Characteristics of spinal neurones responding to cutaneous myelinated and unmyelinated fibres*

Gregor, Michael; Zimmermann, M.

doi:10.1113/jphysiol.1972.sp009767

Cited by 87 publications

(10 citation statements)

References 34 publications

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“…The central latency of the earliest response in these neurones varied widely but was always greater than 2.3 ms (4.72 + 0.36 ms, n = 20). These latencies are too long to be mediated monosynaptically (Eccles, Fatt & Landgren, 1956;Coombs et al, 1956;Eccles, Kostyuk & Schmidt, 1962;Gregor & Zimmermann, 1972). Unlike responses evoked monosynaptically, those evoked polysynaptically invariably consisted of more than one spike and failed to follow high frequencies of stimulation.…”

Section: Resultsmentioning

confidence: 99%

Selective Depression of Synaptic Excitation in Cat Spinal Neurones by Baclofen: An Iontophoretic Study

Davies

1981

British J Pharmacology

244

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Brunswick Square, London WC1N lAX 1 The effects of baclofen have been examined on responses of neurones in the spinal cord of the anaesthetized cat to stimulation of appropriate synaptic pathways, acetylcholine and a range of amino acid excitants. Baclofen and excitant substances were administered by standard microiontophoretic techniques. 2 Small ejecting currents of baclofen (<10 nA) depressed non-cholinergic, excitatory, synaptic responses evoked by stimulation of dorsal roots or muscle or cutaneous afferents. Excitatory monosynaptic responses were particularly sensitive to the depressant action of baclofen. 3 Spontaneous firing in neurones was sometimes reduced in parallel with synaptic excitatory responses, but synaptically evoked inhibition was unaffected and ventral root evoked excitation of Renshaw cells was either unaffected or enhanced by baclofen. 4 Ejecting currents of baclofen which markedly depressed excitatory synaptic responses either had no effect or minimal depressant effects on responses induced by iontophoretically administered acetylcholine and excitant amino acids. However, relatively large currents of baclofen (e.g. 20 to 40 nA) reduced excitatory responses to exogenously administered excitants. 5 It is suggested that baclofen depresses (a) synaptic response by an action on excitatory nerve terminals and (b) responses to exogenous excitants via a postsynaptic action.6 Comparison of baclofen with a number of other substances indicates that the depression of noncholinergic, excitatory, synaptic responses is unlikely to involve an interaction of this agent with receptors for monoamines, 5-hydroxytryptamine or the inhibitory amino acids, y-aminobutyric acid and glycine.

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Section: Resultsmentioning

confidence: 99%

Selective Depression of Synaptic Excitation in Cat Spinal Neurones by Baclofen: An Iontophoretic Study

Davies

1981

British J Pharmacology

244

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“…These findings can be contrasted with dorsal horn interneurones in the spinal cord, where, in addition to selective excitation by myelinated or non-myelinated fibres a high proportion show convergent effects from both myelinated and non-myelinated afferent fibres (e.g. Christenson & Perl, 1970;Gregor & Zimmerman, 1972;Kumazawa & Perl, 1976).…”

Section: Discussionmentioning

confidence: 99%

Neurones in the brain stem of the cat excited by vagal afferent fibres from the heart and lungs.

Bennett¹,

Goodchild²,

Kidd³

et al. 1985

The Journal of Physiology

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Extracellular recordings were made from 164 neurones in the nucleus tractus solitarius and dorsal motor vagal nucleus of the chloralose-anaesthetized cat. 139 neurones were excited synaptically and 25 non-synaptically by electrical stimulation of cardiac and pulmonary vagal branches. Synaptically excited neurones fall into two populations, one activated solely by myelinated afferent fibres and a second activated solely by non-myelinated afferent fibres. 94 neurones were synaptically excited by afferent fibres in a single vagal branch while 45 were excited by stimulation of two or three branches. Neurones responding to volleys in myelinated afferent fibres were located in both medial and lateral regions of the nucleus tractus solitarius whilst those excited by non-myelinated afferent fibres were restricted to the medial region. Consistent differences in the locations of neurones excited by stimulation of either cardiac or pulmonary or by single or several branches could not be distinguished.

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“…Not all deep dorsal horn neurons receive C‐nociceptor drive – reports suggest that 51–88% of dorsal horn neurons are C+ve depending on species (rat and cat, lower end of range from cat; Gregor & Zimmermann, ; Menetrey et al . ; Waters & Lumb, ).…”

Section: Discussionmentioning

confidence: 99%

Periaqueductal grey cyclooxygenase‐dependent facilitation of C‐nociceptive drive and encoding in dorsal horn neurons in the rat

Leith

Wilson

You

et al. 2014

The Journal of Physiology

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Key pointsA- and C-nociceptors make different contributions to pain. They signal fast and slow pain, respectively, and C-nociceptors drive central sensitisation.Cyclooxygenase-1 (COX-1)-dependent descending facilitation from the periaqueductal grey (PAG) affects C-nociceptor spinal reflexes, but leaves A-nociceptor reflexes largely untouched. We studied the responses of spinal wide dynamic-range dorsal horn neurons to A- and C-nociceptor stimulation before and after COX-1 inhibition in the PAG. Inhibition of COX-1 descending facilitation disrupted the neuronal encoding of C-nociceptor information, but left the encoding of A-nociceptor information untouched. Inhibition of COX-1-dependent descending facilitation increased the activation threshold of wide dynamic range neurons to both A- and C-nociceptor input. The COX-dependent descending system from the PAG can therefore control the amount of C-nociceptor information reaching the CNS (slow, burning, aching, debilitating pain) without affecting the protective A-nociceptor information (sharp, well-localised, protective pain). AbstractThe experience of pain is strongly affected by descending control systems originating in the brainstem ventrolateral periaqueductal grey (VL-PAG), which control the spinal processing of nociceptive information. A- and C-fibre nociceptors detect noxious stimulation, and have distinct and independent contributions to both the perception of pain quality (fast and slow pain, respectively) and the development of chronic pain. Evidence suggests a separation in the central processing of information arising from A- vs. C-nociceptors; for example, inhibition of the cyclooxygenase-1 (COX-1)–prostaglandin system within the VL-PAG alters spinal nociceptive reflexes evoked by C-nociceptor input in vivo via descending pathways, leaving A-nociceptor-evoked reflexes largely unaffected. As the spinal neuronal mechanisms underlying these different responses remain unknown, we determined the effect of inhibition of VL-PAG COX-1 on dorsal horn wide dynamic-range neurons evoked by C- vs. A-nociceptor activation. Inhibition of VL-PAG COX-1 in anaesthetised rats increased firing thresholds of lamina IV–V wide dynamic-range dorsal horn neurons in response to both A- and C-nociceptor stimulation. Importantly, wide dynamic-range dorsal horn neurons continued to faithfully encode A-nociceptive information, even after VL-PAG COX-1 inhibition, whereas the encoding of C-nociceptor information by wide dynamic-range spinal neurons was significantly disrupted. Dorsal horn neurons with stronger C-nociceptor input were affected by COX-1 inhibition to a greater extent than those with weak C-fibre input. These data show that the gain and contrast of C-nociceptive information processed in individual wide dynamic-range dorsal horn neurons is modulated by prostanergic descending control mechanisms in the VL-PAG.

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Characteristics of spinal neurones responding to cutaneous myelinated and unmyelinated fibres*

Cited by 87 publications

References 34 publications

Selective Depression of Synaptic Excitation in Cat Spinal Neurones by Baclofen: An Iontophoretic Study

Selective Depression of Synaptic Excitation in Cat Spinal Neurones by Baclofen: An Iontophoretic Study

Neurones in the brain stem of the cat excited by vagal afferent fibres from the heart and lungs.

Periaqueductal grey cyclooxygenase‐dependent facilitation of C‐nociceptive drive and encoding in dorsal horn neurons in the rat

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