| Objective: To investigate the effects of lactation repeated intermittent inhalation ofsevoflurane clinical anesthetic concentration and subanesthetic concentrations on thelearning and memory ability in juvenile and adult rats.Methods: twenty-four healthy Sprague-dawley rats, aged7days, were randomly dividedinto3groups (n=8each): control group(group C),1.5%sevoflurane(group S1), and2.6%sevoflurane(group S2). At7,14and21days after birth,1.5%and2.6%sevoflurane andcarrier gas were inhaled for1h in group S1, S2and C, respectively. Record the onsetand recovery time of anesthesia during each inhalation and respiratory rate before inhalationanesthesia, at the onset moment, in the30th minute of the onset and anesthesia recovery. Allof the rats were experimented Morris water maze test in the28th day after birth. Morriswater maze test in the juvenile stage consists of3parts, including the cued platformtrial, place navigation test and spatial probe test, lasted9days. Cued platform trial wascarried out on28and29days after birth(P28, P29), and the swimming speed and distanceof the rats was recorded.2days of rest after the cued platform trial. Place navigation testwas performed on P32～P36, and the escape latency, swimming distance and searchstrategy was recorded. Spatial probe test was carried out on P36, the percentage of originalplatform quadrant retention time, movement distance, entering frequency and the time spentin the platform quadrant, swimming distance, the number of times crossing the platformfrom quadrant was recorded.All of rats were fed to adult, Morris water maze test in the adult stage consists of3parts,including the positioning navigation test, spatial probe test and the learning to reachcriterion test, started from the91th day, lasted for14days. Positioning navigation test, carried out on P91～P95, while the spatial probe test start at P95. Theexperimental method and recording index were similar with juvenile stage. The learning toreach criterion test was carried out on P96～P104, lasted for9days, record the number oflearned platforms and the number of trials used to reach the criteria.Results:⑴The onset and recovery time of anesthesia: In group S1, the3onset time (min)of anesthesia were6,7,9, respectively, recovery time (min) were12,7,6; While in groupS2, the3onset time (min) were4,6,8and recovery time (min) were31,15,12.⑵Respiratory rate during inhalation: In group S1and S2,the respiratory rate at the onset timeof anesthesia and the30th minute of the onset decreased significantly compared withpre-anesthesia(P<0.01); There was no statistical significance in the respiratory rate betweenpre-anesthesia and anesthesia convalescence(P>0.05).⑶In the cued platform trial, theswimming distance was significantly longer at P29than P28(P<0.01). There were nosignificantly differences in the three groups in swimming speed (P>0.05).⑷In the placenavigation test, there were significant statistical differences in the constituent ratio of searchstrategy among rats of different test day(P<0.01), With the increasing of the number of daysto test, random and marginal strategy gradually reduced; While straight and tendencystrategy increased.⑸In the juvenile stage of place navigation test, the escape latency ofgroup S2were longer than group C at1,2,4,5d(P<0.05),while the escape latency of groupS1were longer than group C at1,4,5d(P<0.05), and the escape latency of group S2werelonger than group S1at2d(P<0.05). The escape latency of group S1, S2were shorter thanbefore from3d of place trials (P<0.05), while the escape latency of group C were shorterthan before from4d of place trials (P<0.05). In the adult stage of place navigation test, theescape latency of group S1were longer than group C at4d (P<0.05). The escape latency ofgroup S2, C were shorter than before at5d of place trials (P<0.05), while the escape latencyof group S1were no significantly differences in the5th days (P>0.05).⑹In the juvenilestage of place navigation test, the swimming distance of group S2were longer than group Cat2,4,5d(P<0.05), while the swimming distance of group S2were longer than group S1at2d(P<0.05). The swimming distance of group S2were shorter than before from3d of placetrials (P<0.05), while the swimming distance of group S1, C were shorter than before from 2d of place trials(P<0.05). In the adult stage of place navigation test, there were nosignificantly differences in all groups of rats either between groups or within group(P>0.05).⑺In the juvenile stage of spatial probe test, no significant differences among allgroups of rats in percentage of original platform quadrant retention time,movement distance and entering frequency(P>0.05). In adult stage, the percentage oforiginal platform quadrant retention time in group S122.07±6.93(%) was decreased thanthat in group C31.52±4.53(%)(P<0.05). Percentage of original platform quadrantmovement distance in group S120.20±4.95(%) was decreased than that in group C28.96±6.57(%)(P<0.05).⑻In the spatial probe test, the time spent in the platform quadrant,swimming distance and the number of times crossing the platform from quadrant in juvenileperiod were no significant differences in the three groups(P>0.05). In the adult probe trials,the number of times crossing the platform from quadrant in group S11.86±0.90(times)shorter than group C28.96±6.57(times)(P<0.05).⑼In the learning to reach criterion test,the number of learned platforms and the number of trials used to reach the criteria were nosignificant differences in the three groups (P>0.05).Conclusion:⑴Repeated inhalation of sevoflurane during lactation can impair the declarative memory,which is concentration-related, while it has no effects on the space association ability andrecall inquisition ability in juvenile rats.⑵Repeated inhalation clinical concentration of sevoflurane during lactation may have noeffects on the associative learning and working memory in adulthood.⑶Repeated inhalation subanesthetic concentration of sevoflurane during lactation canimpair the associative learning, while it has no effects on the working memory in adulthood. |
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