title: Organization of pontine reticulospinal inputs to motoneurons controlling axial and limb muscles in the neonatal mouse.
abstract: Using optical recording of synaptically mediated calcium transients and selective spinal lesions, we investigated the pattern of activation of spinal motoneurons (MNs) by the pontine reticulospinal projection in isolated brain stem-spinal cord preparations from the neonatal mouse. Stimulation sites throughout the region where the pontine reticulospinal neurons reside reliably activated MNs at cervical, thoracic, and lumbar levels. Activation was similar in MNs ipsi- and contralateral to the stimulation site, similar in medial and lateral motor columns that contain trunk and limb MNs, respectively, and similar in the L2 and L5 segments that predominantly contain flexor and extensor MNs, respectively. In nonlesioned preparations, responses in both ipsi- and contralateral MNs followed individual stimuli in stimulus trains nearly one-to-one (with few failures). After unilateral hemisection at C1 on the same side as the stimulation, responses had substantially smaller magnitudes and longer latencies and no longer followed individual stimuli. After unilateral hemisection at C1 on the side opposite to the stimulation, the responses were also smaller, but their latencies were not affected. Thus we distinguish two pontine reticulospinal pathways to spinal MNs, one uncrossed and the other crossed, of which the uncrossed pathway transmits more faithfully and appears to be more direct.
authors.affiliation: Laboratory of Neural Development and Optical Recording (NDEVOR), Department of Physiology, Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, Oslo, Norway; and.
authors.forename: Magne S
authors.initials: MS
authors.lastname: Sivertsen
authors.affiliation: Laboratory of Neural Development and Optical Recording (NDEVOR), Department of Physiology, Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, Oslo, Norway; and.
authors.forename: Joel C
authors.initials: JC
authors.lastname: Glover
authors.affiliation: Department of Physiology, Emory University School of Medicine, Atlanta, Georgia m-c.perreault@emory.edu.
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Perreault
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D020013:Calcium Signaling; D005121:Extremities / Q000502:physiology; D051379:Mice; D008813:Mice, Inbred ICR; D009046:Motor Neurons / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D065821:Pontine Tegmentum / Q000502:physiology*; D013116:Spinal Cord / Q000502:physiology*
keywords: brain stem; descending pathways; limb; motor control; spinal cord; trunk