Identification of interneurons with contralateral, caudal axons in the lamprey spinal cord: synaptic interactions and morphology

1982 ◽  
Vol 47 (5) ◽  
pp. 961-975 ◽  
Author(s):  
J. T. Buchanan
Keyword(s):  
Spinal Cord ◽  
Motor Coordination ◽  
Contralateral Side ◽  
Müller Cell ◽  
The Body ◽  
Intracellular Stimulation ◽  
Muller Cell ◽  
Axon Branch ◽  
Dorsal Cells ◽  
Stimulation Of

1. As part of a continuing investigation of the organization of the spinal cord of the lamprey, propriospinal interneurons with axons projecting contralaterally and caudally (CC interneurons) were surveyed with intracellular recordings. 2. CC interneurons were identified by recording their axon spikes extracellularly in the spinal cord during intracellular stimulation of the cell body. The axon projections of Cc interneurons were confirmed after intracellular injection and development of horseradish peroxidase. 3. Intracellular stimulation of CC interneurons produced synaptic potentials in myotomal motoneurons, lateral interneurons and other CC interneurons that lay caudally on the opposite side of the spinal cord. Most CC interneurons were inhibitory, but some were excitatory. 4. CC interneurons were divided into three classes on the basis of reticulospinal Muller cell inputs. CC1 interneurons were excited by the ipsilateral Muller cell B1 and the contralateral Mauthner cell. CC1 interneurons were inhibitory. They were excited polysynaptically by ipsilateral sensory dorsal cells and were inhibited by contralateral dorsal cells. They were distinguished morphologically by having no rostral axon branch and no contralateral dendrites. CC1 interneurons were phasically active during fictive swimming with their peak depolarizations preceding those of myotomal motoneurons by about 0.15 cycle. 5. CC2 interneurons were also inhibitory, but they were distinguished from CC1 interneurons by their excitation from the ipsilateral Muller cells B2-4 nd by their thin rostral and thicker caudal axonal branches on the contralateral side of the spinal cord. 6. CC3 interneurons were excitatory, and they were inhibited by the ipsilateral Muller cell I1. CC3 interneurons could have contralateral dendrites and bifurcating axons, and they had lower average axonal conduction velocities than CC1 and CC2 interneurons. 7. Inhibitory CC interneurons may be important for motor coordination in the lamprey. Movements of the lamprey body during reflexes and swimming consist of contraction and relaxation of myotomal muscles on opposite sides of the body. By being coactive with ipsilateral myotomal motoneurons, inhibitory CC interneurons could contribute to the inhibition of contralateral motoneurons during these movements.

Activities of identified interneurons, motoneurons, and muscle fibers during fictive swimming in the lamprey and effects of reticulospinal and dorsal cell stimulation

1982 ◽  
Vol 47 (5) ◽  
pp. 948-960 ◽  
Author(s):  
J. T. Buchanan ◽  
A. H. Cohen
Keyword(s):  
Spinal Cord ◽  
Muscle Fibers ◽  
Membrane Potentials ◽  
Pattern Generation ◽  
The Body ◽  
Swimming Activity ◽  
Burst Intensity ◽  
Intracellular Stimulation ◽  
Dorsal Cells ◽  
Stimulation Of

1. Application of D-glutamate to the isolated spinal cord of the lamprey produces phasic activity in ventral roots, which is similar to that of the muscles of the intact swimming animal (5,18). Therefore, the isolated spinal cord may be used as a convenient model for the investigation of the generation of locomotor rhythms in a vertebrate. 2. Almost all slow muscle fibers exhibited excitatory junctional potentials (EJPs) during swimming activity. The number of EJPs per cycle increased with the intensity of ventral root (VR) bursting. Few twitch fibers were active, and these fired action potentials only during high intensities of VR bursts. 3. As was found by Russell and Wallen (25), myotomal motoneurons had oscillating membrane potentials during fictive swimming which, on the average, reached a peak depolarization in the middle of the VR burst (phi = 0.21 +/- 0.05; phi = 0 is defined as the onset of the VR burst, and the duration of the cycle is set equal to 1). Membrane potential oscillations in fin motoneurons were antiphasic to those of nearby myotomal motoneurons (peak depolarization phi = 0.68 +/- 0.05). 4. Lateral interneurons had oscillating membrane potentials in synchrony with those of myotomal motoneurons (peak depolarization phi = 0.21 +/- 0.10). Interneurons with axons projecting contralaterally and caudally (CC interneurons) had oscillating membrane potentials that peaked significantly earlier in the cycle (peak depolarization phi = 0.06 +/- 0.12). 5. Edge cells were only weakly modulated during fictive swimming. Their peak depolarizations occurred near the end of the VR burst (phi = 0.33 +/- 0.10). Most giant interneurons were not phasically modulated during fictive swimming. 6. Repetitive intracellular stimulation of Muller cells during fictive swimming generally evoked an increased burst intensity in ipsilateral VRs and a decreased burst intensity in contralateral VRs. The cells M3, B1, and B2 also produced increases or decreases in the frequency of VR bursts. Repetitive intracellular stimulation of sensory dorsal cells could also change the intensities and timing of VR bursts. 7. This study is an initial survey of lamprey spinal interneurons that participate in swimming activity. Lateral interneurons and CC interneurons are active during fictive swimming and probably help coordinate the undulations of the body, but their roles in pattern generation are not known. The central pattern generator is subject to modification by descending and sensory inputs.

Response properties and synaptic connections of mechanoafferent neurons in cerebral ganglion of Aplysia

1979 ◽  
Vol 42 (4) ◽  
pp. 954-974 ◽  
Author(s):  
S. C. Rosen ◽  
K. R. Weiss ◽  
I. Kupfermann
Keyword(s):  
Receptive Field ◽  
Motor Neurons ◽  
Receptive Fields ◽  
Cerebral Ganglion ◽  
The Body ◽  
Sensory Response ◽  
Tactile Stimuli ◽  
Dorsal Portion ◽  
Intracellular Stimulation ◽  
Stimulation Of

1. The cells of two clusters of small neurons on the ventrocaudal surface of each hemicerebral ganglion of Aplysia were found to exhibit action potentials following tactile stimuli applied to the skin of the head. These neurons appear to be mechanosensory afferents since they possess axons in the nerves innervating the skin and tactile stimulation evokes spikes with no prepotentials, even when the cell bodies are sufficiently hyperpolarized to block some spikes. The mechanosensory afferents may be primary afferents since the sensory response persists after chemical synaptic transmission is blocked by bathing the ganglion and peripheral structures in seawater with a high-Mg2+ and low-Ca2+ content. 2. The mechanosensory afferents are normally silent and are insensitive to photic, thermal, and chemical stimuli. A punctate tactile stimulus applied to a circumscribed region of skin can evoke a burst of spikes. If the stimulus is maintained at a constant forces, the mechanosensory response slowly adapts over a period of seconds. Repeated brief stimuli have little or no effect on spike frequency within a burst. 3. Approximately 81% of the mechanoafferent neurons have a single ipsilateral receptive field. The fields are located on the lips, the anterior tentacles, the dorsal portion of the head, the neck, or the perioral zone. Because many cells have collateral axons in the cerebral connectives, receptive fields elsewhere on the body are a possibility. The highest receptive-field density was associated with the lips. Within each area, receptive fields vary in size and shape. Adjacent fields overlap and larger fields frequently encompass several smaller ones. The features of some fields appear invariant from one animal to the next. A loose form of topographic organization of the mechanoafferent cells was observed. For example, cells located in the medial cluster have lip receptive fields, and most cells in the posterolateral portion of the lateral clusters have tentacle receptive fields. 4. Intracellular stimulation of individual mechanoafferents evokes short and constant-latency EPSPs in putative motor neurons comprising the identified B-cell clusters of the cerebral ganglion. On the basis of several criteria, these EPSPs appear to be several criteria, these EPSPs appear to be chemically mediated and are monosynaptic. 5. Repetitive intracellular stimulation of individual mechanoafferent neurons at low rates results in a gradual decrement in the amplitude of the EPSPs evoked in B cluster neurons. EPSP amplitude can be restored following brief periods of rest, but subsequent stimulation leads to further diminution of the response. 6. A decremented response cannot be restored by strong mechanical stimulation outside the receptive field of the mechanoafferent or by electrical stimulation of the cerebral nerves or connectives...

Pattern of Motor Coordination Underlying Backward Swimming in the Lamprey

2006 ◽  
Vol 96 (1) ◽  
pp. 451-460 ◽  
Author(s):  
Salma S. Islam ◽  
Pavel V. Zelenin ◽  
Grigori N. Orlovsky ◽  
Sten Grillner ◽  
Tatiana G. Deliagina
Keyword(s):  
Spinal Cord ◽  
Motor Coordination ◽  
Anterior Part ◽  
Dorsal Side ◽  
The Body ◽  
Large Area ◽  
Lower Vertebrate ◽  
Complete Transection ◽  
Lateral Body ◽  
Propagating Waves

The main form of locomotion in the lamprey (a lower vertebrate, cyclostome) is forward swimming (FS) based on periodical waves of lateral body flexion propagating from head to tail. The lamprey is also capable of backward swimming (BS). Here we describe the kinematical and electromyographic (EMG) pattern of BS, as well as the effects on this pattern exerted by different lesions of the spinal cord. The BS was evoked by tactile stimulation of a large area in the anterior part of the body. Swimming was attributed to the waves of lateral body undulations propagating from tail to head. The EMG bursts on the two sides alternated, and the EMG in more caudal segments led in phase the EMG in more rostral segments. Main kinematical characteristics of BS strongly differed from those of FS: the amplitude of undulations was much larger and their frequency lower. Also, the maintenance of the dorsal-side-up body orientation ascribed to vestibular postural reflexes (typical for FS) was not observed during BS. A complete transection of the spinal cord did not abolish the generation of forward-propagating waves rostral to the lesion. After a lateral hemisection of the spinal cord, the BS pattern persisted on both sides rostral to the lesion; caudal to the lesion, it was present on the intact side and reduced or abolished on the lesioned side. The role of the spinal cord in generation of different forms of undulatory locomotion (FS and BS) is discussed.

Intracellular recording from visually identified motoneurons in rat spinal cord slices

1978 ◽  
Vol 202 (1148) ◽  
pp. 417-421 ◽  
Keyword(s):  
Spinal Cord ◽  
Neuronal Activity ◽  
Intracellular Recording ◽  
Action Potentials ◽  
Intracellular Recordings ◽  
Rat Spinal Cord ◽  
Local Sensitivity ◽  
New Born ◽  
Intracellular Stimulation ◽  
Stimulation Of

Motoneurons were directly visualized with Nomarski optics in slices prepared from new born rat spinal cord. Intracellular recordings from these neurons showed spontaneous potentials, probably triggered by inter-neuronal activity. Action potentials could also be evoked by direct intracellular stimulation of the motoneurons. Iontophoretically applied L-glutamate caused a fast depolarization of the motoneuronal membrane. Considerable differences in local sensitivity to L-glutamate were found on the surface of the motoneuron.

The Origin of the Interoceptive Pathway

2014 ◽  
Author(s):  
A. D. (Bud) Craig
Keyword(s):  
Spinal Cord ◽  
Motor Function ◽  
Contralateral Side ◽  
Dorsal Column ◽  
The Body ◽  
Sensory Loss ◽  
Anatomical Basis ◽  
Touch Sensation ◽  
Temperature Sensations ◽  
The Brain

This chapter describes the functional and anatomical characteristics of interoceptive processing at the levels of the primary sensory fiber and the spinal cord. The association of the spinothalamic pathway with pain and temperature had already been described in textbooks for years. The clinical evidence indicated that a knife cut that severed the spinal cord on one side produced a loss of pain and temperature sensations only on the opposite (contralateral) side of the body, as tested with pinprick and a cold brass rod, combined with the loss of discriminative touch sensation and skeletal motor function on the same (ipsilateral) side as the injury to the spinal cord. The anatomical basis for this dissociated pattern of sensory loss is the distinctness of the two ascending somatosensory pathways to the brain-discriminative touch sensation in the uncrossed (ipsilateral) dorsal column pathway, and pain and temperature sensations in the crossed (contralateral) spinothalamic pathway.

Dopaminergic Modulation of Spinal Neurons and Synaptic Potentials in the Lamprey Spinal Cord

1997 ◽  
Vol 77 (1) ◽  
pp. 289-298 ◽  
Author(s):  
Christopher P. Kemnitz
Keyword(s):  
Spinal Cord ◽  
Membrane Potential ◽  
Cycle Period ◽  
Spinal Neurons ◽  
Postsynaptic Potentials ◽  
Giant Interneurons ◽  
Bath Application ◽  
Dopaminergic Modulation ◽  
Dorsal Cells ◽  
Stimulation Of

Kemnitz, Christopher P. Dopamineric modulation of spinal neurons and synaptic potentials in the lamprey spinal cord. J. Neurophysiol. 77: 289–298, 1997. It has been shown previously that dopamine-immunoreactive cells and processes are present in the lamprey spinal cord and that dopamine modulates the cycle period of fictive swimming. The present study was undertaken to further characterize the effects of dopamine on the cellular properties of lamprey spinal neurons and on inhibitory and excitatory postsynaptic potentials to determine how dopaminergic modulation may affect the central pattern generator for locomotion. Dopamine reduced the late afterhyperpolarization (late AHP) following the action potential of motoneurons, and in three types of sensory neurons: dorsal cells, edge cells, and giant interneurons. The late AHP was not reduced in lateral interneurons or CC interneurons, both of which are part of the central motor pattern generating neural network. The reduction of the late AHP in motoneurons, edge cells, and giant interneurons resulted in an increase in firing frequency in response to depolarizing current injection. In the six cell classes examined, no changes were observed in the resting membrane potential, input resistance, rheobase, spike amplitude, or spike duration after application of dopamine. The durations of action potentials broadened by application of tetraethylammonium in motoneurons and of calcium action potentials in dorsal cells and giant interneurons were decreased after bath application of 10 μM dopamine. The durations of tetrodotoxin-resistant, N-methyl-d-aspartate-induced membrane potential oscillations in lamprey spinal motoneurons were increased after bath application of 1–100 μM dopamine, due perhaps to reduced calcium entry and thus reduced Ca2+-dependent K+ current responsible for the repolarization of the membrane potential during each oscillation. Polysynaptic inhibitory postsynaptic potentials (IPSPs) elicited in lamprey spinal motoneurons by stimulation of the contralateral half of the spinal cord were reduced by bath application of 10 μM dopamine. Polysynaptic excitatory postsynaptic potentials were not reduced by dopamine. Monosynaptic IPSPs in motoneurons elicited by stimulation of single contralateral inhibitory CC interneurons and single ipsilateral axons were reduced by bath application of dopamine (10 μM). Monosynaptic IPSPs in CC interneurons elicited by stimulation of ipsilateral lateral interneurons, however, showed no change after application of dopamine. The lack of dopaminergic effect on the late AHP of the locomotor network neurons, lateral interneurons and CC interneurons, and the selective reduction of IPSPs from CC interneurons suggest that synaptic modulation may play an important role in dopaminergic modulation of cycle period during fictive swimming in the lamprey.

Lateral distribution of hypothalamic signals controlling thermoregulatory vasomotor activity and shivering in rats

1991 ◽  
Vol 260 (3) ◽  
pp. R486-R493 ◽  
Author(s):  
K. Kanosue ◽  
K. Niwa ◽  
P. D. Andrew ◽  
H. Yasuda ◽  
M. Yanase ◽  
...  
Keyword(s):  
Preoptic Area ◽  
Salivary Secretion ◽  
Contralateral Side ◽  
The Body ◽  
Thermal Stimulation ◽  
Hypothalamic Temperature ◽  
Abdominal Skin ◽  
Leg Muscles ◽  
Vasomotor Activity ◽  
Stimulation Of

The present study explored the laterality of central nervous thermoregulatory control in anesthetized rats by measuring paw skin vasomotor activity and cold-induced shivering in hind leg muscles during unilateral preoptic area and anterior hypothalamus (POAH) warming and electrical stimulation or during unilateral thermal stimulation of abdominal skin. Unilateral POAH warming produced vasodilation on both sides of the body, but vasodilation on the ipsilateral side always either occurred at a lower threshold hypothalamic temperature or was stronger than on the contralateral side. In a cold environment (5 degrees C), shivering was suppressed simultaneously in both hind legs when one side of the POAH was warmed, and shivering reappeared simultaneously on both sides when POAH warming stopped. These results suggest that different thermoregulatory effectors are regulated in a different way by each side of the POAH. Unilateral thermal stimulation of the abdominal skin, on the other hand, affected vasomotor activity and shivering equally on both sides of the body, as previously reported for its influence on salivary secretion. Skin thermal signals from both sides of the body therefore seem to converge before they act on different thermoregulatory effector systems.

Visceral and somatic afferent convergence onto neurons near the central canal in the sacral spinal cord of the cat

1985 ◽  
Vol 53 (4) ◽  
pp. 1059-1078 ◽  
Author(s):  
C. N. Honda
Keyword(s):  
Spinal Cord ◽  
Gray Matter ◽  
Receptive Fields ◽  
Central Canal ◽  
The Body ◽  
Wide Range ◽  
Pelvic Viscera ◽  
Somatic Receptive Fields ◽  
Sacral Spinal Cord ◽  
Stimulation Of

One hundred and sixty extracellularly and intracellularly recorded unitary discharges from the sacral or caudal spinal segments of 30 anemically decerebrated cats were studied to examine the effects of somatic and visceral afferent stimulation on neurons near the central canal (CC). The recorded unitary activity was histologically verified (by dye marks or horseradish peroxidase, HRP) as having come from the gray matter surrounding the CC that approximates Rexed's lamina X. In the absence of intentional stimulation or apparent injury by the recording electrode, 62% of the units exhibited ongoing discharges. Each unit was tested for responses to the stimulation of somatic (cutaneous and subcutaneous) and visceral (bladder and colon) structures. Seventy-six (48%) of the units responded exclusively to the stimulation of somatic receptive fields, and 10 (6%) of the units were selectively responsive to stimulation of the pelvic viscera. The activity of the remaining 74 (46%) was influenced by activity in both somatic and visceral afferent fibers. Eighteen of the 160 neurons were intracellularly marked with HRP. Based on perikaryal size and dendritic extent, it was possible to divide these cells into two partially overlapping groups. One group consisted of seven neurons with small to medium-sized perikarya, dendritic arbors largely restricted to the gray matter surrounding the CC, and small, singular somatic receptive fields. The second group comprised 11 cells with medium to large-sized soma and dendrites extending out of lamina X. These larger neurons usually possessed multiple, widely distributed somatic receptive fields. The principal finding of the present study is that in the sacral spinal cord many cells near the CC receive primary afferent inputs converging from a wide range of receptor types in somatic and visceral structures. Such neurons are capable of integrating afferent information from somatic structures on both sides of the body with information originating in pelvic viscera and midline regions such as the genitals.

Reticulospinal neurons controlling forward and backward swimming in the lamprey

2011 ◽  
Vol 105 (3) ◽  
pp. 1361-1371 ◽  
Author(s):  
P. V. Zelenin
Keyword(s):  
Spinal Cord ◽  
Postural Control ◽  
Motor Coordination ◽  
Vestibular Stimulation ◽  
Firing Frequency ◽  
The Body ◽  
Body Orientation ◽  
Locomotor Rhythm ◽  
Reticulospinal Neurons ◽  
Implanted Electrodes

Most vertebrates are capable of two forms of locomotion, forward and backward, strongly differing in the patterns of motor coordination. Basic mechanisms generating these patterns are located in the spinal cord; they are activated and regulated by supraspinal commands. In the lamprey, these commands are transmitted by reticulospinal (RS) neurons. The aim of this study was to reveal groups of RS neurons controlling different aspects of forward (FS) and backward (BS) swimming in the lamprey. Activity of individual larger RS neurons in intact lampreys was recorded during FS and BS by chronically implanted electrodes. It was found that among the neurons activated during locomotion, 27% were active only during FS, 3% only during BS, and 70% during both FS and BS. In a portion of RS neurons, their mean firing frequency was correlated with frequency of body undulations during FS (8%), during BS (34%), or during both FS and BS (22%), suggesting their involvement in control of locomotion intensity. RS activity was phasically modulated by the locomotor rhythm during FS (20% of neurons), during BS (29%), or during both FS and BS (16%). The majority of RS neurons responding to vestibular stimulation (and presumably involved in control of body orientation) were active mainly during FS. This explains the absence of stabilization of the body orientation observed during BS. We discuss possible functions of different groups of RS neurons, i.e., activation of the spinal locomotor CPG, inversion of the direction of propagation of locomotor waves, and postural control.

Coordinated Interlimb Compensatory Responses to Electrical Stimulation of Cutaneous Nerves in the Hand and Foot During Walking

2003 ◽  
Vol 90 (5) ◽  
pp. 2850-2861 ◽  
Author(s):  
Carlos Haridas ◽  
E. Paul Zehr
Keyword(s):  
Electrical Stimulation ◽  
Motor Coordination ◽  
The Body ◽  
Emg Activity ◽  
Motor Tasks ◽  
Step Cycle ◽  
Reflex Responses ◽  
Cutaneous Reflex ◽  
Reflex Pathways ◽  
Stimulation Of

It has been shown that stimulation of cutaneous nerves innervating the hand (superficial radial, SR) and foot (superficial peroneal, SP) elicit widespread reflex responses in many muscles across the body. These interlimb reflex responses were suggested to be functionally relevant to assist in motor coordination between the arms and legs during motor tasks such as walking. The experiments described in this paper were conducted to test the hypothesis that interlimb reflexes were phase-dependently modulated and produced functional kinematic changes during locomotion. Subjects walked on a treadmill while electromyographic (EMG) activity was collected continuously from all four limbs, and kinematic recordings were made of angular changes across the ankle, knee, elbow, and shoulder joints. Cutaneous reflexes were evoked by delivering trains of electrical stimulation pseudorandomly to the SP nerve or SR nerves in separate trials. Reflexes were phase-averaged according to the time of occurrence in the step cycle, and phasic amplitudes and latencies were calculated. For both nerves, significant phase-dependent modulation (including reflex reversals) of interlimb cutaneous reflex responses was seen in most muscles studied. Both SR and SP nerve stimulation resulted in significant alteration in ankle joint kinematics. The results suggest coordinated and functionally relevant reflex pathways from the SP and SR nerves onto motoneurons innervating muscles in nonstimulated limbs during walking, thus extending observations from the cat to that of the bipedal human.

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