| Abstract No.: | A-G1187 |
| Country: | Canada |
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| Title: | NATURAL VARIATIONS IN MATERNAL CARE MODULATE HIPPOCAMPAL LEARNING UNDER STRESS AND SYNAPTIC PLASTICITY IN THE DENTATE GYRUS OF ADULT RATS. |
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| Authors/Affiliations: | 2 Rosemary Bagot*; 3 Felisa van Hasselt; 1 Danielle Champagne; 3 Harm Krugers; 3 Marian Joels; 2 Michael Meaney;
1 Leiden University, Netherlands; 2 McGill University, Montreal, QC, Canada; 3 University of Amsterdam, Netherlands
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| Content: | Objectives: The quality of the postnatal environment has profound effects on development. In rats, the behaviour of the dam is a major determinant of the pup’s early environment. Natural variations in maternal care exert enduring influences on endocrine and behavioural responses to stressors and cognition. As adults, rats that received low levels of maternal licking and grooming (LG) exhibit greater fear responses than rats that received high LG. High LG rats show enhanced spatial learning and object recognition relative to low LG rats. However, it is unclear if high levels of LG produce a universal enhancement of learning and plasticity. Given the greater fearfulness of low LG rats, we hypothesised enhanced learning and plasticity in low LG rats in situations in which aversive stimulation is central.
Materials & Methods: We examined the influence of maternal care on modulation of hippocampal plasticity by stress both in vitro and in vivo. In vitro, we examined the effects of stress hormone activity (corticosterone & isoproterenol, a beta-adrenergic agonist) implicated in the consolidation of learning and memory on long term potentiation (LTP), in the hippocampal dentate gyrus (DG) in adult male offspring of high and low LG. In vivo, we examined the effect of maternal care on contextual fear conditioning, a hippocampal-dependent learning task inherently stressful due to the aversive shock stimulus, and tone-condtioning, a hippocampal-independent task.
Results: Following brief application of corticosterone or isoproterenol, in vitro LTP was significantly increased in the DG of low LG rats but decreased in high LG rats. Consistent with our hypotheses, low LG rats displayed enhanced contextual fear conditioning and did not differ in tone conditioning, a hippocampal-independent task.
Conclusions: The present results suggest that maternal care mediates the influence of stress on hippocampal plasticity, profoundly shaping the animal’s response to stress encountered in its environment throughout life.
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