The Effects Of 5-HT_2C Receptor On LTP In The Primary Visual Cortex Of Adult Rats With Form Deprivation In Vitro

BackgroundThe visual impairment caused by abnormal visual perception during the visual developmental sensitivity is called amblyopia,the treatment of adult amblyopia is disputed and its therapeutic effect is not ideal.It has been proved that the long-term use of fluoxetine in adult amblyopia can obviously reverse the metastasis of ocular dominant column and promote the recovery of visual function,but the mechanism is not clear.However,5-hydroxytryptamine?5-HT?as an important amine neurotransmitter,is widely distributed in the retina and visual cortex of mammals,which can induce long-term synaptic plasticity and ocular dominance plasticity.In addition,it has been proved that the expression of5-hydroxytryptamine-2C subunit receptor(5-HT_2CR)in the visual cortex of strabismus amblyopia cats is significantly lower than that of normal cats from morphology,so there are less reports on the visual cortex in the adult amblyopia rats with monocular form deprivation.ObjectivesIn this study,the effects of 5-hydroxytryptamine hydrochloride and 5-HT_2CR blocker SB 242084 on the long-term potentiation?LTP?in the V1M area of the visual cortex of the adult amblyopia rats were investigated by establishing the adult amblyopia rat model of monocular form deprivation.Reactivation of synaptic plasticity in the visual cortex of adult amblyopia will provide a new theoretical basis for the treatment of adult amblyopia.Methods1.Groups:16 unopened SD?Spargue-Dawley?rats were randomly divided into normal control group?NC group?and monocular deprivation group?MD group?,8 rats/group.The rats in NC group did not do any treatment,MD group were treated with right eyelid suture.After successful modeling,the rats were reared for 6 weeks??8 weeks old?.2 groups of rats were sacrificed and coronary cut into 400?m thick visual cortical brain slices and incubated in artificial cerebrospinal fluid?ACSF?.According the addition of different drugs in ACSF,2 groups of visual cortex slices were divided into 9 groups:normal control visual cortex group?NC group??deprived eye contralateral visual cortex group?CC group??deprived eye ipsilateral visual cortex group?IC group??deprived eye contralateral visual cortex normal saline group?CCI group??deprived eye ipsilateral visual cortex normal saline group?ICI group??deprived eye contralateral visual cortex 5-hydroxytryptamine hydrochloride group?CCII group??deprived eye ipsilateral visual cortex5-hydroxytryptamine hydrochloride group?ICII group??deprived eye contralateral visual cortex SB 242084 combined with 5-hydroxytryptamine hydrochloride group?CCIII group?,deprived eye ipsilateral visual cortex SB 242084 combined with5-hydroxytryptamine hydrochloride group?ICIII group?.NC?CC?IC groups without any drugs,CCI?ICI groups added normal saline,CCII?ICII groups added 5-hydroxytryptamine hydrochloride?10?mol/L?,CCIII?ICIII groups added SB 242084?10?mol/L?and5-hydroxytryptamine hydrochloride?10?mol/L?.2.Electrophysiological experiments:Electrophysiological experiments were performed on the above visual cortex slices by extracellular field potential recording,and the LTP was recorded in the visual cortex V1M.3.Data analysis:The fPSP slope?fPSP slope?was calculated by 10%and 50%of the amplitude of PSP descending wave,and the fPSP slope of basic stimulus?10 min?was100%,the fPSP slope after HFS?51⁶0 min?was analyzed by SPSS21.0 software,and the statistical results were expressed as mean±standard error of mean.NC?CC?IC groups were analyzed by one-way ANOVA with multiple comparisons among the sample numbers.The independent sample t test were used in CCI and CCII groups?ICI and ICII groups?CCII and CCIII groups?ICII and ICIII groups.The differences were statistically significant if P<0.05.Results1.Comparison of the fPSP slope?%?between HFS induced normal visual cortex group and monocular form deprivation bilateral visual cortex groups:NC group was?198.1±13.5?%,IC group was?144.5±2.9?%,CC group was?106.3±8.3?%,the differences between the 3 groups were statistically significant?F=197.594,P<0.001?,and NC group was the highest,CC group was the lowest,the differences were statistically significant?P<0.001?.2.Effects of 5-hydroxytryptamine hydrochloride on fPSP slope?%?in bilateral visual cortex of monocular form deprivation groups:CCI group was?106.3±8.3?%,CCII group was?157.1±9.7?%,CCII group was higher than CCI group,the differences were statistically significant?t=-10.833,P<0.001?;ICI group was?144.5±2.9?%,ICII group was?192.2±8.6?%,ICII group was higher than ICI group,the differences were statistically significant?t=-10.616,P<0.001?,and ICII group was higher than CCII group,the differences were statistically significant?t=-6.841,P<0.001?.3.Effects of SB 242084 combined with 5-hydroxytryptamine hydrochloride on fPSP slope?%?in bilateral visual cortex of monocular form deprivation groups:CCIII group was?102.6±4.7?%,CCII group was?157.1±9.7?%,CCIII group was lower than CCII group,the differences were statistically significant?t=11.872,P<0.001?;ICIII group was?129.7±13.5?%,ICII group was?192.2±8.6?%,ICIII group was lower than ICII group,the differences were statistically significant?t=9.911,P<0.001?,and ICIII group was higher than CCIII group,the differences were statistically significant?t=-3.910,P<0.05?.Conclusion1.The fPSP slope of bilateral visual cortex in adult rats with monocular form deprivation was significantly lower than that of normal rats.It was suggested that monocular deprivation in the critical period could inhibit the neurotransmission of bilateral visual cortex in adult rats,and the fPSP slope of contralateral visual cortex was smaller than that of ipsilateral visual cortex.2.5-hydroxytryptamine hydrochloride can improve the fPSP slope of bilateral visual cortex in adult rats with monocular deprivation.It suggests that 5-hydroxytryptamine hydrochloride can restore the neurotransmitters in the visual cortex of adult amblyopia rats in a certain extent and reactivate the synaptic plasticity in the visual cortex of adult amblyopia rats,which mainly through 5-HT_2CR function.