Changes of auditory evoked potential P50 of sensory gating in model rats with Alzheimer disease

Yuhong ZHU; Tinghua WANG; Bing SUN; Zhuo ZHANG; Yan YAN; Zhitong HAN; Zhongtang FENG

ABSTRACT

BACKGROUND:

Auditory evoked potential P50 (AEP-P50) is a cerebroeilectrophysiological index to directly reflect normal inhibitory function of brain.

OBJECTIVE:

To observe the changes of AEP-P50 of sensory gating (SG)in model rats with Alzheimer disease (AD).

DESIGN:

Randomized controlled animal study.

SETTING:

Neuroscience Institute of Kunming Medical College.MATERIALS A total of 24 healthy female SD rats, aged 4-6 months,weighing 200-300 g, were randomly divided into experimental group, control group and normal group with 8 in each group. Morris water maze was consisted of round pool and lucite plant. Pool was divided into platform,left, right and bilateral quadrants.

METHODS:

The experiment was carried out in the Neuroscience Institute of Kunming Medical College from September 2003 to March 2005. ① Experimental group Bilateral fimbria-fornix was transected to induce AD models; control group Except fimbria-fornix, cortex and callus were transected; normal group Rats were not treated with any operation. ② One week after modeling, all rats were tested with Morris water maze which contained localizing navigational ability and spatial seeking ability in order to determine successful models. Each rat was trained 4 times a day for successive 5 days. The duration from putting in pool to finding out platform was regarded as the escape latency (EL) which could reflect localizing navigational ability. Swimming trace of rats which searched platform within 1 minute could reflect spatial seeking ability. ③ AEP-P50 was recorded with "condition (C)-test (T)" auditory double clicks stimuli, additionally,differences of AEP-P50 among the three groups were compared at the same time. C-P50 amplitude, T-P50 amplitude, T/C and absolute value of difference of S2-S1 amplitude were calculated. Measurement data were compared with one-way analysis of variance among groups and with t test intergroup.MAIN OUTCOME

MEASURES:

① Morris water maze, I.e., comparison between localizing navigational ability a nd spatial seeking ability; ② comparison of AEP-P50 of rats among three groups.

RESULTS:

All 24 rats were involved in the fin al analysis. ① results of Morris water maze With increase of training time, mean latency was shortened. The latency was decreased in the first 3 days and then stabilized gradually. Latency in experimental group was longer than that in normal group and control group (P ＜ 0.05). Swimming traces in normal group and control group were located at platform quadrant, and they were accounted for 45.23% and 39.7% of total quadrant, respectively. There was significant difference as compared with other quadrants (P ＜ 0.01). Swimming traces of rats in experimental group were accounted for 28.31%, 29.84%,20.47% and 21.38% in platform, right, bilateral and left quadrants, respectively; however, there was not significant difference (P ＞ 0.05). Swimming trace was randomly located in four quadrants. ② Results of AEP-P50 of SG C-P50 amplitude and absolute value of difference of S2-S1 amplitude were (21.00±2.85), (15.26±4.07) μV in control group and (17.04±5.32), (10.85 ±4.24) μV in normal group, which were obviously higher than those in experimental group [(9.67±3.77), (2.89±2.61) μV, P ＜ 0.01].T-P50 amplitude and C-P50 amplitude were 0.25±0.18 in control group and 0.39±0.16 in normal group, which were lower than those in experimental group (0.92±0.41, P ＜ 0.01).

CONCLUSION:

① Transection of bilateral fimbria-fornix can be used to establish AD animal models successfully. ② AD model rats whose bilateral fimbria-fornix is transected have deficiency of SG.