| Objectives : The present study was to examine the effects of post-extinction rapid eye movement sleep deprivation(RSD) on recall of fear extinction。Methods: Experiment 1:On Day 1,rats were transported to context A to habituate them to the context;On Day 2(fear conditioning phase), Rats received five pairings of tone and footshock in context A ; The next day(extinction training phase),rats received ten tone-alone extinction trials in context A,immediately,0-6 h RSD rats were placed in the RSD apparatus and 6-12 h RSD rats and control rats were placed in their homecages,six hours later,6-12 h RSD rats were placed in the RSD apparatus;On Day 4(recall test phase),rats received ten additional extinction trials in context A。Experiment 2:On Day 1,rats were transported to context A and context B to habituate them to the context; On Day 2(fear conditioning phase),rats received five pairings of tone and footshock in context A;The next day(extinction training phase),rats received ten tone-alone extinction trials in context B,immediately,0-6 h RSD rats were placed in the RSD apparatus and 6-12 h RSD rats and control rats were transported to their homecages,six hours later,6-12 h RSD rats were placed in the RSD apparatus;On Day 4(recall test phase),rats received ten additional extinction trials in context B。Experiment 3:On Day 1,rats were transported to context A and context B to habituate them to the context;On Day 2(fear conditioning phase),rats received five pairings of tone and footshock in context A;On Day 3 (extinction training phase),rats received ten tone-alone extinction trials in context B,immediately, 0-6 h RSD rats were placed in the RSD apparatus and 6-12 h RSD rats and control rats were transported to their homecages,six hours later,6-12 h RSD rats were placed in the RSD apparatus;The next day(recall test phase),rats received ten additional extinction trials in context A。Experiment 4:On Day 1,rats were transported to context A and to habituate them to the context;On Day 2(fear conditioning phase),rats received five footshocks without tone presentation in context A;On Day 3 (extinction training phase),rats received a 20 min extinction session in same context and were immediately deprived of REM sleep for six hours(0-6 h RSD) or placed in their home cages(6-12 h RSD and control groups),six hours later,6-12 h RSD rats were placed in the RSD apparatus; The next day(recall test phase),rats received an additional 20 min extinction session。Previous stuies showed that recall of extinction is hippocampus-independent in experiment 1 and experiment 2,whereas they are hippocampus-dependent tasks in experiment 3 and experiment 4。Percent of time spent freezing was scored and analysed during fear condioning phase,extinction training phase and recall test phase。Results:Experiment 1:We found no significant group effect among 0-6 h RSD,6-12 h RSD and control groups on fear conditioning phase and extinction training phase;RSD from 0-6 h significantly increased freezing whereas there is no significant group effect between 6-12 h RSD and control groups on recall test phase。Experiment 2:We found no significant effect among 0-6 h RSD,6-12 h RSD and control groups on fear conditioning phase and extinction training phase;RSD from 0-6 h significantly increased freezing whereas there is no significant group effect between 6-12 h RSD and control groups on recall test phase。There is no significant effect among 0-6 h RSD,6-12 h RSD and control groups on fear conditioning phase,extinction training phase and recall test phase in experiment 3 and experiment 4。 Conclusion:These results suggest that the effects of post-extinction RSD on memory for fear extinction are complex。RSD impairs recall of fear extinction in hippocampus-independent tasks,but does not affect recall of fear extinction in hippocampus-dependent tasks,and this effect is dependent on the time during which RSD is applied after extinction training。Our findings further support the notion that REM sleep is involved in memory process of certain tasks。...
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