Young mouse blood rejuvenates old brains

Young blood rejuvenates old brains 
Nature Medicine 20, 582–583 (2014)

Villeda et al. show that young blood contains a factor that reverses some aspects of age-related cognitive impairment in mice. Parabiosis in which aged mice are conjoined with aged mice such that their circulatory systems are connected results in no change in synaptic plasticity.
However, parabiois between aged and young mice results in increased expression of proteins involved in synaptic plasticity, and an increased number of dendritic spines and synaptic plasticity in aged mice, as measured by enhanced long-term potentiation in these mice.