Interaction Between Childbirth Stress And Corticotropin Releasing Factor Receptor 1(CRFR1)on Offspring’s Learning And Memory

Objectives This study aims to examine the effect of CRFR1 signaling in regulating learning and memory function of offspring after experiencing early life stress.Methods1.The C57BL/6N mice model of cesarean delivery(CD)and vaginal delivery(VD)was established.Early life stress paradigm was set up by limiting nesting and bedding material from postnatal day 2(PND2)to PND8.During the stress period,Mice in CD group were divided into CRFR1 antagonist group(CD+ANT)and solvent control group(CD+CON),and mice in VD group were divided into CRFR1 antagonist group(VD+ANT)and control group(VD+CON),respectively.The CRFR1 antagonist group was injected subcutaneously with antalarmin behind the neck every morning,while the solvent control group was injected with solvent.2.The body weight and brain weight of the four groups were recorded at PND0,PND9 and PND42,respectively.3.Open field test was conducted at PND42(equivalent to adolescence)to evaluate offspring’s locomotion ability.The Morris water maze test was performed during PND44-PND49 to evaluate offspring’s learning and memory function.4.Offspring’s peripheral blood was collected at PND0,PND9 and PND50,ELISA was utilized to detect offspring’s serum corticosterone level at different postnatal time points.And the hippocampal tissue was collected at PND9,PND50,synaptic proteins(SYN,PSD-95),cell adhesion molecules(NL1,NL2,NP,nectin-1,and nectin-3),N-methyl-D-aspartcte receptor subunit 1(NR1),2A(NR2A)and 2B(NR2B)protein expression in the hippocampus were detected by Western Blot.Results1.There was no statistical significance in body weight and brain weight among the four groups at PND0,PND9 or PND42.2.At PND0,the serum corticosterone level in CD offspring was significantly lower than that in VD offspring(39.1±2.1 ng/ml vs.46.3±3.5 ng/ml,P=0.045).At PND9 and PND50,there was no significant difference in corticosterone levels between the antagonist injection group and the solvent control group respectively in CD and VD offspring.3.In the open field experiment,there were no significant differences in total distance,average velocity,number of stool particles,number of entries into central quadrant,central quadrant residence time,standing times or grooming times respectively between CD+ANT group and CD+CON group,between VD+ANT group and VD+CON group.4.The five-day water maze navigation exploration test showed that,in CD and VD groups,antalarmin injection did not significantly affect mean total distance,mean speed or mean latency in both CD and VD offspring.The last-day spatial memory experiment indicated that the target quadrant time ratio in CD+ANT group was significantly higher than that in the CD+CON group.There were no significant differences in mean latency,target quadrant crossing times or target quadrant time ratio between VD+ANT and CD+CON groups.5.At PND9,the protein expression level of SYP,NL1,nectin-1,nectin-3,NR2 A and NR2 B protein was significantly higher in CD+ANT group than those in CD+ CON group.The protein expression level of SYP,NL1,NL2,NP,NR1 in the VD+ANT group was significantly higher than those in the VD+CON group.At PND50,the expression level of PSD-95,NL1,NL2,nectin-1,nectin-3,NR2 A and NR2 B protein was significantly higher in CD+ANT group than those in CD+CON group.The NL2,nectin-1 and NR1 protein expression level in the VD+ANT group was significantly higher than those in the VD+ CON group.ConclusionsBlockade of CRFR1 could improve the learning and memory function of caesarean section children(low level birth stress)when they experience chronic stress in early life.This effect was not significant in the offspring of vaginal delivery(normal levels of childbirth stress).