Tag Archives: Learned Helplessness

The effect of neonatal Handling on the learned helplessness model of depression.

Researchers examined the effects of neonatal handling on learned helplessness (LH) in rats.  They discuss prior research that showed a variety of benefits associated with neonatal handling such as improved escape latency and lower emotional reactivity.  They express that rats who have been handled have a permanent augmentation of the glucocorticoid receptors in their hippocampi.

In this study researchers used Wistar Rats and sorted them into two groups.  One group received daily 15 minute handling and the other received no handling.  After 21 days mice were tested for emotional reactivity in an open field test. LH was induced 72 hours after the completion of the open field test using an automated shuttle box shock chamber.

Results showed that on the first day escape failures for both the handled group and the non-handled group were similar.  On the second and third day escape failures dramatically reduced for the handled group. However the non-handled group did not see a similar reduction in escape failures and only saw a slight reduction.

They then went on to examine escape latency times and avoidance behavior.  Like the escape failures, both handled groups and non-handle groups had similar times on the first day for both measurements.  On the second and third day the handled group showed increasingly better escape times and increasingly more avoidance behavior.  The non-handled group did better on each subsequent day but the improvement was modest.

Researchers observed that handled rats showed more avoidance escape behavior when they were subjected to uncontrollable shocks.  They speculate that the changes are the result of locomotor activity changes induced by the neonatal handling.

Costela, C., Tejedor-real, P., Mico, J.A., & Gibert-Rahola, J. (1995) Effect of neonatal Handling on learned helplessness model of depression.  Physiology And Behavior.  57(2), 407-410.  

Impairment of spatial learning and memory induced by learned helplessness and chronic mild stress.

This study examined the influence of learned helplessness (LH) and chronic mild stress (CMS) on spatial learning and memory in mice.  Researchers indicate that the hippocampal complex plays an important role in many common psychiatric disorders, spatial awareness, and is also involved in LH which is similar to depression in humans.  

There were 6 groups of mice with 12 mice in each group.  One control group for each independent (LH, CMS, or no stressor) variable and then each group has a similar a group that would receive an anti-depressant, “Imi” or “Flu”, to evaluate its effect.  Researchers induced LH using traditional shuttle box electric shock method. To induce CMS they used a variety of stressors that were presented at unpredictable times. Mice were also evaluated for plasma corticosterone levels and BDNF and CREB levels in the hippocampus were evaluated to asses stress and LH effects.

The research indicated that both Imi and Flu significantly reduced the number of escape failures in LH mice over the course of 18 days.  It also indicates that Imi and Flu reduced corticosterone in CMS mice over the course of 18 days. Additionally, both BDNF and CREB were improved with Imi and Flu.  Its notable that even though the drugs improved these measures, the levels never reached the same as the non-conditioned non-stressed mice.  

Lastly researchers evaluated mice in a Morris water maze.  Stressed mice performed significantly worse on escape times.  However, both Imi and Flu improved escape times. Interestingly mice who were not stressed but received Flu anyways did even better regarding escape times than mice who did not receive Flu.  

Song, L., Che, W., Min-wei, W., Murakami, Y., & Matsumoto, K.  (2006) Impairment of the spatial learning and memory induced by learning helplessness and chronic mild stress.  Pharmacology Biochemestry And Behavior.  83, 186-193.