Martin-Cortecero Jesus, Nuñez Angel
Departamento de Anatomía, Histología y Neurociencia, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain.
Departamento de Anatomía, Histología y Neurociencia, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain.
Brain Res. 2014 Dec 3;1591:27-37. doi: 10.1016/j.brainres.2014.10.002. Epub 2014 Oct 13.
Response adaptation is associated with attenuation of neural responses as the result of different mechanisms. However, the main function of adaptation may be to enhance the flow of relevant information transmission in sensory pathways. To study tactile response adaptation in the somatosensory pathway, unit recordings were performed in the principal trigeminal nucleus, ventro postero-medial thalamic nucleus and barrel cortex by means of tungsten microelectrodes in urethane anesthetized rats. Tactile stimuli consisted in 20 ms duration whisker deflections at different frequencies (0.5-10 Hz). Presumably pyramidal cortical neurons showed response adaptation at frequencies >2 Hz while putative inhibitory cortical neurons did not show response adaptation at 0.5, 5 or 10 Hz. Inhibitory activity was increased by muscimol application into the cortex (8mM, 0.1 µl); in this condition cortical adaptation was not affected, suggesting that adaptation was not due to an increase of inhibitory mechanisms. Adaptation was also observed in subcortical structures although the response attenuation was lesser than in the barrel cortex. Adaptation remained in subcortical structures after reversible cortical inactivation by cooling the barrel cortex. Acetylcholine application (10 μM; 0.1 μl) into the barrel cortex reduced response adaptation through the activation of muscarinic receptors because the effect was blocked by intraperitoneal injection of atropine (1mg/kg), suggesting that adaptation may change according to the cortical Ach level. Results indicate that response adaptation increases along the somatosensory pathway probably to alter the sensitivity of neurons in order to encode sensory stimuli more efficiently and to enhance the detectability of rare stimuli.
响应适应与由于不同机制导致的神经反应衰减相关。然而，适应的主要功能可能是增强感觉通路中相关信息传递的流量。为了研究体感通路中的触觉响应适应，在乌拉坦麻醉的大鼠中，通过钨微电极在三叉神经主核、丘脑腹后内侧核和桶状皮层进行单位记录。触觉刺激包括不同频率（0.5 - 10Hz）下持续20毫秒的触须偏转。推测锥体细胞在频率>2Hz时表现出响应适应，而假定的抑制性皮层神经元在0.5、5或10Hz时未表现出响应适应。通过向皮层注射蝇蕈醇（8mM，0.1μl）可增加抑制性活动；在这种情况下，皮层适应不受影响，这表明适应并非由于抑制机制的增加。在皮层下结构中也观察到了适应，尽管响应衰减程度小于桶状皮层。通过冷却桶状皮层使皮层可逆失活后，皮层下结构中的适应仍然存在。向桶状皮层注射乙酰胆碱（10μM；0.1μl）通过激活毒蕈碱受体降低了响应适应，因为该效应被腹腔注射阿托品（1mg/kg）阻断，这表明适应可能会根据皮层乙酰胆碱水平而改变。结果表明，响应适应沿体感通路增加，可能是为了改变神经元的敏感性，以便更有效地编码感觉刺激并提高对罕见刺激的可检测性。
