Data from: Substance P signalling in primary motor cortex facilitates motor learning in rats

Among the genes that are up-regulated in response to a reaching training in rats, Tachykinin 1 (Tac1) - a gene that encodes the neuropeptide Substance P (Sub P) - shows an especially strong expression. Using Real-Time RT-PCR, a detailed time-course of Tac1 expression could be defined: a significant peak occurs 7 hours after training ended at the first and second training session, whereas no up-regulation could be detected at a later time-point (sixth training session). To assess the physiological role of Sub P during movement acquisition, microinjections into the primary motor cortex (M1) contralateral to the trained paw were performed. When Sub P was injected before the first three sessions of a reaching training, effectiveness of motor learning became significantly increased. Injections at a time-point when rats already knew the task (i.e. training session ten and eleven) had no effect on reaching performance. Sub P injections did not influence the improvement of performance within a single training session, but retention of performance between sessions became strengthened at a very early stage (i.e. between baseline-training and first training session). Thus, Sub P facilitates motor learning in the very early phase of skill acquisition by supporting memory consolidation. In line with these findings, learning related expression of the precursor Tac1 occurs at early but not at later time-points during reaching training.

在大鼠抓握训练诱导的上调基因中，速激肽1（Tachykinin 1, Tac1）——一种编码神经肽P物质（Substance P, Sub P）的基因——表现出尤为显著的表达水平。借助实时定量逆转录聚合酶链反应（Real-Time RT-PCR），研究人员明确了Tac1基因表达的精细时间进程：在首次与第二次训练回合结束后的7小时，其表达量达到显著峰值；而在较晚的时间节点（第六次训练回合）则未检测到表达上调。为探究P物质在运动技能习得过程中的生理功能，研究团队对与训练侧爪对侧的初级运动皮层（primary motor cortex, M1）开展了显微注射实验。若在首次三轮抓握训练前注射P物质，运动学习的效果会显著提升；而当大鼠已熟练掌握该任务时（即第十、十一次训练回合）进行注射，则对抓握表现无显著影响。P物质注射不会改变单次训练回合内的表现提升幅度，但可在极早期阶段强化训练回合间的表现留存（即基线训练与首次训练回合之间）。综上，P物质可通过支持记忆巩固，在技能习得的极早期阶段促进运动学习。这一结论与“Tac1基因的学习相关表达仅出现在抓握训练早期，而非后期”的实验结果相一致。