OBJECTIVETo observe the changes in anxiety-like behavior among rats in the recovery stage after hypoxic-ischemic brain damage (HIBD) during the perinatal period and to investigate the effect of insulin-like growth factor 1 (IGF-1) on the long-term anxiety-like behavior and its action mechanism among rats with HIBD.

METHODSNinety neonatal rats (7 days old) were randomly and equally divided into normal control, HIBD, and HIBD+IGF-1 groups. A neonatal rat model of HIBD was established by Rice method in the HIBD and HIBD+IGF-1 groups. The rats in the HIBD+IGF-1 group were intraperitoneally injected with IGF-1 (0.2 mg/kg) immediately after HIBD, and the other two groups were intraperitoneally injected with an equal volume of normal saline. The anxiety-like behavior was evaluated by elevated plus-maze test on postnatal days 21 and 28. The expression of tyrosine hydroxylase (TH) in the substantia nigra was measured by immunohistochemistry on postnatal days 14, 21, and 28.

RESULTSOn postnatal days 21 and 28, the open-arm time (OAT) and percentage of OAT for the HIBD and HIBD+IGF-1 groups were significantly lower than those for the normal control group (P<0.05), but there were no significant differences between the HIBD and HIBD+IGF-1 groups (P>0.05); the percentage of open arm entry showed no significant difference between the three groups (P>0.05). On postnatal day 14, there were no significant differences in percentage of TH immunostaining-positive area between the three groups (P>0.05). On postnatal days 21 and 28, the HIBD and HIBD+IGF-1 groups had significantly lower percentages of TH immunostaining-positive area than the normal control group (P<0.05), but there was no significant difference between the HIBD and HIBD+IGF-1 groups (P>0.05).

CONCLUSIONSHIBD in the perinatal period may cause the changes in anxiety-like behavior in adolescent rats, which may be related to decreased expression of TH in the substantia nigra. Neonatally given IGF-1 cannot improve the long-term anxiety-like behavior in rats after HIBD, and it does not affect TH expression in the substantia nigra. IGF-1 may not regulate the changes in long-term anxiety-like behavior in adolescent rats.