Limits...
A fear-inducing odor alters PER2 and c-Fos expression in brain regions involved in fear memory.

Pantazopoulos H, Dolatshad H, Davis FC - PLoS ONE (2011)

Bottom Line: These changes were accompanied by increased c-Fos expression at ZT0.In addition, increased c-Fos expression at ZT 12 was only detected in the central nucleus of the amygdala in the TMT12 group.The observed effects on PER2 expression and c-Fos were stronger during the early day than during the early night, possibly to prepare appropriate systems at ZT 0 to respond to a fear-inducing stimulus.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Northeastern University, Boston, Massachusetts, United States of America. hantazo@mclean.harvard.edu

ABSTRACT
Evidence demonstrates that rodents learn to associate a foot shock with time of day, indicating the formation of a fear related time-stamp memory, even in the absence of a functioning SCN. In addition, mice acquire and retain fear memory better during the early day compared to the early night. This type of memory may be regulated by circadian pacemakers outside of the SCN. As a first step in testing the hypothesis that clock genes are involved in the formation of a time-stamp fear memory, we exposed one group of mice to fox feces derived odor (TMT) at ZT 0 and one group at ZT 12 for 4 successive days. A separate group with no exposure to TMT was also included as a control. Animals were sacrificed one day after the last exposure to TMT, and PER2 and c-Fos protein were quantified in the SCN, amygdala, hippocampus, and piriform cortex. Exposure to TMT had a strong effect at ZT 0, decreasing PER2 expression at this time point in most regions except the SCN, and reversing the normal rhythm of PER2 expression in the amygdala and piriform cortex. These changes were accompanied by increased c-Fos expression at ZT0. In contrast, exposure to TMT at ZT 12 abolished the rhythm of PER2 expression in the amygdala. In addition, increased c-Fos expression at ZT 12 was only detected in the central nucleus of the amygdala in the TMT12 group. TMT exposure at either time point did not affect PER2 or c-Fos in the SCN, indicating that under a light-dark cycle, the SCN rhythm is stable in the presence of repeated exposure to a fear-inducing stimulus. Taken together, these results indicate that entrainment to a fear-inducing stimulus leads to changes in PER2 and c-Fos expression that are detected 24 hours following the last exposure to TMT, indicating entrainment of endogenous oscillators in these regions. The observed effects on PER2 expression and c-Fos were stronger during the early day than during the early night, possibly to prepare appropriate systems at ZT 0 to respond to a fear-inducing stimulus.

Show MeSH

Related in: MedlinePlus

TMT exposure does not affect PER2 or c-Fos expression in the SCN.PER2 expression in the SCN was identical for all three groups (A), with expression peaking at ZT 12. (B) c-Fos immunoreactivity was similar to PER2 in the SCN for all three groups. Photomicrographs showing high PER2 expression in the SCN at ZT 12 for the TMT0 group (C) and the TMT12 group (D), and low PER2 expression at ZT 0 for the TMT0 group (E) and the TMT12 group (F). *significantly different from control group at that time point (p<0.05) **significantly different from control and experimental group at that timepoint (p<0.05). The values for ZT 0 are repeated as ZT 24. Error bars represent standard errors.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3105109&req=5

pone-0020658-g002: TMT exposure does not affect PER2 or c-Fos expression in the SCN.PER2 expression in the SCN was identical for all three groups (A), with expression peaking at ZT 12. (B) c-Fos immunoreactivity was similar to PER2 in the SCN for all three groups. Photomicrographs showing high PER2 expression in the SCN at ZT 12 for the TMT0 group (C) and the TMT12 group (D), and low PER2 expression at ZT 0 for the TMT0 group (E) and the TMT12 group (F). *significantly different from control group at that time point (p<0.05) **significantly different from control and experimental group at that timepoint (p<0.05). The values for ZT 0 are repeated as ZT 24. Error bars represent standard errors.

Mentions: Repeated exposure to TMT at either ZT 0 (TMT0) or ZT 12 (TMT12) for four successive days followed by one day without exposure (Figure 1) had no significant effect on the amount PER2 or c-Fos expression when each experimental group was compared to the baseline control group or to each other at each time point (Figure 2). In addition, TMT exposure did not affect the normal rhythm of PER2 or c-Fos expression in the SCN, as a strong effect of ZT was detected in each group (Tables 1 & 2). Identical rhythms in PER2 and c-Fos expression were observed in each group, with a peak of expression for both markers occurring at ZT 12 (Figure 2 A&B).


A fear-inducing odor alters PER2 and c-Fos expression in brain regions involved in fear memory.

Pantazopoulos H, Dolatshad H, Davis FC - PLoS ONE (2011)

TMT exposure does not affect PER2 or c-Fos expression in the SCN.PER2 expression in the SCN was identical for all three groups (A), with expression peaking at ZT 12. (B) c-Fos immunoreactivity was similar to PER2 in the SCN for all three groups. Photomicrographs showing high PER2 expression in the SCN at ZT 12 for the TMT0 group (C) and the TMT12 group (D), and low PER2 expression at ZT 0 for the TMT0 group (E) and the TMT12 group (F). *significantly different from control group at that time point (p<0.05) **significantly different from control and experimental group at that timepoint (p<0.05). The values for ZT 0 are repeated as ZT 24. Error bars represent standard errors.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3105109&req=5

pone-0020658-g002: TMT exposure does not affect PER2 or c-Fos expression in the SCN.PER2 expression in the SCN was identical for all three groups (A), with expression peaking at ZT 12. (B) c-Fos immunoreactivity was similar to PER2 in the SCN for all three groups. Photomicrographs showing high PER2 expression in the SCN at ZT 12 for the TMT0 group (C) and the TMT12 group (D), and low PER2 expression at ZT 0 for the TMT0 group (E) and the TMT12 group (F). *significantly different from control group at that time point (p<0.05) **significantly different from control and experimental group at that timepoint (p<0.05). The values for ZT 0 are repeated as ZT 24. Error bars represent standard errors.
Mentions: Repeated exposure to TMT at either ZT 0 (TMT0) or ZT 12 (TMT12) for four successive days followed by one day without exposure (Figure 1) had no significant effect on the amount PER2 or c-Fos expression when each experimental group was compared to the baseline control group or to each other at each time point (Figure 2). In addition, TMT exposure did not affect the normal rhythm of PER2 or c-Fos expression in the SCN, as a strong effect of ZT was detected in each group (Tables 1 & 2). Identical rhythms in PER2 and c-Fos expression were observed in each group, with a peak of expression for both markers occurring at ZT 12 (Figure 2 A&B).

Bottom Line: These changes were accompanied by increased c-Fos expression at ZT0.In addition, increased c-Fos expression at ZT 12 was only detected in the central nucleus of the amygdala in the TMT12 group.The observed effects on PER2 expression and c-Fos were stronger during the early day than during the early night, possibly to prepare appropriate systems at ZT 0 to respond to a fear-inducing stimulus.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Northeastern University, Boston, Massachusetts, United States of America. hantazo@mclean.harvard.edu

ABSTRACT
Evidence demonstrates that rodents learn to associate a foot shock with time of day, indicating the formation of a fear related time-stamp memory, even in the absence of a functioning SCN. In addition, mice acquire and retain fear memory better during the early day compared to the early night. This type of memory may be regulated by circadian pacemakers outside of the SCN. As a first step in testing the hypothesis that clock genes are involved in the formation of a time-stamp fear memory, we exposed one group of mice to fox feces derived odor (TMT) at ZT 0 and one group at ZT 12 for 4 successive days. A separate group with no exposure to TMT was also included as a control. Animals were sacrificed one day after the last exposure to TMT, and PER2 and c-Fos protein were quantified in the SCN, amygdala, hippocampus, and piriform cortex. Exposure to TMT had a strong effect at ZT 0, decreasing PER2 expression at this time point in most regions except the SCN, and reversing the normal rhythm of PER2 expression in the amygdala and piriform cortex. These changes were accompanied by increased c-Fos expression at ZT0. In contrast, exposure to TMT at ZT 12 abolished the rhythm of PER2 expression in the amygdala. In addition, increased c-Fos expression at ZT 12 was only detected in the central nucleus of the amygdala in the TMT12 group. TMT exposure at either time point did not affect PER2 or c-Fos in the SCN, indicating that under a light-dark cycle, the SCN rhythm is stable in the presence of repeated exposure to a fear-inducing stimulus. Taken together, these results indicate that entrainment to a fear-inducing stimulus leads to changes in PER2 and c-Fos expression that are detected 24 hours following the last exposure to TMT, indicating entrainment of endogenous oscillators in these regions. The observed effects on PER2 expression and c-Fos were stronger during the early day than during the early night, possibly to prepare appropriate systems at ZT 0 to respond to a fear-inducing stimulus.

Show MeSH
Related in: MedlinePlus