Department of Neurology and Division of Sleep Medicine, Beth Israel Deaconess Medical Center & Harvard Medical School, Boston, MA 02215, USA.
Neuroscience. 2012 Sep 27;221:125-39. doi: 10.1016/j.neuroscience.2012.06.069. Epub 2012 Jul 13.
Forty-five years ago Shik and colleagues were the first to demonstrate that electrical stimulation of the dorsal pontine reticular formation induced fictive locomotion in decerebrate cats. This supraspinal motor site was subsequently termed the "mesencephalic locomotor region (MLR)". Cholinergic neurons of the pedunculopontine tegmental nucleus (PPT) have been suggested to form, or at least comprise in part, the neuroanatomical basis for the MLR, but direct evidence is lacking. In an effort to clarify the location and activity profiles of pontine reticulospinal neurons supporting locomotor behaviors, we employed in the present study a retrograde tracing method in combination with single-unit recordings and antidromic spinal cord stimulation as well as characterized the locomotor- and behavioral state-dependent activities of both reticulospinal and non-reticulospinal neurons. The retrograde labeling and antidromic stimulation responses suggested a candidate group of reticulospinal neurons that were non-cholinergic and located just medial to the PPT cholinergic neurons and ventral to the cuneiform nucleus (CnF). Unit recordings from these reticulospinal neurons in freely behaving animals revealed that the preponderance of neurons fired in relation to motor behaviors and that some of these neurons were also active during rapid eye movement sleep. By contrast, non-reticulospinal neurons, which likely included cholinergic neurons, did not exhibit firing activity in relation to motor behaviors. In summary, the present study provides neuroanatomical and electrophysiological evidence that non-cholinergic, pontine reticulospinal neurons may constitute the major component of the long-sought neuroanatomic MLR in mammals.
45 年前，Shik 及其同事首次证明，电刺激脑桥背侧网状结构可在去大脑猫中诱发虚拟运动。这个脊髓上运动部位随后被称为“中脑运动区（MLR）”。被盖腹侧脑桥核（PPT）中的胆碱能神经元被认为形成了 MLR 的神经解剖基础，或者至少部分构成了 MLR 的神经解剖基础，但缺乏直接证据。为了阐明支持运动行为的桥脑网状脊髓神经元的位置和活动特征，我们在本研究中采用逆行示踪法结合单个神经元记录和逆行脊髓刺激，并对网状脊髓和非网状脊髓神经元的运动和行为状态相关活动进行了特征描述。逆行标记和逆行刺激反应提示了一组候选的网状脊髓神经元，它们是非胆碱能的，位于 PPT 胆碱能神经元的内侧，楔状核（CnF）的腹侧。在自由活动动物中记录这些网状脊髓神经元的活动发现，大多数神经元的活动与运动行为有关，其中一些神经元在快速眼动睡眠期间也很活跃。相比之下，非网状脊髓神经元，可能包括胆碱能神经元，其活动与运动行为无关。总之，本研究提供了神经解剖学和电生理学证据，表明非胆碱能的桥脑网状脊髓神经元可能构成哺乳动物中苦苦寻找的长程 MLR 的主要组成部分。
