Cortical plasticity

Spinal cord injury immediately changes the state of the brain Aguilar, J. et al. J. Neurosci. 30, 7528–7537 (2010)

Spinal cord injury causes long-term reorganization of the cerebral cortex, but the initial stages of this process are unknown. The authors show that, within minutes of spinal cord transection, cortical responses to sensory stimuli above the lesion site are increased and correlate with slower and altered spontaneous activity of cortical networks. Pharmacologically blocking spinal cord conduction yields similar results. Therefore, spinal cord injury may change the state of cortical networks within minutes and initiate cortical reorganization.

Development

Frizzled-5, a receptor for the synaptic organizer Wnt7a, regulates activity-mediated synaptogenesis Sahores, M. et al. Development 137, 2215–2225 (2010)

Wnt7a is a key factor in synaptogenesis, but its receptor remains unknown. Here, the authors show that Frizzled 5 (Fz5) colocalizes with synaptic sites during synaptogenesis in the mouse hippocampus. Neuronal expression of Fz5 during the early stages of synaptogenesis increases the number of presynaptic sites. Furthermore, neuronal activity increases synaptic levels of Fz5. By contrast, a soluble Fz5 fragment (Fz5-CRD) that binds to Wnt7a and blocks the synaptogenic effect of Wnt7a abolishes high-frequency stimulus-induced synapse formation. These results show that Fz5 acts as the Wnt7a receptor in synaptogenesis.

Neurotransmission

Neurexins physically and functionally interact with GABAA receptors Zhang, C. et al. Neuron 66, 403–416 (2010)

Neurexins are presynaptic cell adhesion molecules that induce synaptogenesis by interacting with neuroligins. Here, neurexin overexpression in cultured neurons downregulated GABAergic synaptic transmission through a neuroligin-independent mechanism. Neurexins exerted these effects by physically interacting with postsynaptic GABAAα1 receptors. These findings suggest a novel role for neurexins in regulating the balance between excitatory and inhibitory transmission, and may help to explain the link between mutations in neurexin genes and cognitive disorders such as autism and schizophrenia.

Chemical senses

The vomeronasal organ mediates interspecies defensive behaviors through detection of protein pheromone homologs Papes, F. et al. Cell 141, 692–703 (2010)

Many animals have the innate ability to recognize chemosignals from potential predators (kairomones), but the underlying neural mechanisms are unknown. By measuring fear response in mice, the authors have identified potential kairomones from rats and cats. The molecules belong to the major urinary protein family and are detected by the mouse vomeronasal organ. These results suggest that mice have evolved a general predator-sensing circuit that includes the vomeronasal organ, which is also used for intraspecies chemical communication.