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de Kort AR, Joosten EAJ, Patijn J, Tibboel D, van den Hoogen NJ. The development of descending serotonergic modulation of the spinal nociceptive network: a life span perspective. Pediatr Res 2022; 91:1361-1369. [PMID: 34257402 DOI: 10.1038/s41390-021-01638-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 06/10/2021] [Accepted: 06/16/2021] [Indexed: 02/06/2023]
Abstract
The nociceptive network, responsible for transmission of nociceptive signals that generate the pain experience, is not fully developed at birth. Descending serotonergic modulation of spinal nociception, an important part of the pain network, undergoes substantial postnatal maturation and is suggested to be involved in the altered pain response observed in human newborns. This review summarizes preclinical data of the development of descending serotonergic modulation of the spinal nociceptive network across the life span, providing a comprehensive background to understand human newborn pain experience and treatment. Sprouting of descending serotonergic axons, originating from the rostroventral medulla, as well as changes in receptor function and expression take place in the first postnatal weeks of rodents, corresponding to human neonates in early infancy. Descending serotonergic modulation switches from facilitation in early life to bimodal control in adulthood, masking an already functional 5-HT inhibitory system at early ages. Specifically the 5-HT3 and 5-HT7 receptors seem distinctly important for pain facilitation at neonatal and early infancy, while the 5-HT1a, 5-HT1b, and 5-HT2 receptors mediate inhibitory effects at all ages. Analgesic therapy that considers the neurodevelopmental phase is likely to result in a more targeted treatment of neonatal pain and may improve both short- and long-term effects. IMPACT: The descending serotonergic system undergoes anatomical changes from birth to early infancy, as its sprouts and descending projections increase and the dorsal horn innervation pattern changes. Descending serotonergic modulation from the rostral ventral medulla switches from facilitation in early life via the 5-HT3 and 5-HT7 receptors to bimodal control in adulthood. A functional inhibitory serotonergic system mainly via 5-HT1a, 5-HT1b, and 5-HT2a receptors at the spinal level exists already at the neonatal phase but is masked by descending facilitation.
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Affiliation(s)
- Anne R de Kort
- Department of Anesthesiology and Pain Management, Maastricht University Medical Centre+, Maastricht, the Netherlands. .,Department of Translational Neuroscience, School of Mental Health and Neuroscience, Maastricht University, Maastricht, the Netherlands.
| | - Elbert A J Joosten
- Department of Anesthesiology and Pain Management, Maastricht University Medical Centre+, Maastricht, the Netherlands.,Department of Translational Neuroscience, School of Mental Health and Neuroscience, Maastricht University, Maastricht, the Netherlands
| | - Jacob Patijn
- Department of Anesthesiology and Pain Management, Maastricht University Medical Centre+, Maastricht, the Netherlands.,Department of Translational Neuroscience, School of Mental Health and Neuroscience, Maastricht University, Maastricht, the Netherlands
| | - Dick Tibboel
- Intensive Care and Department of Pediatric Surgery, Erasmus MC-Sophia Children's Hospital, Rotterdam, the Netherlands
| | - Nynke J van den Hoogen
- Department of Anesthesiology and Pain Management, Maastricht University Medical Centre+, Maastricht, the Netherlands.,Department of Translational Neuroscience, School of Mental Health and Neuroscience, Maastricht University, Maastricht, the Netherlands.,Department of Comparative Biology and Experimental Medicine, Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
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Giniatullin R. 5-hydroxytryptamine in migraine: The puzzling role of ionotropic 5-HT 3 receptor in the context of established therapeutic effect of metabotropic 5-HT 1 subtypes. Br J Pharmacol 2021; 179:400-415. [PMID: 34643938 DOI: 10.1111/bph.15710] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Revised: 09/27/2021] [Accepted: 09/28/2021] [Indexed: 12/16/2022] Open
Abstract
5-hydroxytryptamine (5-HT; serotonin) is traditionally considered as a key mediator implicated in migraine. Multiple 5-HT receptor subtypes contribute to a variety of region-specific functional effects. The raphé nuclei control nociceptive inputs by releasing 5-HT in the brainstem, whereas dural mast cells provide the humoral source of 5-HT in the meninges. Triptans (5-HT1B/D agonists) and ditans (5-HT1F agonists) are the best established 5-HT anti-migraine agents. However, activation of meningeal afferents via ionotropic 5-HT3 receptors results in long-lasting excitatory drive suggesting a pro-nociceptive role for these receptors in migraine. Nevertheless, clinical data do not clearly support the applicability of currently available 5-HT3 antagonists to migraine treatment. The reasons for this might be the presence of 5-HT3 receptors on inhibitory interneurons dampening the excitatory drive, a lack of 5-HT3 A-E subunit-selective antagonists and gender/age-dependent effects. This review is focusing on the controversial role of 5-HT3 receptors in migraine pathology and related pharmacological perspectives of 5-HT ligands.
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Affiliation(s)
- Rashid Giniatullin
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland.,Laboratory of Neurobiology, Kazan Federal University, Kazan, Russia
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Bardoni R. Serotonergic Modulation of Nociceptive Circuits in Spinal Cord Dorsal Horn. Curr Neuropharmacol 2020; 17:1133-1145. [PMID: 31573888 PMCID: PMC7057206 DOI: 10.2174/1570159x17666191001123900] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 08/28/2019] [Accepted: 09/26/2019] [Indexed: 01/12/2023] Open
Abstract
Background: Despite the extensive number of studies performed in the last 50 years, aimed at describing the role of serotonin and its receptors in pain modulation at the spinal cord level, several aspects are still not entirely understood. The interpretation of these results is often complicated by the use of different pain models and animal species, together with the lack of highly selective agonists and antagonists binding to serotonin receptors. Method: In this review, a search has been conducted on studies investigating the modulatory action exerted by serotonin on specific neurons and circuits in the spinal cord dorsal horn. Particular attention has been paid to studies employing electro-physiological techniques, both in vivo and in vitro. Conclusion: The effects of serotonin on pain transmission in dorsal horn depend on several factors, including the type of re-ceptors activated and the populations of neurons involved. Recently, studies performed by activating and/or recording from identified neurons have importantly contributed to the understanding of serotonergic modulation on dorsal horn circuits.
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Affiliation(s)
- Rita Bardoni
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, 41125, Italy
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Ovsepian SV, Vesselkin NP. Serotonergic modulation of synaptic transmission and action potential firing in frog motoneurons. Brain Res 2006; 1102:71-7. [PMID: 16806121 DOI: 10.1016/j.brainres.2006.04.035] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2006] [Revised: 04/10/2006] [Accepted: 04/10/2006] [Indexed: 12/13/2022]
Abstract
Frog spinal neurons receive a prominent innervation from the bulbar serotonergic nuclear complex. We used an isolated spinal cord preparation to examine the effect of serotonin (5-hydroxytryptamine, 5-HT) receptor activation on segmental and descending monosynaptic excitatory inputs to frog lumbar motoneurons. Bath-application of 5-HT (0.05 mM) caused a significant reduction in the peak amplitude of segmental EPSP elicited by dorsal root (DR) stimulation (P < 0.05). Contrasting to DR evoked responses 5-HT did not affect the descending monosynaptic EPSP conditioned by ventrolateral column (VLC) stimulation. Recording of the VLC induced EPSP-spike (E-S) field response within the ventral horn motor nucleus disclosed a substantial enhancement in the population discharge of motoneurons upon 5-HT application (P < 0.05). These data suggest the potential importance of serotonergic receptors in motor integration and gaining of motor output in the frog spinal cord.
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Affiliation(s)
- Saak V Ovsepian
- Department of Neuroscience, School of Medicine, CWRU, Cleveland, OH 44106, USA.
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Shay BL, Hochman S. Serotonin alters multi-segmental convergence patterns in spinal cord deep dorsal horn and intermediate laminae neurons in an in vitro young rat preparation. Pain 2002; 95:7-14. [PMID: 11790462 DOI: 10.1016/s0304-3959(01)00364-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Each spinal neuron has a receptive field that corresponds to stimulation of a specific area of skin or subcutaneous tissue. Receptive fields are plastic and can be altered during development and injury but the actions of neuromodulators, such as serotonin (5-hydroxytryptamine, 5-HT) on receptive field properties are not well known. We used stimulation of multiple adjacent dorsal root spinal segments as a measure of "receptive field size" to determine the effects of 5-HT on multi-segmental convergent input onto neurons in laminae IV-VII. Whole-cell patch-clamp recordings were undertaken in the in vitro hemisected thoracolumbar spinal cord of rats aged 8-10 days old. Based on synaptic responses, neurons could be divided into two predominant groups and 5-HT exerted different effects on these groups. The first group received excitatory post-synaptic potentials (EPSPs) from the homonymous dorsal root but inhibitory post-synaptic potentials (IPSPs) with increasing amplitude from more distant dorsal roots. In this group, 5-HT preferentially depressed the IPSPs from adjacent nerve roots while leaving the EPSP intact. The second group received short-latency EPSPs from all segments stimulated and 5-HT potently depressed all synaptic input. In both populations the depressant actions of 5-HT increased with dose (0.1-10.0 microM). Bicuculline and strychnine did not affect the 5-HT induced short-latency synaptic depression. These results suggest that descending serotonergic systems depress spinal sensory convergence in a graded and differentiated manner. The findings are discussed in relation to the modulation of nociceptive signaling.
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Schmidt BJ, Jordan LM. The role of serotonin in reflex modulation and locomotor rhythm production in the mammalian spinal cord. Brain Res Bull 2000; 53:689-710. [PMID: 11165804 DOI: 10.1016/s0361-9230(00)00402-0] [Citation(s) in RCA: 315] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Over the past 40 years, much has been learned about the role of serotonin in spinal cord reflex modulation and locomotor pattern generation. This review presents an historical overview and current perspective of this literature. The primary focus is on the mammalian nervous system. However, where relevant, major insights provided by lower vertebrate models are presented. Recent studies suggest that serotonin-sensitive locomotor network components are distributed throughout the spinal cord and the supralumbar regions are of particular importance. In addition, different serotonin receptor subtypes appear to have different rostrocaudal distributions within the locomotor network. It is speculated that serotonin may influence pattern generation at the cellular level through modulation of plateau properties, an interplay with N-methyl-D-aspartate receptor actions, and afterhyperpolarization regulation. This review also summarizes the origin and maturation of bulbospinal serotonergic projections, serotonin receptor distribution in the spinal cord, the complex actions of serotonin on segmental neurons and reflex pathways, the potential role of serotonergic systems in promoting spinal cord maturation, and evidence suggesting serotonin may influence functional recovery after spinal cord injury.
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Affiliation(s)
- B J Schmidt
- Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.
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Hedo G, Laird JM, Lopez-Garcia JA. Time-course of spinal sensitization following carrageenan-induced inflammation in the young rat: a comparative electrophysiological and behavioural study in vitro and in vivo. Neuroscience 1999; 92:309-18. [PMID: 10392852 DOI: 10.1016/s0306-4522(98)00734-9] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Inflammation of peripheral tissues evokes spontaneous pain and an increased responsiveness to external stimuli known as hyperalgesia, produced by both peripheral and central changes. The central component is initiated by a sustained afferent barrage produced by sensitized peripheral nociceptors, but it is unclear to which extent ongoing nociceptive input is required to maintain these central changes. Here, we have used an isolated preparation of the spinal cord in vitro obtained from eight- to 12-day-old rats to examine spinal plasticity in the absence of naturally occurring afferent inputs. Spinal reflex responses in preparations obtained from naive rats were compared with those from animals with carrageenan-induced inflammation of one hindpaw of 3 h, 6 h and 20 h duration prior to the extraction of the cord. Measurements of thermal (heat) and mechanical hyperalgesia in awake animals were also made at the same time-points. At 6 h post-carrageenan, there was a significant increase in the wind-up evoked by trains of high-intensity (C-fibre) stimuli, and at 20 h increased responses to both trains and single high-intensity stimuli, and a novel wind-up to low-intensity (Abeta-fibre) trains were observed. In contrast, maximal behavioural hyperalgesia was observed by 3 h post-carrageenan, and thermal hyperalgesia had resolved by 20 h, although mechanical hyperalgesia remained. These results show that the induction of spinal plasticity independent of peripheral input is a progressive process with a slow time-course, since significant hyperreflexia in the isolated spinal preparation appears 6 h after inflammation and develops further within 20 h. We conclude that during the first 3 h following inflammation, hyperalgesia is the result of peripheral sensitization and of central mechanisms that depend on an ongoing peripheral input and thus changes were not observed in the isolated spinal cord.
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Affiliation(s)
- G Hedo
- Department of Physiology, University of Alcalá, Madrid, Spain
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Khasabov SG, Lopez-Garcia JA, Asghar AUR, King AE. Modulation of afferent-evoked neurotransmission by 5-HT3 receptors in young rat dorsal horn neurones in vitro: a putative mechanism of 5-HT3 induced anti-nociception. Br J Pharmacol 1999; 127:843-52. [PMID: 10433490 PMCID: PMC1566080 DOI: 10.1038/sj.bjp.0702592] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
1. The in vitro hemisected spinal cord from young rat was used to investigate the mechanism of serotoninergic modulation of primary afferent-mediated synaptic transmission in the dorsal horn through activation of the 5-HT3 receptor. 2. Dorsal root-evoked excitatory post-synaptic potentials (DR-EPSPs) were recorded intracellularly from dorsal horn neurones. Extracellular recordings of the population primary afferent depolarization (PAD) and the dorsal root-evoked dorsal root reflex (DR-DRR) were made from segmental dorsal roots. 3. 5-Hydroxytryptamine (5-HT) and the selective 5-HT3 receptor agonist 1-(m-chloro-phenyl)-biguanide hydrochloride (m-ChPB) (10 and 50 microM) induced statistically significant reductions of the DR-EPSP amplitude (P<0.001) and duration (P<0.001) in the majority of dorsal horn neurones. The 5-HT3 receptor selective antagonists 3-Tropanyl-indole-3-carboxylate hydrochloride (Tropisetron, 10 microM) and N-(1-Azabicyclo[2.2.2]oct-3-yl)-6-chloro-4-methyl-3-oxo-3,4-dihydro-2H-1 ,4-benzoxazine-8-carboxamide (Y-25130, 10 microM) abolished m-ChPB-induced DR-EPSP attenuation and partially blocked the 5-HT effect. 4. m-ChPB (50 microM)-induced DR-EPSP amplitude and duration attenuation was retained in the presence of the GABA(A) receptor antagonist bicuculline (30 microM), the GABA(B) receptor antagonist saclofen (50 microM) and the opioid receptor antagonist naloxone (50 microM). 5. Both 5-HT and m-ChPB (10 and 50 microM) induced a PAD but the mean peak amplitude of 5-HT-induced PAD was significantly greater than PAD to m-ChPB (98.6+/-12 microV compared to 51.8+/-10 V for 50 microM of agonist, respectively). Tropisetron partially reduced 5-HT-induced PAD and abolished m-ChPB-induced PAD. 5-HT, but not m-ChPB, significantly (P<0.001) reduced the peak amplitude of the DR-DRR and this action of 5-HT was unaffected by Tropisetron or Y-25130. 6. These data provide experimental evidence for a putative cellular mechanism at the level of the dorsal horn for anti-nociceptive effects of 5-HT3 receptor activation. This 5-HT3-mediated modulation of sensory afferent transmission was evidently independent of inhibitory GABA- or opioid-dependent interneuronal pathways. The extent to which the 5-HT3 receptor could be involved in the operation of endogenous analgesia and sensory modulation by descending monoamine bulbo-spinal pathways is discussed.
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Affiliation(s)
- S G Khasabov
- School of Biomedical Sciences, University of Leeds, Leeds, LS2 9NQ, U.K
| | - J A Lopez-Garcia
- School of Biomedical Sciences, University of Leeds, Leeds, LS2 9NQ, U.K
- 1-Depto. Fisiologia, Facultad de Medicina, Universidad de Alcala, Madrid 2871, Spain
| | - A U R Asghar
- School of Biomedical Sciences, University of Leeds, Leeds, LS2 9NQ, U.K
| | - A E King
- School of Biomedical Sciences, University of Leeds, Leeds, LS2 9NQ, U.K
- Author for correspondence:
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Abstract
The highly disagreeable sensation of pain results from an extraordinarily complex and interactive series of mechanisms integrated at all levels of the neuroaxis, from the periphery, via the dorsal horn to higher cerebral structures. Pain is usually elicited by the activation of specific nociceptors ('nociceptive pain'). However, it may also result from injury to sensory fibres, or from damage to the CNS itself ('neuropathic pain'). Although acute and subchronic, nociceptive pain fulfils a warning role, chronic and/or severe nociceptive and neuropathic pain is maladaptive. Recent years have seen a progressive unravelling of the neuroanatomical circuits and cellular mechanisms underlying the induction of pain. In addition to familiar inflammatory mediators, such as prostaglandins and bradykinin, potentially-important, pronociceptive roles have been proposed for a variety of 'exotic' species, including protons, ATP, cytokines, neurotrophins (growth factors) and nitric oxide. Further, both in the periphery and in the CNS, non-neuronal glial and immunecompetent cells have been shown to play a modulatory role in the response to inflammation and injury, and in processes modifying nociception. In the dorsal horn of the spinal cord, wherein the primary processing of nociceptive information occurs, N-methyl-D-aspartate receptors are activated by glutamate released from nocisponsive afferent fibres. Their activation plays a key role in the induction of neuronal sensitization, a process underlying prolonged painful states. In addition, upon peripheral nerve injury, a reduction of inhibitory interneurone tone in the dorsal horn exacerbates sensitized states and further enhance nociception. As concerns the transfer of nociceptive information to the brain, several pathways other than the classical spinothalamic tract are of importance: for example, the postsynaptic dorsal column pathway. In discussing the roles of supraspinal structures in pain sensation, differences between its 'discriminative-sensory' and 'affective-cognitive' dimensions should be emphasized. The purpose of the present article is to provide a global account of mechanisms involved in the induction of pain. Particular attention is focused on cellular aspects and on the consequences of peripheral nerve injury. In the first part of the review, neuronal pathways for the transmission of nociceptive information from peripheral nerve terminals to the dorsal horn, and therefrom to higher centres, are outlined. This neuronal framework is then exploited for a consideration of peripheral, spinal and supraspinal mechanisms involved in the induction of pain by stimulation of peripheral nociceptors, by peripheral nerve injury and by damage to the CNS itself. Finally, a hypothesis is forwarded that neurotrophins may play an important role in central, adaptive mechanisms modulating nociception. An improved understanding of the origins of pain should facilitate the development of novel strategies for its more effective treatment.
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Affiliation(s)
- M J Millan
- Institut de Recherches Servier, Psychopharmacology Department, Paris, France
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Khasabov SG, Lopez-Garcia JA, King AE. Serotonin-induced population primary afferent depolarisation in vitro: the effects of neonatal capsaicin treatment. Brain Res 1998; 789:339-42. [PMID: 9573398 DOI: 10.1016/s0006-8993(98)00136-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The effect of 5-hydroxytryptamine (5-HT) on population primary afferent depolarisation (PAD) has been studied using in vitro spinal cord preparations from normal and capsaicin pre-treated (neonatal subcutaneous injection; 75 mg kg-1) rats aged 10-14 days. In preparations from untreated rats, the concentration-response curve for PAD in response to 0.1-100 microM 5-HT was bell-shaped but in the capsaicin pre-treated group, a non-saturating 5-HT-induced PAD concentration-response curve was generated. Quantitatively, the mean PAD responses to 0.1-10 microM 5-HT were of a greater amplitude in the control group compared to the capsaicin pre-treated group (p</=0. 05). For the highest 5-HT concentration of 100 microM, PAD values were significantly greater in the capsaicin pre-treated group (p</=0. 05). These data indicate that control of sensory afferent polarity may involve two 5-HT receptor types and that nociceptive and non-nociceptive afferents may be targets for released 5-HT.
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Affiliation(s)
- S G Khasabov
- Dept. of Physiology, University of Leeds, Leeds LS2 9NQ, UK
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Lopez-Garcia JA, King AE. Pre- and post-synaptic actions of 5-hydroxytryptamine in the rat lumbar dorsal horn in vitro: implications for somatosensory transmission. Eur J Neurosci 1996; 8:2188-97. [PMID: 8921310 DOI: 10.1111/j.1460-9568.1996.tb00740.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Since the relative contribution of pre- versus post-synaptic actions of 5-hydroxytryptamine (5-HT) to modulation of somatosensory processing in the dorsal hom is not known, recordings from primary afferents and dorsal hom neurons from in vitro rat spinal cord were used to address this issue. 5-HT produced a depression of spontaneous dorsal root potentials and a slow primary afferent depolarization (PAD): the PAD versus 5-HT concentration-response curve was bell shaped (maximum at 5 microM; 250 +/- 41.5 microV). In 28/40 dorsal horn neurons, 5-HT elicited a slow depolarization not clearly associated with a specific input resistance change. Excitatory synaptic transmission from primary afferents to dorsal horn neurons was depressed by 5-HT in 40/45 neurons. 5-HT > or = 5 microM significantly (P < or = 0.05) decreased the amplitude, shortened the total duration and half-decay time of the excitatory post-synaptic potential (EPSP). A dominant effect of 5-HT on longer latency EPSP components was evident. There was not direct relationship between the magnitude of PAD and the reduction of the EPSP by 5-HT. 5-Carboxamidotryptamine, an agonist for 5-HT1 receptors, mimicked the depression of neurotransmission in the dorsal horn without producing PAD. A sample of dorsal horn neurons (n = 8) was injected with biocytin and their morphology described. All had somata within laminae III-VI. In five of these neurons 5-HT depressed the EPSP but in one interneuron-like and one unclassed neuron the EPSP was potentiated. These data suggest that whilst depression of synaptic transmission is the predominant effect of 5-HT in the deep dorsal horn, this is not easily related to PAD or cellular actions of 5-HT on dorsal horn neurons.
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