The effect of music exposure in juvenile stage on anxiety-like behavior and fear extinction in adult rat

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Objective To study the effect of music exposure in juvenile stage on anxiety-like behavior and fear extinction in adult rats. Methods 4 broods of two-week-old healthy Sprague-Dawleyda rats were separated into two groups randomly. The music groups were exposed to music from 20∶00 to 22∶00 for 21 consecutive days. When the rats were 5 weeks old, they were caged by sex, with 8 male rats and 6 female rats in each group. When the rats were 8 weeks old, the two groups were assessed in the elevated-plus maze test, the open-field test, trained and assessed by the conditional fear training and fear extinction training. Results In the elevated-plus maze test: Prior to the foot shock, the percent of time spent in the open arms in the music group (female(7.07±1.14)%, male(5.12±1.95)%) exhibited no significant difference (P>0.05) comparing with the rats in the control group (female(4.65±0.86)%, male(4.86±1.95)%). After the foot shock, the percent of time spent in the open arms in the music group (female(8.63±3.35)%, male(7.79±2.49)%) increased comparing to the control group (female(1.48±0.11)%, male(4.29±1.68)%)(P 0.05) comparing with the rats in control group (female(5.27±1.95)%, male(6.22±3.13)%). After the foot shock, the percent of time spent in the center zone in the music group (female(8.52±1.93)%, male(6.95±2.46)%) was larger than the control group (female(3.47±0.93)%, male(4.36±2.22)%)(P<0.05). The fear extinction training showed that the percent of freezing time exhibited no significant difference between the male and female rats of the music group and control group in the first block of the first extinction training day and the percentage of freezing time of female rats in music group was significantly lower than that of female rats in control group on the third extinction training day. The percentage of freezing time of male rats in the music group was significantly lower than that of male rats in control group on the second and third training day. Conclusion Music exposure in juvenile stage decreases the anxiety level after foot shock, and promotes the long-term fear extinction, while has no effect on the level of fear memory. Key words: Music; Anxiety; Rat; Fear extinction