharmacology professor release of chemical messengers known as Ken D. McCarthy at the University of gliotransmitters, thereby affecting learning North Carolina, Chapel Hill, used new exand memory. Several studies bolster this perimental methods for the latest study. contention, but research just published in Science calls it into question (2010, 327, THE RESEARCHERS developed two lines 1250). of genetically modified mice in which Regardless of which hypothesis proves receptor-mediated calcium release was correct, researchers agree that neurons either prevented or could be stimulated and glial cells have a working relationship. on command in astrocytes. Electrical Presynaptic neurons activity assays and release neurotransfluorescent imaging of mitters that bind not brain slices from the only to receptors on genetically modified postsynaptic neurons mice showed these but also to receptors changes had no effect on adjacent astrocytes, on synaptic activity or a type of glial cell. This plasticity. binding liberates calThe data indicate cium stored in the asthat calcium signaltrocytes’ endoplasmic ing is not sufficient to reticulum, explains trigger gliotransmisFrank Kirchhoff, a sion by astrocytes, neuroscientist at Max Agulhon says, “so we Planck Institute of Exhave to reconsider perimental Medicine, what has been claimed in Göttingen, Germaso far about the role of ny, in an accompanyastrocyte calcium exing commentary (Scicitability in synaptic ence 2010, 327, 1212). PARTNERS Astrocytes (shown in red in activity and plasticthis fluorescent micrograph) mingle Prior studies have ity.” But she adds that with neurons (blue) in the brain, suggested that the “even though our data but it’s debatable whether calcium freed calcium stimushow that astrocyte signaling helps astrocytes shape lates astrocytes to recalcium signaling is neuronal activity. lease serine, glutamate, not involved in release and adenosine triphosof gliotransmitters, phate, which serve as astrocytes are still gliotransmitters that affect synaptic activpartners of neurons for many other physiity. These studies relied on pharmacologiological functions.” cal approaches, such as bathing astrocytes Agulhon acknowledges that the new in compounds that activate their calcium findings will be controversial, so she next receptors, to manipulate calcium levels in plans to use two-photon imaging to study the cells. interactions between astrocytes and neu“Although this scenario may well exrons following sensory stimulation in livplain how astrocytes directly affect neuron ing animals.—SOPHIE ROVNER © K. KASISCHKE & P. FISHER/CORNELL U
GLIAL CELLS provide structural and nu-
WWW.CEN-ONLINE.ORG
57
MARCH 15, 2010
Zurich (Switzerland) 20th August 2010 www.pharma.ethz.ch ponsors:
Undertheauspicesof:
