Information processed by dorsal horn spinocerebellar tract neurones in the cat (original) (raw)
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The Journal of physiology, 1988
1. In chloralose-anaesthetized cats single-unit microelectrode recordings were made from axons in the dorsal columns, at the lumbar level, identified as belonging to the postsynaptic dorsal column (PSDC) system. 2. Excitatory and inhibitory receptive field arrangements of a sample of seventy-five PSDC neurones were examined in detail using natural cutaneous stimuli. 3. The sample was characterized by a high degree of convergent input: 80% of units were activated by both light tactile and noxious mechanical stimuli and more than half of those examined were excited by noxious radiant heat. In addition, three-quarters of the units had inhibitory receptive fields on the ipsilateral limb. 4. Twenty-three units (27%) were influenced by input from areas of both hairy and glabrous skin covering the foot and distal limb. Neurones in this group had complex receptive fields, many of which occupied several discontinuous areas of skin. Background and evoked activity of these units could frequent...
The Journal of Physiology, 1984
1. Previous studies of input on to spinocervical tract neurones have been extended by investigating the post-synaptic actions of non-cutaneous afferent fibres and of descending tracts on to these neurones, using intracellular recording. In particular, actions of group II muscle, joint and Pacinian afferent fibres and rubro-and corticospinal tract fibres were investigated. 2. Group II muscle afferent fibres evoked excitation and inhibition at a minimal latency compatible with a disynaptic linkage. Increasing the stimulus strength to include group III afferent fibres enhanced these post-synaptic actions only modestly. Inhibition was evoked less frequently and/or required trains of stimuli. 3. Weak stimulation of the interosseous nerve evoked short latency (disynaptic) inhibition or excitation, the latter less frequently. Post-synaptic potentials evoked below threshold for group III afferent fibres of the interosseous nerve are attributed to the actions of Pacinian corpuscles. 4. Low threshold joint afferent fibres evoked excitation at short latency. Higher threshold joint afferent fibres usually evoked inhibition at longer latency, although high threshold excitation was sometimes observed. 5. Stimulation of the pyramidal tract evoked constant latency, unitary e.p.s.p.s which followed high frequencies. The evidence suggests that such e.p.s.p.s are evoked monosynaptically. Polysynaptic excitation and inhibition were also observed. 6. No convincing evidence could be found of actions evoked directly by the rubrospinal tract, although actions mediated via other descending systems could be induced from the red nucleus. 7. A large degree of convergence was seen from different peripheral and descending systems on to individual neurones.
Synaptic connections from large muscle afferents to the motoneurons of various leg muscles in man
Experimental Brain Research, 1984
Cross-correlations between stimuli delivered to peripheral nerves and the discharges of single, voluntarily activated, motor units can provide information about facilitatory and inhibitory projections to single spinal motoneurons in man. The projection frequency, under the given circumstances, of a facilitatory or inhibitory pathway can be obtained from the proportion of the sampled motor units of a given muscle showing the facilitatory or inhibitory effect. Deductions about the shape and relative amplitude of the underlying post-synaptic potentials can be made from the profile of the changes in firing probability. This technique has been used to explore the projections of low threshold muscle afferents to motoneurons of various leg muscles in man. Homonymous facilitation was demonstrated to all the sampled motor unit s of soleus (SOL), medial gastrocnemius (MG), tibialis anterior (TA) and vastus medialis (VM) and is presumed to represent the effects of the composite muscle spindle group Ia EPSP. Heteronymous facilitation was demonstrated between certain synergists. The projection frequency was less and the magnitude of the change in firing probability was smaller than for homonymous facilitation. SOL motoneurons, however, were not facilitated from low threshold afterents in the medial gastrocnemius nerve. Reciprocal inhibition was demonstrated between certain antagonists. The majority of the sampled motor uni.ts of SOL, however, were facilitated from low threshold afferents in the common peroneal nerve. The threshold for this facilitation was higher than for the homonymous facilitation elicited from this nerve and thus a different class of afferents and/or intercalated interneurons may be involved. There are projections across the knee joint in man. Motor units in vastus medialis (VM) were facilitated from low threshold Offprint requests to: P. Ashby (address see above) afferents in the common peroneal nerve. It is likely that these reflex connections, which differ from those in other species, reflect the functional relationships between various lower limb muscles in man.
Brain Research, 1989
Premotor neurones mediating skin reflex actions onto cat forelimb motoneurones at T~ were identified by observing their monosynaptic effects on motoneurones by means of spike-triggered averaging. Both excitatory and inhibitory premotor neurones, with mono-or polysynaptic inputs from skin afferents, were identified at C7 to rostrai Ca, and were found mostly in laminae V-VI. They received excitatory inputs from corticospinal and rubrospinal tract fibres.
Reflex patterns in postganglionic neurons supplying skin and skeletal muscle of the rat hindlimb
Journal of neurophysiology, 1994
1. Reflex patterns were analyzed in spontaneously active postganglionic vasoconstrictor neurons supplying skeletal muscle [muscle vasoconstrictor (MVC) neurons] and hairy skin [cutaneous vasoconstrictor (CVC) neurons] of the rat hindlimb. Postganglionic activity was recorded from single units and from filaments containing the axons of several spontaneously active neurons (multiunit preparations). The animals were freely breathing or artificially ventilated and maintained, in different experiments, under three different types of anesthesia (pentobarbital, chloralose, urethan). Reflexes were elicited by stimulation of arterial baroreceptors, chemoreceptors, cutaneous nociceptors, and cold receptors and visceral receptors from urinary bladder and colon. 2. Spontaneous activity of single postganglionic neurons ranged from 0.3 to 3.6 imp/s (median 1.15 imp/s and 1.0 imp/s in MVC and CVC neurons, respectively). Postganglionic axons conducted at 0.56 +/- 0.15 m/s (mean +/- SD, MVC neurons)...
Neuroscience Research, 2000
Effects of noxious skin stimulation (central foot pad and foot dorsum) by radiant heat were tested on neurones of ascending tracts with a main input from non-nociceptors. The dominating effect on ventral spinocerebellar tract neurones was a depression (mainly from the pad). Responses of spinocervical tract neurones were either facilitated (predominantly from the foot dorsum) or depressed (predominantly from the pad). The dominating effect on neurones tentatively classified as dorsal horn dorsal spinocerebellar tract neurones was facilitatory from both skin areas. Similar effects were evoked by selective actions of C-fibres when A-delta fibres were blocked by TTX.
Journal of Neurophysiology, 2012
We have shown for the first time that single cutaneous afferents in the foot dorsum have significant reflex coupling to motoneurons supplying muscles in the upper limb, particularly posterior deltoid and triceps brachii. These observations strengthen what we know from whole nerve stimulation, that skin on the foot and ankle can contribute to the modulation of interlimb muscles in distant innervation territories. The current work provides evidence of the mechanism behind the reflex, where one single skin afferent can evoke a reflex response, rather than a population. Nineteen of forty-one (46%) single cutaneous afferents isolated in the dorsum or plantar surface of the foot elicited a significant modulation of muscle activity in the upper limb. Identification of single afferents in this reflex indicates the strength of the connection and, ultimately, the importance of foot skin in interlimb coordination. The median response magnitude was 2.29% of background EMG, and the size of the e...
Characterization of cutaneous and articular sensory neurons
Background: A wide range of stimuli can activate sensory neurons and neurons innervating specific tissues often have distinct properties. Here, we used retrograde tracing to identify sensory neurons innervating the hind paw skin (cutaneous) and ankle/knee joints (articular), and combined immunohistochemistry and electrophysiology analysis to determine the neurochemical phenotype of cutaneous and articular neurons, as well as their electrical and chemical excitability. Results: Immunohistochemistry analysis using RetroBeads as a retrograde tracer confirmed previous data that cutaneous and articular neurons are a mixture of myelinated and unmyelinated neurons, and the majority of both populations are peptidergic. In whole-cell patch-clamp recordings from cultured dorsal root ganglion neurons, voltage-gated inward currents and action potential parameters were largely similar between articular and cutaneous neurons, although cutaneous neuron action potentials had a longer half-peak duration (HPD). An assessment of chemical sensitivity showed that all neurons responded to a pH 5.0 solution, but that acid-sensing ion channel (ASIC) currents, determined by inhibition with the nonselective acid-sensing ion channel antagonist benzamil, were of a greater magnitude in cutaneous compared to articular neurons. Forty to fifty percent of cutaneous and articular neurons responded to capsaicin, cinnamaldehyde, and menthol, indicating similar expression levels of transient receptor potential vanilloid 1 (TRPV1), transient receptor potential ankyrin 1 (TRPA1), and transient receptor potential melastatin 8 (TRPM8), respectively. By contrast, significantly more articular neurons responded to ATP than cutaneous neurons. Conclusion: This work makes a detailed characterization of cutaneous and articular sensory neurons and highlights the importance of making recordings from identified neuronal populations: sensory neurons innervating different tissues have subtly different properties, possibly reflecting different functions.
Neuroscience Letters, 1987
Extraccllular and intracellular recordings were made from antidromically identilied spinoccrvical tract (SCT) cells in the medial part of the lumbosacral dorsal horn in anesthetized cats. The Io~ threshold mechanoreceplivc ticlds (RFs) of 18 cells were mapped during extracellular recording, and for 15 the R F included an area of glabrous skin. lntracellular recordings were made from 6 of these during electrical microstimulation of glabrous skin and all showed excitatory postsynaptic potentials at latencies consistenl with conduction over group II primary afferent fibers. The distance fronl lhc medial border of Ihe dorsal horn of the recording loci of 12 cells. 4 of which were injected with horseradish pcroxidase, was measured. 11 is concluded that some medially situated S('T cells receive excitatory input from low threshold group 11 primary afferent fibers from glabrous skin.
The Journal of Physiology, 1979
The synaptic input to ascending tract cells with axons in the dorsal columns was investigated using intracellular recording. 2. E.p.s.p.s evoked by stimulation of the lateral funiculus were analysed to test for the possibility of collateral connexions between spino-cervical tract cells and dorsal column cells. Three groups of fibres were found to contribute to such e.p.s.p.s: fibres which terminated or originated between spinal segments C3-4 and C1, or Th9 and C3-4 and cortico-spinal tract fibres. The latencies and thresholds of e.p.s.p.s evoked by stimulation of the first group of fibres were compatible with their origin via axon collaterals of spino-cervical tract cells. The occurrence of these e.p.s.p.s in dorsal column cells which were disynaptically excited from cutaneous afferents further corroborated this possibility. 3. E.p.s.p.s of specifically cervical origin were also found in some other neurones in the dorsal horn, probably segmental interneurones, but were absent in spinocervical tract cells. 4. Convergence of group I muscle afferents (possibly both group Ia and group Ib) and cutaneous afferents was found in about 50 % of the dorsal column cells. The shortest latency e.p.s.p.s from cutaneous and group I afferents were evoked with segmental delays indicating monosynaptic and disynaptic coupling. 5. I.p.s.p.s were evoked from cutaneous and group I muscle afferents in either the same or different nerves as those from which the e.p.s.p.s were elicited. Excitatory potentials were, however, dominating.