The Effects of Behavioral Training on Spinal Plasticity and ERK1/2 Phosphorylation, Within the Injured Spinal Cord
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Previous research has shown that even when communication between the brain and spinal cord has been eliminated, rats can learn a simple instrumental response. If rats receive shock to one hindlimb when it is extended (controllable shock), subjects will learn to maintain that leg in a flexed position to minimize shock exposure. Conversely, if shock is delivered irrespective of leg position (uncontrollable shock), subjects are unable to maintain the same response and exhibit a learning deficit when later tested with controllable shock. Recent studies have demonstrated that the adaptive modifications accompanying learning and the maladaptive consequences of uncontrollable nociceptive stimulation interact to influence behavioral outcomes. We have shown that the induction of inflammatory processes increases responding to noxious stimuli and undermines the capacity to learn. Behavioral training with controllable shock, on the other hand, protects against these effects, allowing subjects to learn. At the cellular level, the presentation of noxious stimuli increases nuclear iv localization of phosphorylated (activated) extracellular signal-regulated kinases 1 and 2 (ERK1/2). Here, we explore the impact of instrumental training and inflammation on cytosolic ERK1/2 activation. Subjects received 30 min of instrumental training or subcutaneous hindpaw injections of 1% capsaicin (50 μL vol). The lumbar region of the spinal cord (L4-S2) was then collected 0, 3, and 24 hr later, and prepared for western immunoblot analysis. A group of untreated rats were included as controls. We found a time-dependent effect on cytosolic ERK1/2 phosphorylation, with the greatest levels observed 24 hr following treatment. We also found that instrumental training or capsaicin treatment downregulated cytosolic expression of phospho-ERK1 and phospho- ERK2. Taken together, these results suggest that instrumental training and inflammation engage similar signaling pathways. Further work will be integral for determining how the cellular consequences of instrumental training and inflammation interact to produce divergent behavioral outcomes.
Hughes, Abbey (2009). The Effects of Behavioral Training on Spinal Plasticity and ERK1/2 Phosphorylation, Within the Injured Spinal Cord. Available electronically from