Neurokinin receptors modulate the impact of uncontrollable stimulation on adaptive spinal plasticity.

Previous research has demonstrated that spinally transected rats can acquire a prolonged flexion response to prevent the delivery of shock. However, rats that receive shock irrespective of leg position cannot learn to maintain the same response. The present experiments examined the role of neurokinin receptors in this learning deficit. Results demonstrated that neurokinin (NK1 and NK2) antagonists blocked the induction of the learning deficit, whereas NK agonists induced a learning deficit. The study found that NK agonist administration did not substitute for uncontrollable shock exposure. Finally, administration of an NK1 agonist prior to uncontrollable shock prevented the induction of the deficit. These results provide additional evidence that engaging nociceptive plasticity undermines the capability of spinal neurons to support adaptive changes.