To investigate the protective effect of L-theanine on nerve function in rats with focal cerebral ischemia.

One hundred male SPF-grade SD rats were randomly divided into a sham-operated group and a model group. Focal cerebral ischemia was induced in the model group using the thread embolism method. The surviving rats were randomly assigned model control group, Edaravone injection group (0.9 mg/kg), low, medium and high doses of L-theanine (50, 100, 200 mg/kg) according to neural function scores. The sham-operated group and the model control group received an equal volume of pure water via intragastric administration, while the other groups received their respective treatments once a day for 14 consecutive days. Neurological function score, grip strength, and bipedal balance were tested at 7 and 14 days after administration, respectively. Gait analysis and cerebral blood flow measurements were performed after the final administration, followed by histopathological examination of brain tissue. One-way ANOVA was used for comparison between multiple groups, and LSD-t test was used for intergroup comparisons.

In the focal cerebral ischemia rat model, significant motor dysfunction was observed. On days 7 and 14, the model group showed significantly higher neurological function scores (3.0±0.0 vs 0.0±0.0 in sham-operated group; t=0.679, 2.208, all P=0.001), increased hindlimb pressure difference [D7: (62.0±40.8) g; D14: (80.3±32.2) g vs sham-operated group: (3.7±2.7) g and (5.0±2.1) g; t=2.707, 2.608, P=0.032, 0.002], and reduced grip strength [D7: (321.9±28.5) g; D14: (424.1±62.6) g vs sham-operated group: (811.6±60.8) g and (988.5±54.9) g; t=20.632, 19.166, all P=0.001]. After 14 days, the model group also exhibited a greater average body rotation angle [(119.2±28.8)° vs (15.5±9.0)°; t=9.127, P=0.005], and reduced left step width (3.0±2.3 vs 336.0±32.5; t=26.580, P=0.001), speed [(234.9±62.0) mm/s vs (986.5±292.6) mm/s; t=2.531, P=0.001], right forelimb swing duration [(0.04±0.02) s vs (0.13±0.02) s; t=6.742, P=0.001], and right hindfoot pressure [(28.6±2.1) g vs (51.2±7.5) g; t=4.031, P=0.001]. Compared to the model control group, all doses of L-theanine significantly reduced neurological scores and hindlimb pressure differences from day 7 to 14 (all P<0.05). The medium and high doses significantly increased grip strength on D14 (all P<0.05). All L-theanine doses improved gait parameters, including increased left step width, speed, right forelimb swing duration, and right hindfoot pressure (all P<0.05). Medium and high doses of L-theanine also enhanced cerebral blood flow and alleviated pathological changes such as mild neural fiber swelling (all P<0.05), interstitial edema, and cellular infiltration.

L-theanine can significantly improve the motor dysfunction after cerebral ischemia, increases cerebral blood flow, reduces brain tissue pathology, and exerts a notable protective effect on neurological function following cerebral ischemia.