Changes of hippocampal gray matter volume and immune related genes in dizocilpine-induced schizophrenia model rats / 中华行为医学与脑科学杂志

ABSTRACT

Objective:To investigate the changes of hippocampal gray matter volume and expression of candidate immune related genes in a rat model of schizophrenia established by repeated administration of dizocilpine(MK-801).Methods:Thirty SPF grade Sprague-Dawley male rats at postnatal day 28 were randomly divided into MK-801 medium-dose (0.25 mg/kg) group, MK-801 high-dose(0.50 mg/kg) group and normal saline (5 mL/kg) group according to random number table method, with 10 in each group.Rats were given continuous intraperitoneal administration according to grouping once a day for 14 days.Open field test, novel object recognition test and Y-maze test were used at postnatal day 60 to detect spontaneous activity, exploration ability, anxiety level, object recognition memory ability and spatial working memory of rats, respectively.At postnatal day 67, structural magnetic resonance imaging was used to detect the changes of hippocampal gray matter volume in rat.And at postnatal day 70, qRT-PCR was used to detect the expression of candidate immune-related genes in rat hippocampus.SPSS 25.0 was used for statistical analysis, one-way ANOVA was used for comparison among multiple groups, and Tukey test was used for further pairwise comparisons.Results:(1)The behavioral results showed that there were significant differences in the total movement distance, central area activity time, novel object recognition index, and spontaneous correct alternation rate among the three groups ( F=11.15, 10.11, 13.62, 11.99, all P<0.05). The total movement distances in MK-801 medium-dose group and MK-801 high-dose group ((21.44±2.17) m, (22.87±1.96)m) were higher than that in the normal saline group ((18.70±1.88) m) (both P<0.05). The activity time of the central area in the MK-801 medium-dose group and MK-801 high-dose group((3.24±1.58) s, (2.50±1.32) s) were lower than that of the normal saline group ((6.05±2.48)s) (both P<0.01). Novel object recognition indexes in the MK-801 medium-dose group and MK-801 high-dose group((56.10±3.99)%, (54.00±6.41)%) were both lower than that in the normal saline group ((65.90±5.65)%)(both P<0.01), and the rates of spontaneous correct alternation ((54.60±7.03)%, (51.60±8.84)%) in the two groups were lower than that of the normal saline group ((68.40±8.57)%) (both P<0.01). (2) The results of structural magnetic resonance imaging showed that there were significant differences in the volume of hippocampal gray matter among the three groups ( F=9.24, P<0.001). The volumes of hippocampal gray matter in MK-801 medium-dose group and MK-801 high-dose group were lower than that in normal saline group(both P<0.001). (3)By constructing protein-protein interaction network, four candidate immune related genes were screened out: neuropeptide Y (NPY), somatostatin (SST), cholecystokinin (CCK) and tachykinin 1 (TAC1). The results showed that the mRNA expression levels of NPY, SST and CCK in the hippocampus of the three groups were significantly different ( F=11.41, 10.43, 5.85, all P<0.05), but there was no statistical difference in the TAC1 mRNA expression level ( F=0.08, P>0.05). The mRNA levels of NPY, SST and CCK in the hippocampus of rats in the MK-801 high-dose group were lower than those in the normal saline group (all P<0.05). Conclusion:Both medium dose and high dose MK-801 administration can reduce the volume of hippocampal gray matter in schizophrenia model rats, but they have different effects on the expression of hippocampal immune related genes, of which high dose administration has a greater effect.