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Betelli C, MacDermott AB, Bardoni R. Transient, activity dependent inhibition of transmitter release from low threshold afferents mediated by GABAA receptors in spinal cord lamina III/IV. Mol Pain 2015; 11:64. [PMID: 26463733 PMCID: PMC4605127 DOI: 10.1186/s12990-015-0067-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 10/06/2015] [Indexed: 12/20/2022] Open
Abstract
Background Presynaptic GABAA receptors (GABAARs) located on central terminals of low threshold afferent fibers are thought to be involved in the processing of touch and possibly in the generation of tactile allodynia in chronic pain. These GABAARs mediate primary afferent depolarization (PAD) and modulate transmitter release. The objective of this study was to expand our understanding of the presynaptic inhibitory action of GABA released onto primary afferent central terminals following afferent stimulation. Results We recorded evoked postsynaptic excitatory responses (eEPSCs and eEPSPs) from lamina III/IV neurons in spinal cord slices from juvenile rats (P17–P23, either sex), while stimulating dorsal roots. We investigated time and activity dependent changes in glutamate release from low threshold A fibers and the impact of these changes on excitatory drive. Blockade of GABAARs by gabazine potentiated the second eEPSC during a train of four afferent stimuli in a large subset of synapses. This resulted in a corresponding increase of action potential firing after the second stimulus. The potentiating effect of gabazine was due to inhibition of endogenously activated presynaptic GABAARs, because it was not prevented by the blockade of postsynaptic GABAARs through intracellular perfusion of CsF. Exogenous activation of presynaptic GABAARs by muscimol depressed evoked glutamate release at all synapses and increased paired pulse ratio (PPR). Conclusions These observations suggest that afferent driven release of GABA onto low threshold afferent terminals is most effective following the first action potential in a train and serves to suppress the initial strong excitatory drive onto dorsal horn circuitry.
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Affiliation(s)
- Chiara Betelli
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Via Campi, 287, 41125, Modena, Italy.
| | - Amy B MacDermott
- Departments of Physiology and Cellular Biophysics, Neuroscience, Columbia University, 630 W. 168th Street, New York, NY, 10032, USA.
| | - Rita Bardoni
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Via Campi, 287, 41125, Modena, Italy.
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Toyota M, Gilroy S. Gravitropism and mechanical signaling in plants. AMERICAN JOURNAL OF BOTANY 2013; 100:111-25. [PMID: 23281392 DOI: 10.3732/ajb.1200408] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Mechanical stress is a critical signal affecting morphogenesis and growth and is caused by a large variety of environmental stimuli such as touch, wind, and gravity in addition to endogenous forces generated by growth. On the basis of studies dating from the early 19th century, the plant mechanical sensors and response components related to gravity can be divided into two types in terms of their temporal character: sensors of the transient stress of reorientation (phasic signaling) and sensors capable of monitoring and responding to the extended, continuous gravitropic signal for the duration of the tropic growth response (tonic signaling). In the case of transient stress, changes in the concentrations of ions in the cytoplasm play a central role in mechanosensing and are likely a key component of initial gravisensing. Potential candidates for mechanosensitive channels have been identified in Arabidopsis thaliana and may provide clues to these rapid, ionic gravisensing mechanisms. Continuous mechanical stress, on the other hand, may be sensed by other mechanisms in addition to the rapidly adapting mechnaosensitive channels of the phasic system. Sustaining such long-term responses may be through a network of biochemical signaling cascades that would therefore need to be maintained for the many hours of the growth response once they are triggered. However, classical physiological analyses and recent simulation studies also suggest involvement of the cytoskeleton in sensing/responding to long-term mechanoresponse independently of the biochemical signaling cascades triggered by initial graviperception events.
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Affiliation(s)
- Masatsugu Toyota
- Department of Botany, University of Wisconsin, Birge Hall, 430 Lincoln Drive, Madison, Wisconsin 53706, USA
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Abstract
Presynaptic inhibition is one of many areas of neurophysiology in which Sir John Eccles did pioneering work. Frank and Fuortes first described presynaptic inhibition in 1957. Subsequently, Eccles and his colleagues characterized the process more fully and showed its relationship to primary afferent depolarization. Eccles' studies emphasized presynaptic inhibition of the group Ia monosynaptic reflex pathway but also included group Ib, II and cutaneous afferent pathways, and the dorsal column nuclei. Presynaptic inhibition of the group Ia afferent pathway was demonstrated by depression of monosynaptic excitatory postsynaptic potentials and inhibition of monosynaptic reflex discharges. Primary afferent depolarization was investigated by recordings of dorsal root potentials, dorsal root reflexes, cord dorsum and spinal cord field potentials, and tests of the excitability of primary afferent terminals. Primary afferent depolarization was proposed to result in presynaptic inhibition by reducing the amplitude of the action potential as it invades presynaptic terminals. This resulted in less calcium influx and, therefore, less transmitter release. Presynaptic inhibition and primary afferent depolarization could be blocked by antagonists of GABA(A) receptors, implying a role of interneurons that release gamma aminobutyric acid in the inhibitory circuit. The reason why afferent terminals were depolarized was later explained by a high intracellular concentration of Cl(-) ions in primary sensory neurons. Activation of GABA(A) receptors opens Cl(-) channels, and Cl(-) efflux results in depolarization. Another proposed mechanism of depolarization was an increase in extracellular concentration of K(+) following neural activity. Eccles' work on presynaptic inhibition has since been extended in a variety of ways.
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Affiliation(s)
- William D Willis
- Department of Neuroscience and Cell Biology, The University of Texas Medical Branch, Galveston, 77555-1069, USA.
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Hwang JH, Hwang KS, Kim JU, Choi IC, Park PH, Han SM. The interaction between intrathecal neostigmine and GABA receptor agonists in rats with nerve ligation Injury. Anesth Analg 2001; 93:1297-303. [PMID: 11682418 DOI: 10.1097/00000539-200111000-00054] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
UNLABELLED Nerve ligation injury may produce a pain syndrome that includes tactile allodynia. Reversal effects on tactile allodynia have been demonstrated after the intrathecal administration of gamma-aminobutyric acid (GABA) receptor agonists or cholinesterase inhibitors in rats. We examined the drug interactions between neostigmine and muscimol or baclofen in a rat model of nerve ligation injury. Rats were prepared with tight ligation of the left L5-6 spinal nerves and chronic intrathecal catheter implantation. Tactile allodynia was measured by applying von Frey filaments ipsilateral to the lesioned hindpaw. Thresholds for paw withdrawal were assessed. Neostigmine (0.3-10 microg), muscimol (0.1-10 microg), and baclofen (0.1-3.0 microg) were administered to obtain the dose-response curve and the 50% effective dose (ED(50)). Fractions of ED(50) values were administered intrathecally to establish the ED(50)s of drug combinations (neostigmine-muscimol and neostigmine-baclofen). The drug interactions were performed. Intrathecal neostigmine, muscimol, baclofen, and their combinations produced a dose-dependent increase in withdrawal threshold of the lesioned hindpaw. Both analyses revealed a synergistic interaction for the neostigmine-muscimol combination, whereas the effect of the neostigmine-baclofen combination was additive. These results suggest that the activation of both muscarinic and GABA(A) receptors is required for synergistic interaction. IMPLICATIONS This study indicates that drug interaction is synergistic for the neostigmine-muscimol combination, whereas the effect of the neostigmine-baclofen combination is additive. In a rat model of nerve ligation injury, neostigmine, muscimol, baclofen, and their combinations provide an antagonism on touch-evoked allodynia at the spinal level.
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Affiliation(s)
- J H Hwang
- Department of Anesthesiology, University of Ulsan, College of Medicine, Asan Medical Center, Seoul, Korea.
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Perrier JF, Lamotte D'Incamps B, Kouchtir-Devanne N, Jami L, Zytnicki D. Effects on peroneal motoneurons of cutaneous afferents activated by mechanical or electrical stimulations. J Neurophysiol 2000; 83:3209-16. [PMID: 10848541 DOI: 10.1152/jn.2000.83.6.3209] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The postsynaptic potentials elicited in peroneal motoneurons by either mechanical stimulation of cutaneous areas innervated by the superficial peroneal nerve (SP) or repetitive electrical stimulation of SP were compared in anesthetized cats. After denervation of the foot sparing only the territory of SP terminal branches, reproducible mechanical stimulations were applied by pressure on the plantar surface of the toes via a plastic disk attached to a servo-length device, causing a mild compression of toes. This stimulus evoked small but consistent postsynaptic potentials in every peroneal motoneuron. Weak stimuli elicited only excitatory postsynaptic potentials (EPSPs), whereas increase in stimulation strength allowed distinction of three patterns of response. In about one half of the sample, mechanical stimulation or trains of 20/s electric pulses at strengths up to six times the threshold of the most excitable fibers in the nerve evoked only EPSPs. Responses to electrical stimulation appeared with 3-7 ms central latencies, suggesting oligosynaptic pathways. In another, smaller fraction of the sample, inhibitory postsynaptic potentials (IPSPs) appeared with an increase of stimulation strength, and the last fraction showed a mixed pattern of excitation and inhibition. In 24 of 32 motoneurons where electrical and mechanical effects could be compared, the responses were similar, and in 6 others, they changed from pure excitation on mechanical stimulation to mixed on electrical stimulation. With both kinds of stimulation, stronger stimulations were required to evoke inhibitory postsynaptic potentials (IPSPs), which appeared at longer central latencies than EPSPs, indicating longer interneuronal pathways. The similarity of responses to mechanical and electrical stimulation in a majority of peroneal motoneurons suggests that the effects of commonly used electrical stimulation are good predictors of the responses of peroneal motoneurons to natural skin stimulation. The different types of responses to cutaneous afferents from SP territory reflect a complex connectivity allowing modulations of cutaneous reflex responses in various postures and gaits.
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Affiliation(s)
- J F Perrier
- Centre National de la Recherche Scientifique EP 1848, Université René Descartes, Unite de Formation et de Recherche Biomédicale, 75270 Paris 06, France
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Gossard JP, Cabelguen JM, Rossignol S. Phase-dependent modulation of primary afferent depolarization in single cutaneous primary afferents evoked by peripheral stimulation during fictive locomotion in the cat. Brain Res 1990; 537:14-23. [PMID: 2085768 DOI: 10.1016/0006-8993(90)90334-8] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Previous results from our laboratory have shown with intra-axonal recordings that hindfoot cutaneous primary afferents are subjected to rhythmic depolarizations during fictive locomotion (L-PAD) suggesting that cutaneous presynaptic mechanisms are activated by the central locomotor program. In this study, we examined the transmission in pathways responsible for primary afferent depolarizations (PAD) of cutaneous fibres during spontaneous fictive locomotion in decorticate cats and in spinal cats injected with nialamide and L-DOPA. PADs were evoked (E-PADs) by electrical stimulation of peripheral nerves and recorded intra-axonally with micropipettes in identified superficialis peroneal (SP; n = 7) and tibialis posterior (TP; n = 17) cutaneous primary afferents. Results showed that the amplitude of E-PADs, which were superimposed on the L-PAD, was deeply modulated throughout the locomotor cycle; decreasing to reach a minimum during the flexor phase and increasing to a maximum during the extensor phase. The results were not statistically different in fibres of the two nerves and in both types of preparation. The amplitude of E-PADs was always maximum during the extensor phase whether there was a large L-PAD or not during that phase. This suggests that the presynaptic mechanisms activated by central locomotor networks (L-PAD) and those activated by peripheral inputs (E-PAD) may in part be controlled differently. The results thus show that the transmission in PAD pathways activated by cutaneous inputs is phasically modulated by the central pattern generator for locomotion. This strongly suggests that the presynaptic inhibition in cutaneous fibres evoked by the movement-related feedback during real locomotion could be similarly modulated.
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Affiliation(s)
- J P Gossard
- Centre de Recherche en Sciences Neurologiques, Faculté de Médecine, Université de Montréal, Que., Canada
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Salter MW, Henry JL. Physiological characteristics of responses of wide dynamic range spinal neurones to cutaneously applied vibration in the cat. Brain Res 1990; 507:69-84. [PMID: 2302582 DOI: 10.1016/0006-8993(90)90524-f] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Extracellular single-unit recordings were made from wide dynamic range neurones in the lumbar dorsal horn of anaesthetized or decerebrated cats. Vibration applied to the skin at a frequency of 80 Hz could evoke 3 distinct types of response--excitation, depression or a biphasic response consisting of excitation followed by depression. By applying vibration at different sites, a given neurone was found to show more than one type of response. Parametric studies of the depressant and biphasic responses were made because previous studies indicated that adenosine mediates the depression in these types of response. Thus, amplitude- and frequency-response relationships were determined at individual stimulation sites: amplitude was varied from 0.001 to 1.0 mm (frequency, 80 Hz) and the frequencies studied were 10, 20, 40, 80, 120 and 240 Hz (amplitude, 0.15 mm). Vibration at amplitudes greater than 0.15 mm caused a decrease in the rate of discharge during the period of stimulation, the magnitude of this decrease varying directly with amplitude; at amplitudes of 0.15 mm and less vibration had no statistically significant effect. With regard to the frequency-response relationship, a decrease in discharge rate occurred at frequencies of 120 and 240 Hz, with the more pronounced effect at 240 Hz; excitation occurred at 40 Hz and there was no statistically significant effect at other frequencies. Amplitude- and frequency-response relationships for the depressant and the biphasic responses were analyzed separately. In the case of depressant responses, the magnitude was monotonically related to the amplitude of stimulation and depression occurred only at frequencies of 80 Hz or greater, with higher frequencies being more effective. The biphasic responses appeared to consist of 2 subtypes termed biphasic-1 and biphasic-2 responses. For biphasic-1 responses, the amplitude- and frequency-response curves were similar to those of depressant responses. Biphasic-2 responses differed in that the response was biphasic when the stimulation frequency was 80 Hz or greater and the amplitude was 0.3 mm or more, yet, at lower frequencies and/or amplitudes vibration evoked excitation. The similarities in the amplitude- and frequency-response relationships of depressant and biphasic-1 responses raise the possibility that these responses might be mediated by a single class of primary afferent. Both depressant and biphasic responses were evoked when stimulation parameters (2 microns, 240 Hz) were used which selectively activate Pacinian corpuscle afferents. Depression with 240-Hz stimulation was attenuated by administration of caffeine (60 mg/kg i.v.) suggesting that the depressant and biphasic-1 responses may be mediated by afferents from Pacinian corpuscles.
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Affiliation(s)
- M W Salter
- Department of Physiology, McGill University, Montréal, Qué., Canada
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Cervero F, Plenderleith MB. Dorsal root potentials are unchanged in adult rats treated at birth with capsaicin. J Physiol 1984; 357:357-68. [PMID: 6512694 PMCID: PMC1193262 DOI: 10.1113/jphysiol.1984.sp015504] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The possible contribution of non-myelinated afferent fibres (C fibres) to the mechanisms of primary afferent depolarization (p.a.d.) in the spinal cord of the rat has been investigated. Dorsal root potentials (d.r.p.s.) were recorded in the lumbar cord of normal adult rats, of adult rats which had been injected at birth with a solution of capsaicin (50 mgkg-1 s.c.) and of adult rats which had been injected at birth with the drug vehicle only. D.r.p.s were recorded from the dorsal rootlet that entered the spinal cord in the main area of termination of the tibial nerve. The location of this area was assessed by mapping the spinal cord in the rostro-caudal axis while recording cord dorsum potentials evoked by A-fibre volleys from the tibial nerve. No differences in peak amplitude, area or time to peak amplitude were observed between the d.r.p.s evoked in control and capsaicin-treated rats by stimulation of the tibial, sural or common peroneal nerves. The relation between the size of incoming A volleys to the spinal cord and the size of the d.r.p.s evoked by them was unaffected by the neonatal capsaicin treatment. Rats treated at birth with capsaicin showed a virtual absence of afferent C fibres as assessed from the lack of C waves in the compound action potentials evoked in each of the three nerves studied after antidromic stimulation of the dorsal roots. The presence of p.a.d. in control and in capsaicin-treated animals was also established using the technique of excitability testing of primary afferent fibres (Wall, 1958). No differences were observed between the p.a.d. recorded in control and in capsaicin-treated animals using this technique. D.r.p.s and p.a.d. (assessed by excitability testing of primary afferent fibres) were of similar magnitude in control and in capsaicin-treated rats anaesthetized with either sodium pentobarbitone or urethane. It is concluded that p.a.d. of myelinated afferent fibres produced by incoming volleys in myelinated afferent fibres is not affected by a life-long loss of non-myelinated afferent fibres.
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Horch KW, Lisney SJ. Changes in primary afferent depolarization of sensory neurones during peripheral nerve regeneration in the cat. J Physiol 1981; 313:287-99. [PMID: 7277220 PMCID: PMC1274451 DOI: 10.1113/jphysiol.1981.sp013665] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
1. Micro-electrode recordings were made from normal and regenerating sural nerve fibres in cats. Increases in the excitability of the central terminals of these fibres after conditioning stimulation of other sural nerve fibres were taken as evidence for primary afferent depolarization. 2. At all recovery times studied the excitability changes seen were significantly less than those seen in control animals. Two factors contributed to the changes in primary afferent depolarization. First, the proportion of fibres that showed no evidence of primary afferent depolarization increased significantly. This proportion became smaller as recovery progressed. Secondly, where primary afferent depolarization was present, the magnitudes of the effects were slightly but significantly decreased compared with control values. 3. Excitability changes of the central terminals of sural nerve fibres were also measured after conditioning stimulation of the ipsilateral, unlesioned accessory sural nerve. One month after sural nerve transection there was a significant increase in the proportion of fibres showing no evidence of excitability changes following accessory sural nerve conditioning stimulation compared with control animals. Thus, the loss of primary afferent depolarization of regenerating sural nerve fibres was neither simply a consequence of desynchronization of the volley of impulses entering the spinal cord after conditioning stimulation of other regenerating sural fibres, nor due to fewer fibres being activated during conditioning stimulation of the lesioned nerves. 4. A possible explanation of these results is that after peripheral nerve crush or transection the central terminals of the damaged fibres retract or atrophy. Then as regeneration of the nerve proceeds, the central terminals of the fibres re-form.
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Barber RP, Vaughn JE, Saito K, McLaughlin BJ, Roberts E. GABAergic terminals are presynaptic to primary afferent terminals in the substantia gelatinosa of the rat spinal cord. Brain Res 1978; 141:35-55. [PMID: 624076 DOI: 10.1016/0006-8993(78)90615-7] [Citation(s) in RCA: 293] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Bystrzycka E, NAil BS, Rowe M. Inhibition of cuneate neurones: its afferent source and influence on dynamically sensitive "tactile" neurones. J Physiol 1977; 268:251-70. [PMID: 874897 PMCID: PMC1283662 DOI: 10.1113/jphysiol.1977.sp011856] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
1. Responses were recorded in decereberate, unanaesthetized cats from individual cuneate neurones in order to determine firstly, the afferent sources of inhibition on cuneate neurones and secondly, the influence of afferent-induced inhibition on those response features of dynamically sensitive tactile neurones which determine their capacity to code information about parameters of tactile stimuli.2. For all cuneate neurones which displayed afferent-induced inhibition from areas surrounding or within their excitatory receptive field (71% of the sample) it was consistently found that 300 Hz vibration at low amplitudes (< 25-50 mum) which selectively engages Pacinian corpuscles was an effective source of inhibition. In contrast, steady indentation which activates slowly adapting tactile afferents was quite ineffective, as was low frequency vibration (30 Hz) at amplitudes of < 50-100 mum. The latter stimulus can be used to engage rapidly adapting receptors either within glabrous skin (presumed to be Meissners corpuscles) or in association with hair follicles. It is concluded that afferents from Pacinian corpuscles are the dominant or exclusive source of afferent-induced inhibition of cuneate neurones.3. For dynamically sensitive neurones responsive to low frequency cutaneous vibration (30 Hz) there was a reduction in the slope of stimulus-response relations with afferent-induced inhibition, but no expansion of the range of stimulus amplitudes over which the neurone responded.4. The influence of afferent-induced inhibition on the phase-locking of impulse activity to a cutaneous vibratory wave form was examined by constructing post-stimulus time histograms and cycle histograms. Measures of dispersion of impulse activity around the preferred point of firing in the vibratory waveform indicated that the capacity of individual cuneate neurones to code information about the frequency of the cutaneous vibration was not systematically changed in the presence of afferent-induced inhibition.
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Carmody J, Rowe M. Inhibition within the trigeminal nucleus induced by afferent inputs and its influence on stimulus coding by mechanosensitive neurones. J Physiol 1974; 243:195-210. [PMID: 4449060 PMCID: PMC1330696 DOI: 10.1113/jphysiol.1974.sp010749] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
1. In decerebrate, unanaesthetized cats two thirds of slowly adapting mechanosensitive neurones sampled in the trigeminal nucleus oralis exhibited inhibition in response to conditioning mechanical stimulation applied beyond their excitatory receptive fields. The influence of this inhibition was examined over the response range of these neurones using controlled, reproducible natural stimulation procedures.2. The extent of the inhibition was graded according to the intensity of the conditioning stimulus. It was evoked most strongly by vibratory skin indentation which very effectively excites rapidly adapting afferent fibres. Tonic conditioning inputs associated with steady skin indentation were less effective.3. The slope of stimulus-response relationships constructed from responses to inputs from the excitatory receptive field was reduced in 42% of trigeminal nuclear cells in the presence of afferent-induced inhibition. In the remainder the slope was unchanged.4. There was no evidence, in the neurones subject to inhibition, of an expansion of their dynamic range defined as the range of stimulus intensities over which a neurone exhibited a graded responsiveness.5. The variability in responses of an individual neurone at a given stimulus intensity was unchanged by this inhibition.6. Analysis of the stimulus-response data using information theory statistics revealed that neurones which underwent a reduction in the slope of their stimulus-response relationship in the presence of inhibition displayed a reduced capacity for defining the intensity of skin indentation. This capacity was not modified in those neurones where the slope was unchanged by the peripherally evoked inhibition.
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Putnam JE, Whitehorn D. Polarization changes in the terminals of identified primary afferent fibers at the gracile nucleus. Exp Neurol 1973; 41:246-59. [PMID: 4355645 DOI: 10.1016/0014-4886(73)90266-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Gregor M, Zimmermann M. Dorsal root potentials produced by afferent volleys in cutaneous group 3 fibers. J Physiol 1973; 232:413-25. [PMID: 4759676 PMCID: PMC1350501 DOI: 10.1113/jphysiol.1973.sp010278] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
1. Dorsal root potentials (DRP) were recorded in the lumbosacral spinal cord of decerebrated unanaesthetized cats, following afferent volleys restricted to the thin myelinated (Group III) cutaneous afferents of the hind limb. The thick myelinated fibres (Group II) were blocked by a depolarizing current.2. A pure Group III volley produced a DRP of negative polarity, called the III-DRP, signalling a depolarization of the intraspinal terminals of afferent fibres. The longer latency of the III-DRP when compared to that of the DRP after a Group II volley was accounted for quantitatively by the lower conduction velocity of the Group III fibres.3. Special attention was given to the presence of III-DRPs having a predominantly positive polarity thus signalling a presynaptic hyperpolarization. Such ;positive III-DRPs' were, however, never observed in this investigation.4. Both after transection of the spinal cord at various levels and after administration of pentobarbitone the III-DRP persisted at normal polarity. The duration of the DRPs was increased by these experimental procedures.5. The implications of these findings are discussed in relation to the prominent role postulated for the Group III fibres in the context of the gate control theory of pain.
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Young RF, King RB. Excitability changes in trigeminal primary afferent fibres elicited by dental pulp stimulation in the cat. Arch Oral Biol 1972; 17:1649-57. [PMID: 4509575 DOI: 10.1016/0003-9969(72)90227-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Andersen P, Etholm B, Gordon G. Presynaptic and post-synaptic inhibition elicited in the cat's dorsal column nuclei by mechanical stimulation of skin. J Physiol 1970; 210:433-55. [PMID: 5501269 PMCID: PMC1395567 DOI: 10.1113/jphysiol.1970.sp009219] [Citation(s) in RCA: 66] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
1. Primary afferent depolarization (PAD), with a time course comparable with that of the PAD following limb nerve stimulation, was produced in the cuneate nucleus by mechanical stimulation of the skin of the ipsilateral forepaw. Brushing or blowing on hairs was as effective as any other form of stimulation and there was a rapid adaptation to a sustained stimulus. Up to 55% increase in excitability was produced by blowing on hairs.2. The P-wave and the PAD produced by mechanical stimulation were at a minimum in the rostral part of the cuneate nucleus and at a maximum 2-6 mm caudal to the obex.3. The distribution of the PAD produced in the gracile nucleus by blowing on the skin of the hind foot was studied by a technique allowing measurement of excitability changes near the terminals of single fibres. Minimal values were obtained rostral to the obex and maximal values 1-4 mm caudal to the obex, a distribution matching that previously determined for single cells subject to surround inhibition.4. Post-synaptic inhibition was produced in the cuneate nucleus by gentle blowing on the ipsilateral forepaw. Up to 20% fall in excitability occurred in populations of cells tested by direct electrical stimulation. IPSPs lasting up to 160 msec were observed in single cells following light mechanical stimulation in the immediate neighbourhood of these cells' receptive fields. Blocking of antidromic invasion of single cells was occasionally produced by mechanical skin stimulation.5. It is concluded that both pre- and post-synaptic inhibition must be concerned in the phenomenon of afferent surround inhibition, though there was no evidence to indicate their relative roles, qualitatively or quantitatively.6. It is shown that up to 20% reduction in transmission through the gracile or cuneate nucleus could be produced by blowing on the ipsilateral hind paw or forepaw respectively, measured as reduction in the area of the monophasically recorded lemniscal response. A single electrical stimulus to the skin of the contralateral forepaw reduced transmission through the cuneate nucleus by less than 5%.
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Fuller DR, Gray JA. A quantitative analysis of the responses of certain dorsal horn neurones to mechanical stimulation of the large foot pad in cats. J Physiol 1969; 200:575-87. [PMID: 5765848 PMCID: PMC1350514 DOI: 10.1113/jphysiol.1969.sp008709] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
1. Responses of single units in the dorsal horns of the spinal cords of cats to mechanical stimulation of the large foot pad have been recorded.2. The observations made with different single stimuli belonging to the set under different conditions of excitability have included: the numbers of impulses per response, their means and variation; the frequency distributions of impulse numbers; the time distribution of activity during a response and in particular the probability of an impulse occurring in each successive time interval.3. The observations with two stimuli were designed to measure the [ill] of the whole response contributed by the second stimulus and [ill] relate the size of this contribution to the interval between the stimuli and their distance apart.4. The results are discussed and it is concluded that the observed transformations allow representations of successive events to exist at the same time and that the purpose of the transformation may therefore be to allow particular types of interaction between successive events. A model of mechanism which is consistent with many of the observations is also discussed.
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Jänig W, Schmidt RF, Zimmermann M. Two specific feedback pathways to the central afferent terminals of phasic and tonic mechanoreceptors. Exp Brain Res 1968; 6:116-29. [PMID: 5721758 DOI: 10.1007/bf00239166] [Citation(s) in RCA: 48] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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23
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Jänig W, Schmidt RF, Zimmermann M. Presynaptic depolarization during activation of tonic mechanoreceptors. Brain Res 1967; 5:514-6. [PMID: 6049967 DOI: 10.1016/0006-8993(67)90024-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Vortr�ge der 33. Tagung (Fr�hjahrstagung) der Deutschen Physiologischen Gesellschaft vom 12. April bis 14. April 1967 in W�rzburg. Pflugers Arch 1967. [DOI: 10.1007/bf00412990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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