==================================BSR36================================== 36. Dendritic potentials in cat spinal cord motor neurons. 1 UI - 87077614 AU - Zhang L ; Krnjevi:c K TI - Effects of 4-aminopyridine on the action potential and the after-hyperpolarization of cat spinal motoneurons. AB - In cats under pentobarbital anaesthesia, intramotoneuronal administrations of 4-aminopyridine significantly prolong the falling phase of the antidromic action potential but have much less effect on the orthodromic action potential. 4-aminopyridine probably blocks the fast K channels involved in the repolarization of the membrane and indirectly activates ionic channels through enhancement of synaptic transmission, also suggested by the potentiation of excitatory postsynaptic potentials. In many cells, 4-aminopyridine depresses the amplitude and prolongs the time course of the after-hyperpolarization; therefore 4-aminopyridine may also partly block Ca2+-activated K+ channels. MH - Action Potentials/DRUG EFFECTS ; Aminopyridines/*PHARMACODYNAMICS ; Animal ; Calcium/PHYSIOLOGY ; Cats ; Ion Channels/*DRUG EFFECTS ; Membrane Potentials ; Motor Neurons/*DRUG EFFECTS ; Potassium/ PHARMACODYNAMICS ; Spinal Cord ; Support, Non-U.S. Gov't SO - Can J Physiol Pharmacol 1986 Nov;64(11):1402-6 2 UI - 87060013 AU - Gustafsson B ; Pinter MJ ; Wigstr:om H TI - The effect of axotomy on posttetanic potentiation of group Ia synapses in the cat. AB - Posttetanic potentiation (PTP) of composite Ia excitatory postsynaptic potentials (EPSPs) has been studied in normal cat alpha-motoneurons and in motoneurons axotomized 2-3 wk earlier by ventral root section. The maximal amount of PTP of EPSP amplitude (expressed relative to unpotentiated amplitude) was considerably less in the axotomized population compared with the normal population. The decrease in PTP provoked by axotomy occurs in association with a postaxotomy increase of input resistance, the net effect being that PTP in axotomized cells was much the same as that observed by others in normal motoneurons possessing similarly high input resistance. In agreement with previous results, EPSP peak amplitudes were decreased after axotomy. This decrease seemed to be largely related to an absence of the largest EPSPs, since otherwise the EPSP distributions of normal and axotomized motoneurons showed considerable overlap. It is suggested that the observed decrease in PTP after axotomy is related to a change in synaptic release properties and not secondary to changes in the electrical properties of motoneurons. A previous analysis has suggested that axotomy causes an alteration of the distribution of passive electrical properties among motoneurons such that axotomized cells resemble normal high-resistance motoneurons. The present results suggest that axotomy may affect the distribution of Ia synaptic release properties in a similar manner, since PTP in axotomized motoneurons resembles that observed in normal high-resistance motoneurons. MH - Animal ; Anterior Horn Cells/PHYSIOLOGY ; Cats ; Cell Membrane/PHYSIOLOGY ; Electric Conductivity ; Membrane Potentials ; *Neural Transmission ; Neurons, Afferent/PHYSIOLOGY ; Spinal Cord/*PHYSIOLOGY ; Support, Non-U.S. Gov't ; Synapses/PHYSIOLOGY SO - J Neurophysiol 1986 Oct;56(4):1174-84 3 UI - 87054482 AU - Shin HK ; Kim J ; Nam SC ; Paik KS ; Chung JM TI - Spinal entry route for ventral root afferent fibers in the cat. AB - Twelve anesthetized and paralyzed cats were used to study the spinal entry routes of ventral root afferent fibers. In all animals, the spinal cord was transected at two different levels, L5 and S2. The L5 through S2 dorsal roots were cut bilaterally, making spinal cord segments L5-S2 neurally isolated from the body except for the L5-S2 ventral roots. From this preparation, a powerful excitation of the discharge rate of motor neurons and dorsal horn cells within the isolated spinal segments was observed after intraarterial injection of bradykinin (50 micrograms in 0.5 ml saline). This excitation of the spinal neurons can be considered the most convincing evidence of the potential physiologic role of the ventral root afferent fibers entering the spinal cord directly through the ventral root, because the apparent route of neuronal input from the periphery is through the ventral roots. However, additional control experiments conducted in the present study showed that the excitation persisted even after cutting all ventral roots within the isolated spinal segments, indicating that excitation was not mediated by the ventral roots. Furthermore, direct application of bradykinin on the dorsal surface of the spinal cord also increased the motoneuronal discharge rate, suggesting that excitation of spinal neurons produced by intraarterial injection of bradykinin is due to a direct action of bradykinin on the spinal cord. Thus, we provided an alternate explanation for the most convincing evidence indicating that physiologically important ventral root afferent fibers enter the spinal cord directly through the ventral root. Based on existing experimental evidence, it is likely that the majority of physiologically active ventral root afferent fibers travel distally toward the dorsal root ganglion and then enter the spinal cord through the dorsal root. MH - Action Potentials/DRUG EFFECTS ; Afferent Pathways/DRUG EFFECTS/ *PHYSIOLOGY ; Animal ; Bradykinin/PHARMACODYNAMICS ; Cats ; Female ; Ganglia, Spinal/PHYSIOLOGY ; Male ; Motor Neurons/DRUG EFFECTS/ *PHYSIOLOGY ; Neurons, Afferent/DRUG EFFECTS/PHYSIOLOGY ; Spinal Cord/ *PHYSIOLOGY ; Spinal Nerve Roots/*PHYSIOLOGY ; Support, U.S. Gov't, P.H.S. SO - Exp Neurol 1986 Dec;94(3):714-25 4 UI - 87027454 AU - Davies J ; Evans RH ; Herrling PL ; Jones AW ; Olverman HJ ; Pook P ; Watkins JC TI - CPP, a new potent and selective NMDA antagonist. Depression of central neuron responses, affinity for [3H]D-AP5 binding sites on brain membranes and anticonvulsant activity. AB - Properties of a new potent antagonist acting selectively at N-methyl-D-aspartate (NMDA) type excitatory amino acid receptors are described. This compound, 3-((+/-)-2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) is more potent than all previously reported NMDA antagonists in depressing mammalian spinal neuronal responses (cat and immature rat), in its affinity for [3H]D-AP5 (a radiolabelled NMDA antagonist) binding sites on rat brain membranes, and as an anticonvulsant in mice. MH - Animal ; *Anticonvulsants ; Aspartic Acid/*ANALOGS & DERIVATIVES/ ANTAGONISTS & INHIBITORS ; Binding Sites ; Brain/DRUG EFFECTS/METABOLISM/ *PHYSIOLOGY ; Cats ; Cell Membrane/METABOLISM ; Interneurons/PHYSIOLOGY ; Membrane Potentials/DRUG EFFECTS ; Mice ; Motor Neurons/PHYSIOLOGY ; Neurons/DRUG EFFECTS/*PHYSIOLOGY ; Piperazines/*PHARMACODYNAMICS ; Rats ; Spinal Cord/DRUG EFFECTS/*PHYSIOLOGY ; Support, Non-U.S. Gov't ; Valine/ *ANALOGS & DERIVATIVES/METABOLISM SO - Brain Res 1986 Sep 10;382(1):169-73 5 UI - 86297538 AU - Botterman BR ; Cope TC TI - Discharge properties of motoneurons supplying distal forelimb muscles in the cat. AB - Discharge properties of cat cervical motoneurons innervating distal forelimb muscles were investigated by intracellular current injection. Values for rheobase current, afterhyperpolarization duration and several measures of repetitive discharge characteristics were in most respects similar to those obtained for hindlimb motoneurons. MH - Action Potentials ; Animal ; Cats ; Electric Stimulation ; Forelimb/ *INNERVATION/PHYSIOLOGY ; Motor Neurons/CLASSIFICATION/*PHYSIOLOGY ; Muscles/*INNERVATION/PHYSIOLOGY ; Reaction Time/PHYSIOLOGY ; Spinal Cord/ *PHYSIOLOGY ; Ulnar Nerve/PHYSIOLOGY SO - Brain Res 1986 Jul 30;379(1):192-5 6 UI - 86297526 AU - Yamaguchi T TI - Descending pathways eliciting forelimb stepping in the lateral funiculus: experimental studies with stimulation and lesion of the cervical cord in decerebrate cats. AB - The funicular pathways that elicit forelimb stepping were investigated with stimulation and lesion of the cervical white matter in decerebrate cats with the lower thoracic cord transected. We localized cross-sectional areas where stimulation evoked rhythmic motor-nerve discharges imitating those of stepping (fictive locomotion) in the immobilized animal, and further examined whether or not lesions made in the corresponding areas abolished actual locomotor movements. Stimulation of the C3 lateral funiculus (LF) produced fictive locomotion in the ipsilateral forelimb. The effective areas of stimulation were located separately in the dorsolateral funiculus (DLF) and in the ventrolateral funiculus (VLF), while the VLF was more effective than the DLF. Effective stimuli were pulse trains with a frequency of about 30 Hz, with a rather wide pulse duration of about 0.5 ms. Blocking axonal conduction through the lower thoracic cord by cooling reproducibly facilitated fictive locomotion in both amplitude and frequency. In the lesion experiments, forelimb locomotor movements were elicited spontaneously or by stimulation of the mesencephalic locomotor region (MLR). The locomotor movements were abolished by complete lesions of the C2-C3 LFs on both sides, but these remained when either the DLF or the VLF was intact on one side. These findings together suggested that the descending pathways for the activation of the spinal locomotor network of the single forelimb are located ipsilaterally in the DLF as well as in the VLF. Both the DLF and the VLF pathways can initiate locomotion, while the VLF pathways have a higher potential for its initiation. Lesion experiments further showed that cats can walk with both forelimbs, even though the spinal locomotor network of the single forelimb was deprived of its main descending input by unilateral lesions of the LF. However, when the unilateral lesion extended to the medial part of the LF, the bilateral walking was abolished; the limb on the lesioned side showed only rhythmic extension movements without active flexion movements, which was out of phase with the stepping movements on the intact side. This finding suggested that the medial part of the LF is important for producing flexion movements during the swing phase of stepping. MH - Animal ; Cats ; Decerebrate State/*PHYSIOPATHOLOGY ; Efferent Pathways/ PHYSIOLOGY ; Electric Stimulation ; Evoked Potentials ; Forelimb/ *INNERVATION/PHYSIOLOGY ; Laterality/PHYSIOLOGY ; *Locomotion ; Motor Neurons/PHYSIOLOGY ; Spinal Cord/ANATOMY & HISTOLOGY/*PHYSIOLOGY SO - Brain Res 1986 Jul 30;379(1):125-36 7 UI - 86271071 AU - Schomburg ED ; Steffens H ; Warneke G TI - Functional organization of the spinal reflex pathways from forelimb afferents to hindlimb motoneurones in the cat. II. Conditions of the interneuronal connections. AB - The interneuronal conditions of the descending pathways from forelimb afferents to hindlimb motoneurones were investigated by testing spatial interactions in these pathways and between these pathways and segmental lumbar reflex pathways. In high spinal unanaesthetized cats hindlimb motoneurones were intracellularly recorded and spatial interactions were tested between effects evoked by stimulation of pairs of ipsi- and contralateral forelimb nerves or pairs of a forelimb and an ipsilateral hindlimb nerve. The excitatory and late inhibitory pathways from forelimb afferents projecting to most of the hindlimb motoneurone pools, showed an interactive pattern which was distinctly different to the fast inhibitory pathway projecting specifically from ipsilateral forelimb afferents to flexor digitorum and hallucis longus (FDHL) motoneurones. Stimulation of homonymous or heteronymous pairs of two forelimb nerves of both sides evoked generally a distinct spatial facilitation of the excitatory and late inhibitory effects, while the specific early IPSPs to FDHL motoneurones were not facilitated. Paired stimulation of two forelimb nerves of one side only produced spatial facilitation of EPSPs or late IPSPs if low strength stimuli were used, using higher strength which induced larger effects, generally caused occlusion instead. In case of large IPSPs this may be due to the vicinity to the equilibrium potential. Except for an inhibition of cutaneous reflex pathways, the spatial interaction of the excitatory and late inhibitory pathways onto segmental lumbar reflex pathways was weak and variable. The fast inhibitory pathway to FDHL motoneurones showed a partial spatial facilitatory interaction with lumbar reflex pathways from cutaneous and group II muscle afferents. The second IPSP wave evoked by this pathway was inhibited by antidromic stimulation of the ventral root L7S1 and of the alpha-efferents of the antagonistic peroneal nerve. From the results conclusions are drawn on the interneuronal organization of the descending pathways from forelimb afferents to hindlimb motoneurones. MH - Animal ; Cats ; Evoked Potentials ; Forelimb/INNERVATION ; Hindlimb/ INNERVATION ; Interneurons/PHYSIOLOGY ; Motor Neurons/*PHYSIOLOGY ; Neural Pathways/PHYSIOLOGY ; Neural Transmission ; Neurons, Afferent/ PHYSIOLOGY ; Reflex/*PHYSIOLOGY ; Spinal Cord/*PHYSIOLOGY ; Support, Non-U.S. Gov't SO - Brain Res 1986 Jun 11;375(2):280-90 8 UI - 86198850 AU - Munson JB ; Foehring RC ; Lofton SA ; Zengel JE ; Sypert GW TI - Plasticity of medial gastrocnemius motor units following cordotomy in the cat. AB - Experiments were performed in adult cats to determine the effects of lumbar cordotomy on synaptic potentials, motoneuron membrane electrical properties, muscle-unit contractile properties, and whole-muscle histochemical properties of a heterogeneous skeletal muscle. Medial gastrocnemius (MG) motor units were examined 1 wk to 7 mo following complete transection of the lumbar spinal cord (cordotomy). Motor units were classified on the basis of their contractile properties as type FF, FI, FR, or S (8, 68). Muscle fibers were classified as type FG, FOG, or SO on the basis of histochemical staining (59). Motoneuron electrical properties (axonal conduction velocity, action-potential amplitude, rheobase, input resistance, afterhyperpolarization), group I EPSPs, and muscle-unit contractile properties (unpotentiated and potentiated twitch, unfused and fused tetanus, fatigability) were measured. Reduced numbers of type FR motor units and increased numbers of types FI + FF motor units were found in electrophysiological experiments 2 wk to 7 mo following cordotomy. Corroborative data were obtained from histochemical studies of the same MG muscles. Electrical properties of the motoneurons of each motor-unit type were normal following cordotomy. The close correspondence between motoneuron electrical properties and muscle-unit contractile properties found in normal MG muscle (68) was preserved following cordotomy. Contractile strength of muscle units of all types was severely reduced following cordotomy; partial recovery occurred 4-7 mo following cordotomy. Cross-sectional area of muscle fibers was reduced at all times investigated (2 wk to 7 mo). In three cats, homonymous group Ia single-fiber-motoneuron EPSPs were studied 1 or 2 mo following cordotomy at spinal level L4-5 or L5. EPSP amplitude and afferent-to-motoneuron projection frequency were normal. In 12 other cats, composite heteronymous group I EPSPs were studied 2 wk to 7 mo following cordotomy at various levels. Amplitude of these EPSPs was increased, dependent upon level of cordotomy and postoperative time. Hypotheses concerning the influence of motoneurons on muscle, and of muscle on motoneurons, are presented as possible mechanisms whereby the close relation between motoneuron electrical and muscle-unit contractile properties is preserved in the face of redistributed motor-unit populations. MH - Afferent Pathways/PHYSIOLOGY ; Animal ; Cats ; Evoked Potentials ; Motor Neurons/*PHYSIOLOGY ; Muscles/CYTOLOGY/*INNERVATION ; *Neuronal Plasticity ; Spinal Cord/*PHYSIOLOGY ; Support, U.S. Gov't, Non-P.H.S. ; Support, U.S. Gov't, P.H.S. ; Synapses/PHYSIOLOGY SO - J Neurophysiol 1986 Apr;55(4):619-34 9 UI - 86170699 AU - Sedivec MJ ; Capowski JJ ; Mendell LM TI - Morphology of HRP-injected spinocervical tract neurons: effect of dorsal rhizotomy. AB - Twenty-five physiologically identified spinocervical tract (SCT) neurons in the sixth lumbar segment of the cat were filled with HRP by intracellular injection. All were reconstructed from sagittal sections using the camera lucida, and a subset (n = 18) was also reconstructed using a computer reconstruction system. Thirteen cells were in intact preparations, nine were in spared root preparations (L5, L6, S1, S2 cut; L7 spared), and three were in preparations with L5 through S2 cut. Analysis of the dendritic tree of these neurons revealed little change in gross morphology after partial deafferentation despite increased proportions sensitive to nociceptive input (Sedivec et al., 1983). The dendrites still largely respected the lamina II-III border, and relatively few dendrites were directed ventrally from the cell body, although the ratio of ventral to dorsal dendrites was greater than normal. The major change was an increase in surface area and volume caused by changes in diameter (but not length) of the dendrites. Larger-than-usual maximum branch order of individual dendritic trees of some cells was also observed after chronic deafferentation. Thus, SCT cells in deafferented segments do not undergo atrophy, but show, rather, limited signs of growth and the possibility of dendritic reorganization. We have also computed correlations between different parameters of these cells (cell body size, number and size of primary dendrites, total area and length of individual dendrites) and have found that, as in motoneurons, diameter of the primary dendrite measured 30 micron from the soma is significantly correlated with total dendritic surface area and length. SCT neurons tend to have more dendrites than spinal alpha-motoneurons, but total surface area is smaller for a given diameter of a proximal dendrite. MH - Animal ; Cats ; Computers ; Dendrites/CYTOLOGY ; Female ; Horseradish Peroxidase/METABOLISM ; Male ; Mathematics ; Motor Neurons/CYTOLOGY ; Neurons/*CYTOLOGY ; Spinal Nerve Roots/*PHYSIOLOGY ; Spinothalamic Tracts/ *CYTOLOGY ; Support, U.S. Gov't, P.H.S. SO - J Neurosci 1986 Mar;6(3):661-72 10 UI - 86170690 AU - Vanden Noven S ; Hamm TM ; Stuart DG TI - Partitioning of monosynaptic Ia excitatory postsynaptic potentials in the motor nucleus of the cat lateral gastrocnemius muscle. AB - Experiments were conducted to test the hypothesis that a partitioning of Ia monosynaptic excitatory postsynaptic potentials (Ia EPSPs) is present in motor nuclei supplying muscles with regions capable of different mechanical actions. Intracellular recordings of synaptic potentials were made in lateral gastrocnemius (LG) motoneurons in anesthetized low-spinal cats. The effects were tested of stimuli (group I range) to the four primary nerve branches of the LG nerve supplying muscle compartments LGm, LG1, LG2, and LG3 (terminology of English, Ref. 26) and the nerve to a heteronymous muscle, soleus. Stimulation of a given LG nerve branch produced monosynaptic Ia EPSPs of greater amplitude in "own-branch: motoneurons than "other-branch: cells. A significant partitioning of mean Ia EPSPs was found in three (LG1, LG2, LG3) out of the four homonymous pathways studied. An EPSP normalization (7) was performed to eliminate potential differences in cell type that might affect the amplitudes of the EPSPs between these four cell groups (e.g., differences in the number of cells supplying FF, FR, and S muscle units). This normalization confirmed that the partitioning of monosynaptic Ia inputs upon stimulation of LG1, LG2, and LG3 could not be attributed to differences in cell type. In addition, the effects of LGm stimulation were found to be significantly greater in the LGm motoneurons compared with the other cell groups. Heteronymous input (from soleus) to the LG motor nucleus showed some partitioned effects. Motoneurons innervating compartment LG2 received larger EPSPs from soleus than did the cells supplying compartments LG1, LG3, and LGm. The contributions of location specificity and species specificity (terminology of Scott and Mendell, Ref. 55) in the establishment of these Ia-afferent-motoneuronal connections were examined. Cell location sites within the spinal cord were consistent with location specificity making some contribution to the observed pattern of homonymous Ia connections. A more prominent role for species specificity was indicated by species-dependent differences in EPSP amplitude in pairs of LG motoneurons (e.g., LGm vs. LG2) at similar rostrocaudal locations upon stimulation of a given homonymous or heteronymous nerve/branch. MH - Afferent Pathways/PHYSIOLOGY ; Animal ; Cats ; Electric Stimulation ; Electrophysiology ; Evoked Potentials ; Models, Neurological ; Motor Neurons/*PHYSIOLOGY ; Muscles/*INNERVATION ; Review ; Spinal Cord/ PHYSIOLOGY ; Support, Non-U.S. Gov't ; Support, U.S. Gov't, P.H.S. ; Synapses/PHYSIOLOGY SO - J Neurophysiol 1986 Mar;55(3):569-86 11 UI - 86170681 AU - Shinoda Y ; Yamaguchi T ; Futami T TI - Multiple axon collaterals of single corticospinal axons in the cat spinal cord. AB - To investigate intraspinal branching patterns of single corticospinal neurons (CSNs), we recorded extracellular spike activities from cell bodies of 408 CSNs in the motor cortex in anesthetized cats and mapped the distribution of effective stimulating sites for antidromic activation of their terminal branches in the spinal gray matter. To search for all spinal axon branches belonging to single CSNs in the "forelimb area: of the motor cortex, we microstimulated the gray matter from the dorsal to the ventral border at 100-micron intervals at an intensity of 150-250 microA and systematically mapped effective stimulating penetrations at 1-mm intervals rostrocaudally from C3 to the most caudal level of their axons. From the depth-threshold curves, the comparison of the antidromic latencies of spikes evoked from the gray matter and the lateral funiculus, and the calculated conduction times of the collaterals, we could ascertain that axon collaterals were stimulated in the gray matter rather than stem axons in the corticospinal tract due to current spread. Virtually all CSNs examined in the forelimb area of the motor cortex had three to seven branches at widely separated segments of the cervical and the higher thoracic cord. In addition to terminating at the brachial segments, they had one to three collaterals to the upper cervical cord (C3-C4), where the propriospinal neurons projecting to forelimb motoneurons are located. About three quarters of these CSNs had two to four collaterals in C6-T1. This finding held true for both fast and slow CSNs. About one third of the CSNs in the forelimb area of the motor cortex projected to the thoracic cord below T3. These CSNs also sent axon collaterals to the cervical spinal cord. CSNs in the "hindlimb area: of the motor cortex had three to five axon branches in the lumbosacral cord. These branches were mainly observed at L4 and the lower lumbosacral cord. None of these CSNs had axon collaterals in the cervical cord. CSNs terminating at different segments of the cervical and the thoracic cord were distributed in a wide area of the motor cortex and were intermingled. To determine the detailed trajectory of single axon branches, microstimulation was made at a matrix of points of 100 or 200 micron at the maximum intensity of 30 microA, and their axonal trajectory was reconstructed on the basis of the location of low-threshold foci and the latency of antidromic spikes.(ABSTRACT TRUNCATED AT 400 WORDS) MH - Animal ; Axons/*PHYSIOLOGY/ULTRASTRUCTURE ; Cats ; Electric Stimulation ; Electrophysiology ; Evoked Potentials ; Interneurons/PHYSIOLOGY/ ULTRASTRUCTURE ; Motor Cortex/PHYSIOLOGY/ULTRASTRUCTURE ; Motor Neurons/ PHYSIOLOGY/ULTRASTRUCTURE ; Review ; Spinal Cord/*PHYSIOLOGY/ ULTRASTRUCTURE ; Support, Non-U.S. Gov't SO - J Neurophysiol 1986 Mar;55(3):425-48 12 UI - 86169025 AU - Wong-Riley MT ; Kageyama GH TI - Localization of cytochrome oxidase in the mammalian spinal cord and dorsal root ganglia, with quantitative analysis of ventral horn cells in monkeys. AB - The spinal cord and dorsal root ganglia of mice, rats, cats, squirrel monkeys, and macaque monkeys were examined at both the light and electron microscopic levels for cytochrome oxidase activity. A similar histochemical pattern prevailed in all of the species examined. While the spinal gray exhibited a heterogeneous but consistent distribution of the enzyme, the white matter was only lightly stained. Highly reactive neurons were either singly scattered or aggregated into discrete clusters. The dorsal nucleus of Clarke, the lateral cervical nucleus (cat), the intermediolateral cell columns of the thoracic and upper lumbar levels, and selected groups of ventral horn neurons formed moderate to darkly reactive cell clusters, whereas fusiform and multipolar cells of Waldeyer in the marginal layer, small fusiform neurons in the ventral gray, funicular cells in the white matter, and ventral horn neurons of varying sizes tended to stand out against the neuropil as singly reactive neurons. At the electron microscopic level, reactive neurons were characterized by a greater packing density of darkly reactive mitochondria, while lightly reactive ones had fewer mitochondria, most of which showed very little reaction product. Reactive mitochondria were also found in the neuropil, mainly in dendritic profiles and some axon terminals. Glial cells, in general, were not very reactive. Ventral horn neurons from three macaque monkeys were measured for somatic areas and optical densities of cytochrome oxidase reaction product. A total of 1,770 neurons from representative sections of the cervical, thoracic, lumbar, and sacral cords of these animals were analyzed. The results indicated that the distribution of cell sizes as well as optical densities at every level of the cord fell on a continuum. Analysis of the regression coefficients revealed that the slopes were negative for all levels, indicating that there was a general inverse relationship between cell size and optical densities. However, there were representations of dark, moderate, and lightly reactive neurons in all three size categories (large, medium, and small). Thus, the level of oxidative metabolism of ventral horn neurons cannot be correlated strictly with size, but it is likely to reflect their total synaptic and spontaneous activities. Neurons of the dorsal root ganglia likewise exhibited heterogeneous distribution of cell sizes and levels of enzyme reactivity, while satellite cells, in general, were only lightly reactive. As in the case of the ventral horn, representatives of dark, moderate, and light levels of reactivity occurred in every size category of neurons.(ABSTRACT TRUNCATED AT 400 WORDS) MH - Animal ; Cats ; Cytochrome Oxidase/*ANALYSIS ; Densitometry ; Ganglia, Spinal/*ENZYMOLOGY/ULTRASTRUCTURE ; Macaca fascicularis ; Macaca mulatta ; Mice ; Microscopy, Electron ; Motor Neurons/CLASSIFICATION/CYTOLOGY ; Neurons/*ENZYMOLOGY/ULTRASTRUCTURE ; Rats ; Spinal Cord/*ENZYMOLOGY/ ULTRASTRUCTURE ; Stains and Staining ; Support, U.S. Gov't, P.H.S. SO - J Comp Neurol 1986 Mar 1;245(1):41-61 13 UI - 86164763 AU - Henatsch HD ; Meyer-Lohmann J ; Windhorst U ; Schmidt J TI - Differential effects of stimulation of the cat's red nucleus on lumbar alpha motoneurones and their Renshaw cells. AB - The red nucleus region was stereotaxically stimulated with short trains of high-frequency alternating current pulses in anaesthetized cats. The effects were studied, in contralateral lumbar segments, on the responses of microrecorded individual Renshaw cells (RCs) to antidromic or orthodromic test shocks of ventral root or muscle nerve fibres. Monosynaptic reflexes (MRs) of their motoneurone pools were recorded from one of the cut lumbar ventral roots. Averages of 10-20 replicate test responses of the RC (converted into instantaneous frequency curves, IFCs) and of the MR shapes were computed and graphically displayed. 2. Orthodromic (afferent) test shocks induced simultaneously MRs as well as responses of a RC belonging to the same motor pool. From their paired records at systematically varied shock strengths, whole "linkage characteristics: of the relation between the two events could be obtained, representing the functional linkage from the motoraxon collaterals to the RC under study. The overall result of rubral conditioning was a change in the course of the characteristic, which indicated a reduction of this linkage (= relative inhibition of the RC against its recurrent input). 3. Sequential trials with test shocks of constant, submaximal strength were performed with 45 individual RCs. The clearest results were obtained with RC responses to antidromic ventral root shocks: 65% of the RCs were partially inhibited by rubral conditioning. Interposed minor facilitory subcomponents could be seen in the course of inhibited IFCs. Mixed sequences of manifest inhibitory/facilitory effects were observed in 11%; reversed sequences (facilitory/inhibitory) did not occur. A pure but weak facilitation was found in only one case, paralleled by an increase of the MR. RCs belonging to either extensor or flexor motor pools were affected about equally. A little over 20% of the tested RCs remained uninfluenced by rubral stimulation. 4. The MRs, induced by constant, submaximal, orthodromic test shocks, were usually enhanced with only few exceptions, by rubral stimulation. The effects on the orthodromic RC responses were mainly inhibitory, but could be more or less masked by the concurrent increase of the MR, providing a stronger recurrent input to the RC. Such inhibition could be uncovered, however, by observing the above described linkage change. 5. Variation of several parameters of rubral conditioning (train duration, timing of train with respect to test shock, strength of train) modified the inhibitory effects on antidromic RC responses to a certain extent without changing their principal character.(ABSTRACT TRUNCATED AT 400 WORDS) MH - Animal ; Brain Mapping ; Cats ; Electric Stimulation ; Evoked Potentials ; Extrapyramidal Tracts/PHYSIOLOGY ; Interneurons/PHYSIOLOGY ; Motor Neurons/PHYSIOLOGY ; Neural Inhibition ; Red Nucleus/*PHYSIOLOGY ; Reflex, Monosynaptic ; Spinal Cord/*PHYSIOLOGY ; Support, Non-U.S. Gov't SO - Exp Brain Res 1986;62(1):161-74 14 UI - 86136409 AU - Edgley S ; Jankowska E ; McCrea D TI - The heteronymous monosynaptic actions of triceps surae group Ia afferents on hip and knee extensor motoneurones in the cat. AB - Monosynaptic connections from the group Ia afferents of triceps surae onto quadriceps, anterior biceps and semimembranosus motoneurones have been demonstrated in the cat. They appear to be equivalent to those found between triceps surae and thigh muscles in man. MH - Animal ; Cats ; Comparative Study ; Evoked Potentials ; Leg ; Motor Neurons/*PHYSIOLOGY ; Muscles/*INNERVATION ; Neural Transmission ; Neurons, Afferent/PHYSIOLOGY ; Organ Specificity ; Spinal Cord/ *PHYSIOLOGY ; Support, Non-U.S. Gov't ; Synapses/PHYSIOLOGY SO - Exp Brain Res 1986;61(2):443-6 15 UI - 86136394 AU - Lipski J ; Bektas A ; Porter R TI - Short latency inputs to phrenic motoneurones from the sensorimotor cortex in the cat. AB - Short latency responses were recorded from C5 phrenic roots and intracellularly from phrenic motoneurones following stimulation of the pericruciate cortex or medullary pyramids in cats anaesthetized with Nembutal or chloralose-urethane. Focal stimulation of the cortical surface (single pulses, 0.5-2 ms, 0.3-8 mA) during inspiration evoked EPSPs (latency 4.7 +/- 1.7 ms, rise time 1.9 +/- 1.1 ms, amplitude 0.22 to 3.94 mV) in 42% of motoneurones studied (n = 107). The EPSPs were absent, or on average 60% smaller, following stimulation during expiration. In all but two motoneurones, during both inspiration and expiration, hyperpolarizing potentials were observed either following the initial depolarization or alone. They could be reversed by hyperpolarizing current or chloride injection. Stimulation of the pyramidal tract at mid medullary level (1 to 3 pulses, 0.2 ms) evoked short latency excitation in phrenic motoneurones only with currents of more than 200 microA. Smaller stimuli applied to the medial reticular formation above the pyramidal tract evoked excitation (onset latency 1.5-3.2 ms) in which the earliest part was probably monosynaptic. These results show that the corticospinal responses in phrenic motoneurones are both excitatory and inhibitory. They are not transmitted through the pyramidal tract and are at least disynaptic. Excitation evoked from the medullary pyramidal tract can be explained by current spread beyond the pyramidal tract fibres. MH - Animal ; Brain Mapping ; Cats ; Evoked Potentials ; Female ; Male ; Motor Cortex/*PHYSIOLOGY ; Motor Neurons/*PHYSIOLOGY ; Neural Inhibition ; Neural Transmission ; Phrenic Nerve/*PHYSIOLOGY ; Pyramidal Tracts/ PHYSIOLOGY ; Reaction Time/PHYSIOLOGY ; Reticular Formation/PHYSIOLOGY ; Somatosensory Cortex/*PHYSIOLOGY SO - Exp Brain Res 1986;61(2):280-90