Szokol Karolina, Glover Joel C, Perreault Marie-Claude
University of Oslo, Institute of Basic Medical Sciences (Domus Medica), Department of Physiology, N-0317, Oslo, Norway.
J Physiol. 2008 Nov 1;586(21):5259-76. doi: 10.1113/jphysiol.2008.158105. Epub 2008 Sep 4.
To better understand how the brainstem reticular formation controls and coordinates trunk and hindlimb muscle activity, we used optical recording to characterize the functional connections between medullary reticulospinal neurons and lumbar motoneurons of the L2 segment in the neonatal mouse. In an isolated brainstem-spinal cord preparation, synaptically induced calcium transients were visualized in individual MNs of the ipsilateral and contralateral medial and lateral motor columns (MMC, LMC) following focal electrical stimulation of the medullary reticular formation (MRF). Stimulation of the MRF elicited differential responses in MMC and LMC, according to a specific spatial organization. Stimulation of the medial MRF elicited responses predominantly in the LMC whereas stimulation of the lateral MRF elicited responses predominantly in the MMC. This reciprocal response pattern was observed on both the ipsilateral and contralateral sides of the spinal cord. To ascertain whether the regions stimulated contained reticulospinal neurons, we retrogradely labelled MRF neurons with axons coursing in different spinal funiculi, and compared the distributions of the labelled neurons to the stimulation sites. We found a large number of retrogradely labelled neurons within regions of the gigantocellularis reticular nucleus (including its pars ventralis and alpha) where most stimulation sites were located. The existence of a mediolateral organization within the MRF, whereby distinct populations of reticulospinal neurons predominantly influence medial or lateral motoneurons, provides an anatomical substrate for the differential control of trunk and hindlimb muscles. Such an organization introduces flexibility in the initiation and coordination of activity in the two sets of muscles that would satisfy many of the functional requirements that arise during postural and non-postural motor control in mammals.
为了更好地理解脑干网状结构如何控制和协调躯干及后肢肌肉活动,我们利用光学记录来表征新生小鼠延髓网状脊髓神经元与L2节段腰段运动神经元之间的功能连接。在一个分离的脑干-脊髓标本中,在对延髓网状结构(MRF)进行局部电刺激后,同侧和对侧内侧及外侧运动柱(MMC、LMC)的单个运动神经元中可观察到突触诱导的钙瞬变。根据特定的空间组织,对MRF的刺激在MMC和LMC中引发了不同的反应。刺激内侧MRF主要在LMC中引发反应,而刺激外侧MRF主要在MMC中引发反应。在脊髓的同侧和对侧均观察到这种相互反应模式。为了确定受刺激区域是否包含网状脊髓神经元,我们用在不同脊髓白质束中走行的轴突逆行标记MRF神经元,并将标记神经元的分布与刺激部位进行比较。我们在巨细胞网状核区域(包括其腹侧部和α部)发现了大量逆行标记的神经元,而大多数刺激部位位于该区域。MRF内存在的内侧-外侧组织,即不同群体的网状脊髓神经元主要影响内侧或外侧运动神经元,为躯干和后肢肌肉的差异控制提供了解剖学基础。这样一种组织在两组肌肉活动的启动和协调中引入了灵活性,这将满足哺乳动物在姿势和非姿势运动控制过程中出现的许多功能需求。