ERK2 and CREB activation in the amygdala when an event is remembered as “Fearful” and not when it is remembered as “Instructive”

Abstract

A training protocol was developed based on durable exposure to the two-way shuttle avoidance task, in which the conditioned stimulus (CS), which was fear evoking for both training conditions on the first day of training, becomes instructive at the end of training under controllable conditions but remains fear evoking under the uncontrollable conditions. The protocol was utilized to examine whether, depending on the training regime, the memory formed will result in a different level of involvement of the amygdala. Three groups of rats were tested: controllable, subjected to durable avoidance learning; uncontrollable, subjected to the same training schedule but with no control over the stressor; and naive. Two weeks later, after the introduction of a reminder cue, freezing response, defecation, and blood corticosterone (CORT) of the uncontrollable group were higher than in the controllable and naive groups, indicating that indeed, for this group, the CS remained fear evoking. Significantly higher than chance shuttling responses of the controllable group indicated that, for them, the CS became "instructive." Activation of ERK2 and CREB in the basolateral amygdala (BLA) was highest in the uncontrollable group compared with the controllable and naive groups. Overall, the results indicate that the training procedure succeeded in dissociating between the physical (electric shock) and the psychological (control) attributes of the experience. Also, our findings support the view that an emotionally charged reminder cue activates the amygdala but that, as a previously fear-evoking memory cue becomes instructive, the involvement of the amygdale lessens.

Periaqueductal Grey differential modulation of Nucleus Accumbens and Basolateral Amygdala plasticity under controllable and uncontrollable stress

“…Beginning from the 2 nd day of training, animals increasingly performed more avoidance responses compared to escape responses and escape-failures. These results are in line with previous studies regarding gaining controllability over the course of prolonged exposure to the TWSA task 12, 14, 20 . Prolonged TWSA exposure induced different behavioural states as was evident in the test performed two weeks following the initial exposure phase.…”

“…These differences were evident in each stage within the test. The current results along with previous studies 12, 20 indicate that even after the cessation of exposure to the CS-reminder during the test (i.e., the 2 nd and last 3 min free exploration), uncontrollable animals continued to exhibit higher levels of immobility, indicating that uncontrollable rats did not show extinction of fear.…”

Periaqueductal Grey differential modulation of Nucleus Accumbens and Basolateral Amygdala plasticity under controllable and uncontrollable stress

“…Beginning from the 2 nd day of training, animals increasingly performed more avoidance responses compared to escape responses and escape-failures. These results are in line with previous studies regarding gaining controllability over the course of prolonged exposure to the TWSA task 12, 14, 20 . Prolonged TWSA exposure induced different behavioural states as was evident in the test performed two weeks following the initial exposure phase.…”

“…These differences were evident in each stage within the test. The current results along with previous studies 12, 20 indicate that even after the cessation of exposure to the CS-reminder during the test (i.e., the 2 nd and last 3 min free exploration), uncontrollable animals continued to exhibit higher levels of immobility, indicating that uncontrollable rats did not show extinction of fear.…”

Age-related impairments in memory and in CREB and pCREB expression in hippocampus and amygdala following inhibitory avoidance training

“…The results obtained in hippocampal regions agree with a number of other studies showing increased hippocampal CREB phosphorylation following inhibitory avoidance training in young adult rats, which can be abolished by treatments that interfere with memory processes (Cammarota et al, 2000; Taubenfeld et al, 2001, 1999; Viola et al, 2000). The amygdala results also agree with several studies demonstrating enhanced CREB phosphorylation in the basolateral and/or lateral amygdala following fearful or stressful stimuli (Bilang-Bleuel et al, 2002; Hubbard et al, 2007; Ilin and Richter-Levin, 2009; Kogan and Richter-Levin, 2008; Lin et al, 2003; Saha and Datta, 2005; Shen et al, 2004; Stanciu et al, 2001). …”

Controllability affects endocrine response of adolescent male rats to stress as well as impulsivity and behavioral flexibility during adulthood

“…Whether this reflects lower levels of fear to the context in CST rats (this parameter being more sensitive to minor differences in fear than freezing) or a reinforced response to move to the other compartment even in the absence of signals announcing shocks is unclear. The finding that intercrossings during the habituation was essentially similar between sessions 2 and 8 whereas intercrossings during the ITIs progressively increased favors the hypothesis of lower levels of fear in CST rats, in accordance with prior reports in adult rats using a CST-UST design also involving a TWAA task in which fear conditioning to the context was evaluated several days after the procedure 52,56 . The development of fear conditioning after CST/UST has also been evaluated by Liu et al .…”

“…Therefore, the influence of control was not evident during the first session but appeared when animals had repeated experience with the procedure. The existence of HPA differences in the present study between CST and UST rats with several days of experience with the task and not in the first session gives support to the proposal that the “experience of controllability” develops across time 52 . Interestingly, the correlation between ACTH and total time of shock during session 8 was significant in UST but not in CST rats.…”

Periaqueductal Grey differential modulation of Nucleus Accumbens and Basolateral Amygdala plasticity under controllable and uncontrollable stress

“…Beginning from the 2 nd day of training, animals increasingly performed more avoidance responses compared to escape responses and escape-failures. These results are in line with previous studies regarding gaining controllability over the course of prolonged exposure to the TWSA task 12, 14, 20 . Prolonged TWSA exposure induced different behavioural states as was evident in the test performed two weeks following the initial exposure phase.…”

“…These differences were evident in each stage within the test. The current results along with previous studies 12, 20 indicate that even after the cessation of exposure to the CS-reminder during the test (i.e., the 2 nd and last 3 min free exploration), uncontrollable animals continued to exhibit higher levels of immobility, indicating that uncontrollable rats did not show extinction of fear.…”

Age-related impairments in memory and in CREB and pCREB expression in hippocampus and amygdala following inhibitory avoidance training

“…The results obtained in hippocampal regions agree with a number of other studies showing increased hippocampal CREB phosphorylation following inhibitory avoidance training in young adult rats, which can be abolished by treatments that interfere with memory processes (Cammarota et al, 2000; Taubenfeld et al, 2001, 1999; Viola et al, 2000). The amygdala results also agree with several studies demonstrating enhanced CREB phosphorylation in the basolateral and/or lateral amygdala following fearful or stressful stimuli (Bilang-Bleuel et al, 2002; Hubbard et al, 2007; Ilin and Richter-Levin, 2009; Kogan and Richter-Levin, 2008; Lin et al, 2003; Saha and Datta, 2005; Shen et al, 2004; Stanciu et al, 2001). …”

Controllability affects endocrine response of adolescent male rats to stress as well as impulsivity and behavioral flexibility during adulthood

“…Whether this reflects lower levels of fear to the context in CST rats (this parameter being more sensitive to minor differences in fear than freezing) or a reinforced response to move to the other compartment even in the absence of signals announcing shocks is unclear. The finding that intercrossings during the habituation was essentially similar between sessions 2 and 8 whereas intercrossings during the ITIs progressively increased favors the hypothesis of lower levels of fear in CST rats, in accordance with prior reports in adult rats using a CST-UST design also involving a TWAA task in which fear conditioning to the context was evaluated several days after the procedure 52,56 . The development of fear conditioning after CST/UST has also been evaluated by Liu et al .…”

“…Therefore, the influence of control was not evident during the first session but appeared when animals had repeated experience with the procedure. The existence of HPA differences in the present study between CST and UST rats with several days of experience with the task and not in the first session gives support to the proposal that the “experience of controllability” develops across time 52 . Interestingly, the correlation between ACTH and total time of shock during session 8 was significant in UST but not in CST rats.…”

Periaqueductal Grey differential modulation of Nucleus Accumbens and Basolateral Amygdala plasticity under controllable and uncontrollable stress

“…Beginning from the 2 nd day of training, animals increasingly performed more avoidance responses compared to escape responses and escape-failures. These results are in line with previous studies regarding gaining controllability over the course of prolonged exposure to the TWSA task 12, 14, 20 . Prolonged TWSA exposure induced different behavioural states as was evident in the test performed two weeks following the initial exposure phase.…”

“…These differences were evident in each stage within the test. The current results along with previous studies 12, 20 indicate that even after the cessation of exposure to the CS-reminder during the test (i.e., the 2 nd and last 3 min free exploration), uncontrollable animals continued to exhibit higher levels of immobility, indicating that uncontrollable rats did not show extinction of fear.…”

Age-related impairments in memory and in CREB and pCREB expression in hippocampus and amygdala following inhibitory avoidance training

“…The results obtained in hippocampal regions agree with a number of other studies showing increased hippocampal CREB phosphorylation following inhibitory avoidance training in young adult rats, which can be abolished by treatments that interfere with memory processes (Cammarota et al, 2000; Taubenfeld et al, 2001, 1999; Viola et al, 2000). The amygdala results also agree with several studies demonstrating enhanced CREB phosphorylation in the basolateral and/or lateral amygdala following fearful or stressful stimuli (Bilang-Bleuel et al, 2002; Hubbard et al, 2007; Ilin and Richter-Levin, 2009; Kogan and Richter-Levin, 2008; Lin et al, 2003; Saha and Datta, 2005; Shen et al, 2004; Stanciu et al, 2001). …”

Controllability affects endocrine response of adolescent male rats to stress as well as impulsivity and behavioral flexibility during adulthood

“…Whether this reflects lower levels of fear to the context in CST rats (this parameter being more sensitive to minor differences in fear than freezing) or a reinforced response to move to the other compartment even in the absence of signals announcing shocks is unclear. The finding that intercrossings during the habituation was essentially similar between sessions 2 and 8 whereas intercrossings during the ITIs progressively increased favors the hypothesis of lower levels of fear in CST rats, in accordance with prior reports in adult rats using a CST-UST design also involving a TWAA task in which fear conditioning to the context was evaluated several days after the procedure 52,56 . The development of fear conditioning after CST/UST has also been evaluated by Liu et al .…”

“…Therefore, the influence of control was not evident during the first session but appeared when animals had repeated experience with the procedure. The existence of HPA differences in the present study between CST and UST rats with several days of experience with the task and not in the first session gives support to the proposal that the “experience of controllability” develops across time 52 . Interestingly, the correlation between ACTH and total time of shock during session 8 was significant in UST but not in CST rats.…”