Post-
stroke systemic
injections of
insulin-like growth factor-1 (IGF-1) exert
neuroprotective effects in rats. In the current study, we aimed to test the efficacy of
IGF-1 neuroprotection in aged rats (24-25 months old) and to compare the results with adult rats (6-7 months old). Furthermore, we addressed putative differences in microglial responses to
IGF-1 in adult and aged rats. Rats were subjected to
ischemic stroke while they were conscious by infusing
endothelin-1 (Et-1) through a guide
cannula that was implemented in the vicinity of the middle cerebral artery (MCA). Rats were given
subcutaneous injections of
IGF-1 (1 mg/kg) at 30 min and 120 min after the insult. Post-
stroke IGF-1 treatment reduced the
infarct size by 34% and 38% in aged and adult rats, respectively. The
IGF-1 treated adult rats also showed significant improvement in sensorimotor function following
stroke, while this function was not significantly affected in aged rats. Furthermore, aged rats displayed exaggerated activation of microglia in the ischemic hemisphere. Significant reduction of microglial activation by
IGF-1 was only detected at specific regions in the ipsilateral hemisphere of adult rats. We show that
IGF-1 reduced
infarct size in aged rats with an
ischemic stroke. It remains to be established, however, whether the age-related changes in microglial function affect the improvement in behavioral outcomes.