The effect of sex differences on the ability of learning and memory and brain tissue damage of newborn rats with hypoxic-ischemic brain damage

Objective To explore the effect of sex difference on learning and memory function and the brain tissue damage of neonatal SD rats with hypoxic-ischemic brain damage. Methods Sixty, 7-day-old neonatal Sprague-Dawley rats, were divided into randomly: male control group (M group, n=15), female control group (F group, n=15), male hypoxic-ischemic brain damage group (MHIBD group, n=15) and female hypoxic-ischemic brain damage group (FHIBD group, n=15). A modified newborn rat model that had a combined hypoxic-ischemic brain damage as described by Rice-Vannucci was used. The Morris water maze was used to evaluate the ability of learning and memory.The brain MRI and transmission electron microscope(TEM) was used to evaluate the scope of brain tissue damage and the change of the synaptic ultrastructure. Results There were no differences in swimming distance, escape latency, synaptic cleft and damage brain volume between M group and F group(P>0.05). Compare with M group and F group, MHIBD group and FHIBD group showed significant brain injury, longer escape latency ((39.38±11.40)s vs (14.86±4.42)s, (30.14±7.18)s vs (18.41±5.03)s), longer swimming distance ((15.31±1.77)cm vs (3.68±1.50)cm, (13.18±1.79)cm vs (4.61±1.61)cm), and TEM showed the synaptic cleft was widened ((23.18±1.36)nm vs (19.24±1.51)nm, (21.40±1.71)nm vs (19.87±0.94)nm), P<0.05). MHIBD group was more seriously compromised than the FHIBD group(P<0.05). The brain MRI showed the damage brain volume of MHIBD group were significantly larger than FHIBD group(P<0.05). Conclusion After hypoxic ischemic brain damage, the tolerance of brain damage and / or post-injury recovery capabilities of female rats are stronger than males. Key words: Sex; Hypoxia-ischemia; Learning and memory; MRI; Ultrastructure