Social isolation slows functional recovery and worsens cell damage after stroke in young animals, primarily by increasing the body’s inflammatory response. Changes occur in the inflammatory response with age, so it was unknown if isolation would induce the same detrimental effects in aged mice. Researchers examined whether social isolation interfered with short- or long-term recovery in aged male mice and whether being housed in pairs would reverse those effects.
Male 18-month-old mice were pair-housed for two weeks before undergoing an experimentally induced stroke (middle cerebral artery was occluded for 60 minutes) or a sham surgery with no cut-off in circulation to the brain. Afterwards, the animals were housed alone or in pairs.
After 72 hours, mice isolated after stroke had larger volume of dead brain tissue and more severe neurological impairment than those housed in pairs. Levels of interleukin 6, an inflammatory substance produced in response to injury, were higher in mice isolated after a stroke compared with pair-housed mice that had stroke or sham surgery; levels were similar by four weeks post-stroke.
Paired animals performed better than isolated mice on an object recognition test and had greater expression of a growth factor that promotes cell proliferation and reduces inflammation after stroke (brain-derived neurotrophic factor), and had higher levels of brain white matter protein (myelin basic protein).
Abstract W MP88
Rajkumar Verma, Ph.D., University of Connecticut Health Center, Farmington, Conneticut.