Summary
Responses of motoneurons supplying muscles of the forelimbs, hindlimbs, back, and neck to stimulation of the medial pontomedullary reticular formation were studied with intracellular recording in cere-bellectomized cats under chloralose anesthesia.
Stimulation of the midline or of a reticular region consisting of nucleus reticularis (n.r.) pontis caudalis and the dorsorostral part of n.r. gigantocellularis produced monosynaptic excitation of ipsilateral motoneurons supplying axial muscles and flexor and extensor muscles in both proximal and distal parts of the limbs. This widespread excitation appears to have been produced by rapidly conducting medial reticulospinal fibers.
Stimulation of a second region consisting of n.r. ventralis and the ventrocaudal part of n. r. gigantocellularis produced monosynaptic excitation of ipsilateral neck and back motoneurons but only longer latency, apparently multisynaptic excitation of limb motoneurons. Collision tests indicated that this monosynaptic excitation did not involve fibers descending along the midline. It therefore appears to have been produced by lateral reticulospinal fibers.
Reticular stimulation also produced short latency, monosynaptic inhibition of neck motoneurons, long latency, apparently polysynaptic inhibition of limb motoneurons and intermediate latency inhibition of back motoneurons. The latencies and properties of inhibitory responses of back motoneurons indicated that they were produced either disynaptically by fast fibers or monosynaptically by slower fibers.
The data indicate that the medial pontomedullary reticular formation can be divided into a number of different zones each with a distinct pattern of connections with somatic motoneurons. These include the dorsorostrally located medial reticulospinal projection area, from which direct excitation of a wide variety of motoneurons can be evoked, the ventrocaudally located lateral reticulospinal projection area from which direct excitation of neck and back and direct inhibition of neck motoneurons can be evoked and the dorsal strip of n.r. gigantocellularis which has direct excitatory and inhibitory actions only on neck motoneurons.
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Akaike, T., Fanardjian, V.V., Ito, M., Ohno, T.: Electrophysiological analysis of the vestibulospinal reflex pathway of rabbit. II. Synaptic actions upon spinal neurones. Exp. Brain Res. 17, 497–515 (1973)
Brodal, A.: The reticular formation of the brain stem. pp. 8–12. Edinburgh: Oliver and Boy 1957
Eccles, J.C., Nicoll, R.A., Rantucci, T. Táboříková, H., Willey, T.J.: Topographic studies on medial reticular nucleus. J. Neurophysiol. 39, 109–118 (1976)
Grillner, S., Lund, S.: The origin of a descending pathway with monosynaptic action on flexor motoneurones. Acta Physiol. Scand. 74, 274–284 (1968)
Grillner, S., Hongo, T., Lund, S.: Convergent effects on alpha motoneurones from the vestibulospinal tract and a pathway descending in the medial longitudinal fasciculus. Exp. Brain Res. 12, 457–479 (1971)
Ito, M., Udo, M., Mano, N.: Long inhibitory and excitatory pathways converging onto cat's reticular and Deiters' neurons, and their relevance to the reticulofugal axons. J. Neurophysiol. 33, 210–226 (1970)
Jankowska, E., Lund, S., Lundberg, A., Pompeiano, O.: Inhibitory effects evoked through ventral reticulospinal pathways. Arch. Ital. Biol. 106, 124–140 (1968)
Jankowska, E., Lundberg, A., Roberts, W.J., Stuart, D.: A long propriospinal system with direct effect on motoneurones and interneurones in the cat lumbosacral cord. Exp. Brain Res. 21, 169–194 (1974)
Kawamura, K., Brodal, A., Höddevik, G.: The projection of the superior colliculus onto the reticular formation of the brain stem. An experimental anatomical study in the cat. Exp. Brain Res. 19, 1–19 (1974)
Klüver, H., Barrera, E.: A method for the combined staining of cells and fibers in the nervous system. J. Neuropathol. Exp. Neurol. 12, 400–403 (1953)
Kuypers, H.G.J.M.: The descending pathways to the spinal cord, their anatomy and function. In: Organization of the spinal cord. Eccles, J.C., Schadé, J. (eds.), pp. 178–200. New York: Elsevier 1964
Kuypers, H.G.J.M., Maisky, V.A.: Retrograde axonal transport of horseradish peroxidase from spinal cord to brain stem cell groups in the cat. Neurosci. Lett. 1, 9–14 (1975)
Ladpli, R., Brodal, A.: Experimental studies of commissural and reticular formation projections from the vestibular nuclei in the cat. Brain Res. 8, 65–96 (1968)
Llinás, R., Terzuolo, C.A.: Mechanisms of supraspinal actions upon spinal cord activities. Reticular inhibitory mechanisms on alpha-extensor motoneurons. J. Neurophysiol. 27, 579–591 (1964)
Lloyd, D.P.C.: Activity in neurons of the bulbospinal correlation system. J. Neurophysiol. 4, 115–134 (1941)
Magoun, H.W., Rhines, R.: An inhibitory mechanism in the bulbar reticular formation. J. Neurophysiol. 9, 165–171 (1946)
Nyberg-Hansen, R.: Functional organization of descending supraspinal fibre systems to the spinal cord. Anatomical observations and physiological correlations. Ergebn. Anat. Entwickl.-Gesch. 39, 1–48 (1966)
Peterson, B.W.: Identification of reticulospinal projections that may participate in gaze control. In: Control of gaze by brain stem neurons, developments in neuroscience, Vol. 1. Baker, R., Berthoz, A. (eds.). Amsterdam: Elsevier/North-Holland Biomedical Press 1977
Peterson, B.W., Abzug, C.: Properties of projections from vestibular nuclei to medial reticular formation in the cat. J. Neurophysiol. 38, 1421–1435 (1975)
Peterson, B.W., Anderson, M.E., Filion, M.: Responses of ponto-medullary reticular neurons to cortical, tectal and cutaneous stimuli. Exp. Brain Res. 21, 19–44 (1974)
Peterson, B.W., Coulter, J.D.: A new long spinal projection from the vestibular nuclei in the cat. Brain Res. 122, 351–356 (1977)
Peterson, B.W., Maunz, R.A., Pitts, N.G., Mackel, R.G.: Patterns of projection and branching of reticulospinal neurons. Exp. Brain Res. 23, 333–351 (1975)
Peterson, B.W., Pitts, N.G., Fukushima, K., Mackel, R.: Reticulospinal excitation and inhibition of neck motoneurons. Exp. Brain Res. 32, 471–489 (1978)
Petras, J.M.: Cortical, tectal and tegmental fiber connections in the spinal cord of the cat. Brain Res. 6, 275–324 (1967)
Rhines, R., Magoun, H.W.: Brain stem facilitation of cortical motor response. J. Neurophysiol. 9, 219–229 (1946)
Rossi, G.F., Brodal, A.: Terminal distribution of spinoreticular fibers in the cat. Arch. Neurol. Psychiat. (Chic.) 78, 439–453 (1957)
Walberg, F., Pompeiano, O., Westrum, L.E., Haughlie-Hanssen, E.: Fastigioreticular fibers in the cat. An experimental study with silver method. J. Comp. Neurol. 119, 187–199 (1962)
Wilson, V.J., Maeda, M.: Connections between semicircular canals and neck motoneurons in the cat. J. Neurophysiol. 37, 346–357 (1974)
Wilson, V.J., Yoshida, M.: Comparison of effects of stimulation of Deiters' nucleus and medial longitudinal fasciculus on neck, forelimb and hindlimb motoneurons. J. Neurophysiol. 32, 743–758 (1969)
Wilson, V.J., Yoshida, M., Schor, R.H.: Supraspinal monosynaptic excitation and inhibition of thoracic back motoneurons. Exp. Brain Res. 11, 282–295 (1970)
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Supported in part by NSF Grant BMS 7500487 and N. I. H. Grants EY 02249, EY 00100 and NS 02619
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Peterson, B.W., Pitts, N.G. & Fukushima, K. Reticulospinal connections with limb and axial motoneurons. Exp Brain Res 36, 1–20 (1979). https://doi.org/10.1007/BF00238464
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DOI: https://doi.org/10.1007/BF00238464