Effect of ganglioside on spatial learning and memory of rats following radiative encephalopathy

Yamei TANG; Yinyin ZHANG; Limei WANG; Songhua XIAO; Jun SHEN; Yigang XING

ABSTRACT

BACKGROUND:

Memory loss is the main presentation during the earlier stage of radiative eneephalopathy, and it was reported that ganglioside (GM1) played important role in neural rehabilitation, particular in the improvement of memory.

OBJECTIVE:

To study the improving effect of GM1 on spatial learning and memory retardation in rats following radiative encepholopathy.

DESIGN:

Randomized control and comparative observing study based on the experimental animals.

SETTING:

Department of Neurology and Department of Radiation of Second Affiliated Hospital of Sun Yat-sen University.MATERIALS This study was carried out at the Laboratory of the Second Hospital Affiliated to Sun Yat-sen University between March 2001 and May 2002. Tctally 80 SD rats were randomly selected and divided into control group, GM1 treatment group, physiological saline group and non-intervention group with 20 rats in each group.

INTERVENTIONS:

Rats in GM1 group, physiological saline group and non-intervention group subjected to head 60Coγ irradiation of 7Gy each time after anesthesia, once a day for consecutive 6 days, and the total dosage was 42Gy while rats in control group did not receive irradiation after anesthesia. Rats in GM1 and physiological saline(PS) group were given intraperitoneal injection of GM1 and physiological saline of 30 mg/kg respectively at 1 hour after each time of radiation, once a day for consecutive 6 days but not in control group and non-intervention group. Evaluation ①After irradiation, morris water labyrinth navigation test was used to assess the capability of learning and memory of rats by the time for reaching platform (latency); ② Spatial searching test was used to detect their spatial memory after learning how to reach the platform by recording the way of rats searching the platform in 120 s and calculating the percentage of swimming distance in platform quadrant in the total distance; ③ After labyrinth test, brains were taken out of the rats in GM1 group, PS group and non-intervention group for observing the histological and pathological changes in rat brains.

RESULTS:

① The latency become stable form onset of the 4th day in each group. On the 5th day, the searching platform latency in GM1 group was(13.6±1.4) s, shorter than(17.1±2.9) s of PS group and [(15.8±2.2) s, (P＜0.05)] of non-intervention group; ② Rats in GM 1 and control group were found capable of searching platform according to their spatial memory, presented by swimming trail most located in platform quadrant while rats in PS and non-intervention groups were found mostly swimming around the pool with moving trails distributed randomly. The percentage of swimming distance in platform quadrant was found higher in GM 1 treatment group than in the PS group and non-intervention group, but lower than that in the control group; ③ Histological examination revealed slight neuronal degeneration in PS group, part of which was changes of vacuolar degeneration with cell shrank, chromosome concentrated and nuclei gathered aside, and the number of astrocytes also decreased; the pathological changes in non-intervention group and PS group were similar; in GM1 group, part neurons became smaller with peripalsm turning red but the pathological changes, such as the number of cells,neuclei shrank and gathered aside, and vacuolar changes were less than those of the former two groups.ONCLUSION Radiative encephalopathy would result in obvious learning nd memory impairments in rats but histological and pathological changes due o brain radiation injury can be attenuated with the treatment of GM1, implying that GM1 may play important role in the improvement of radiation-induced spatial learning and memory loss.