1
|
Fan W, Sullivan SJ, Sdrulla AD. Dorsal Column and Root Stimulation at Aβ-fiber Intensity Activate Superficial Dorsal Horn Glutamatergic and GABAergic Populations. Mol Pain 2022; 18:17448069221079559. [PMID: 35088625 PMCID: PMC8891844 DOI: 10.1177/17448069221079559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Neurostimulation therapies are frequently used in patients with chronic pain conditions. They emerged from Gate Control Theory (GCT), which posits that Aβ-fiber activation recruits superficial dorsal horn (SDH) inhibitory networks to “close the gate” on nociceptive transmission, resulting in pain relief. However, the efficacy of current therapies is limited, and the underlying circuits remain poorly understood. For example, it remains unknown whether ongoing stimulation of Aβ-fibers is sufficient to drive activity in SDH neurons. We used multiphoton microscopy in spinal cords extracted from mice expressing the genetically encoded calcium indicator GCaMP6s in glutamatergic and GABAergic populations; activity levels were inferred from deconvolved calcium signals using CaImAn software. Sustained Aβ-fiber stimulation at the dorsal columns or dorsal roots drove robust yet transient activation of both SDH populations. Following the initial increase, activity levels decreased below baseline in glutamatergic neurons and were depressed after stimulation ceased in both populations. Surprisingly, only about half of GABAergic neurons responded to Aβ-fiber stimulation. This subset showed elevated activity for the entire duration of stimulation, while non-responders decreased with time. Our findings suggest that Aβ-fiber stimulation initially recruits both excitatory and inhibitory populations but has divergent effects on their activity, providing a foundation for understanding the analgesic effects of neurostimulation devices. Perspective: This article used microscopy to characterize the responses of mouse spinal cord cells to stimulation of non-painful nerve fibers. These findings deepen our understanding of how the spinal cord processes information and provide a foundation for improving pain-relieving therapies.
Collapse
Affiliation(s)
- Wei Fan
- Anesthesiology and Pain Management6684Oregon Health & Science University
| | - Steve J Sullivan
- Anesthesiology and Pain Management6684Oregon Health & Science University
| | - Andrei D Sdrulla
- Anesthesiology and Pain Management6684Oregon Health & Science University
| |
Collapse
|
2
|
Fan W, Sdrulla AD. Differential modulation of excitatory and inhibitory populations of superficial dorsal horn neurons in lumbar spinal cord by Aβ-fiber electrical stimulation. Pain 2021; 161:1650-1660. [PMID: 32068665 DOI: 10.1097/j.pain.0000000000001836] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Activation of Aβ-fibers is fundamental to numerous analgesic therapies, yet its effects on dorsal horn neuronal activity remain unclear. We used multiphoton microscopy of the genetically encoded calcium indicator GCaMP6s to characterize the effects of Aβ-fiber electrical stimulation (Aβ-ES) on neural activity. Specifically, we quantified somatic responses evoked by C-fiber intensity stimulation before and after a 10-minute train of dorsal root Aβ-ES in superficial dorsal horn (SDH) neurons, in mouse lumbar spinal cord. Aβ-ES did not alter C-fiber-evoked activity when GCaMP6s was virally expressed in all neurons, in an intact lumbar spinal cord preparation. However, when we restricted the expression of GCaMP6s to excitatory or inhibitory populations, we observed that Aβ-ES modestly potentiated evoked activity of excitatory neurons and depressed that of inhibitory neurons. Aβ-ES had no significant effects in a slice preparation in either SDH population. A larger proportion of SDH neurons was activated by Aβ-ES when delivered at a root rostral or caudal to the segment where the imaging and C-fiber intensity stimulation occurred. Aβ-ES effects on excitatory and inhibitory populations depended on the root used. Our findings suggest that Aβ-ES differentially modulates lumbar spinal cord SDH populations in a cell type- and input-specific manner. Furthermore, they underscore the importance of the Aβ-ES delivery site, suggesting that Aβ stimulation at a segment adjacent to where the pain is may improve analgesic efficacy.
Collapse
Affiliation(s)
- Wei Fan
- Department of Anesthesiology and Perioperative Medicine, Oregon Health & Science University, Portland, OR, United States
| | | |
Collapse
|
3
|
Shi Z, Pelletier NE, Wong J, Li B, Sdrulla AD, Madden CJ, Marks DL, Brooks VL. Leptin increases sympathetic nerve activity via induction of its own receptor in the paraventricular nucleus. eLife 2020; 9:e55357. [PMID: 32538782 PMCID: PMC7316512 DOI: 10.7554/elife.55357] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Accepted: 06/12/2020] [Indexed: 12/11/2022] Open
Abstract
Whether leptin acts in the paraventricular nucleus (PVN) to increase sympathetic nerve activity (SNA) is unclear, since PVN leptin receptors (LepR) are sparse. We show in rats that PVN leptin slowly increases SNA to muscle and brown adipose tissue, because it induces the expression of its own receptor and synergizes with local glutamatergic neurons. PVN LepR are not expressed in astroglia and rarely in microglia; instead, glutamatergic neurons express LepR, some of which project to a key presympathetic hub, the rostral ventrolateral medulla (RVLM). In PVN slices from mice expressing GCaMP6, leptin excites glutamatergic neurons. LepR are expressed mainly in thyrotropin-releasing hormone (TRH) neurons, some of which project to the RVLM. Injections of TRH into the RVLM and dorsomedial hypothalamus increase SNA, highlighting these nuclei as likely targets. We suggest that this neuropathway becomes important in obesity, in which elevated leptin maintains the hypothalamic pituitary thyroid axis, despite leptin resistance.
Collapse
Affiliation(s)
- Zhigang Shi
- Department of Physiology and PharmacologyPortlandUnited States
| | | | - Jennifer Wong
- Department of Physiology and PharmacologyPortlandUnited States
| | - Baoxin Li
- Department of Physiology and PharmacologyPortlandUnited States
| | - Andrei D Sdrulla
- Department of Anesthesiology and Perioperative MedicinePortlandUnited States
| | | | - Daniel L Marks
- Department of Pediatrics, Pape Family Pediatric Research Institute, Brenden-Colson Center for Pancreatic Care Oregon Health & Science UniversityPortlandUnited States
| | | |
Collapse
|
4
|
Abstract
Spinal cord stimulation (SCS) is a minimally invasive therapy used for the treatment of chronic neuropathic pain. SCS is a safe and effective alternative to medications such as opioids, and multiple randomized controlled studies have demonstrated efficacy for difficult-to-treat neuropathic conditions such as failed back surgery syndrome. Conventional SCS is believed mediate pain relief via activation of dorsal column Aβ fibers, resulting in variable effects on sensory and pain thresholds, and measurable alterations in higher order cortical processing. Although potentiation of inhibition, as suggested by Wall and Melzack's gate control theory, continues to be the leading explanatory model, other segmental and supraspinal mechanisms have been described. Novel, non-standard, stimulation waveforms such as high-frequency and burst have been shown in some studies to be clinically superior to conventional SCS, however their mechanisms of action remain to be determined. Additional studies are needed, both mechanistic and clinical, to better understand optimal stimulation strategies for different neuropathic conditions, improve patient selection and optimize efficacy.
Collapse
Affiliation(s)
- Andrei D Sdrulla
- Department of Anesthesiology and Perioperative Medicine, Oregon Health & Science University, Portland, Oregon, U.S.A
| | - Yun Guan
- Department of Anesthesiology and Critical Care Medicine, School of Medicine, Johns Hopkins University, Baltimore, Maryland, U.S.A.,Department of Neurological Surgery, School of Medicine, Johns Hopkins University, Baltimore, Maryland, U.S.A
| | - Srinivasa N Raja
- Department of Anesthesiology and Critical Care Medicine, School of Medicine, Johns Hopkins University, Baltimore, Maryland, U.S.A
| |
Collapse
|
5
|
Sdrulla AD, Xu Q, He SQ, Tiwari V, Yang F, Zhang C, Shu B, Shechter R, Raja SN, Wang Y, Dong X, Guan Y. Electrical stimulation of low-threshold afferent fibers induces a prolonged synaptic depression in lamina II dorsal horn neurons to high-threshold afferent inputs in mice. Pain 2015; 156:1008-1017. [PMID: 25974163 PMCID: PMC4437220 DOI: 10.1097/01.j.pain.0000460353.15460.a3] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Electrical stimulation of low-threshold Aβ-fibers (Aβ-ES) is used clinically to treat neuropathic pain conditions that are refractory to pharmacotherapy. However, it is unclear how Aβ-ES modulates synaptic responses to high-threshold afferent inputs (C-, Aδ-fibers) in superficial dorsal horn. Substantia gelatinosa (SG) (lamina II) neurons are important for relaying and modulating converging spinal nociceptive inputs. We recorded C-fiber-evoked excitatory postsynaptic currents (eEPSCs) in spinal cord slices in response to paired-pulse test stimulation (500 μA, 0.1 millisecond, 400 milliseconds apart). We showed that 50-Hz and 1000-Hz, but not 4-Hz, Aβ-ES (10 μA, 0.1 millisecond, 5 minutes) induced prolonged inhibition of C-fiber eEPSCs in SG neurons in naive mice. Furthermore, 50-Hz Aβ-ES inhibited both monosynaptic and polysynaptic forms of C-fiber eEPSC in naive mice and mice that had undergone spinal nerve ligation (SNL). The paired-pulse ratio (amplitude second eEPSC/first eEPSC) increased only in naive mice after 50-Hz Aβ-ES, suggesting that Aβ-ES may inhibit SG neurons by different mechanisms under naive and nerve-injured conditions. Finally, 50-Hz Aβ-ES inhibited both glutamatergic excitatory and GABAergic inhibitory interneurons, which were identified by fluorescence in vGlut2-Td and glutamic acid decarboxylase-green fluorescent protein transgenic mice after SNL. These findings show that activities in Aβ-fibers lead to frequency-dependent depression of synaptic transmission in SG neurons in response to peripheral noxious inputs. However, 50-Hz Aβ-ES failed to induce cell-type-selective inhibition in SG neurons. The physiologic implication of this novel form of synaptic depression for pain modulation by Aβ-ES warrants further investigation.
Collapse
Affiliation(s)
- Andrei D. Sdrulla
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Qian Xu
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
- Howard Hughes Medical Institute, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Shao-Qiu He
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Vinod Tiwari
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Fei Yang
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Chen Zhang
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
- Department of Anesthesiology, Beijing Chaoyang Hospital, Capital Medical University, Beijing 100020, China
| | - Bin Shu
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Ronen Shechter
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Srinivasa N. Raja
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Yun Wang
- Department of Anesthesiology, Beijing Chaoyang Hospital, Capital Medical University, Beijing 100020, China
| | - Xinzhong Dong
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
- Howard Hughes Medical Institute, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Yun Guan
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| |
Collapse
|
6
|
Sdrulla AD, Chen G. The Multidisciplinary Approach to the Management of Substance Abuse. Subst Abus 2015. [DOI: 10.1007/978-1-4939-1951-2_16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
|
7
|
Sdrulla AD, Linden DJ. Double dissociation between long-term depression and dendritic spine morphology in cerebellar Purkinje cells. Nat Neurosci 2007; 10:546-8. [PMID: 17435753 DOI: 10.1038/nn1889] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2007] [Accepted: 03/09/2007] [Indexed: 11/08/2022]
Abstract
Experiments in hippocampal area CA1 suggest that long-term potentiation could be associated with spine addition and enlargement, and long-term depression (LTD) with spine shrinkage and loss. Is this a general principle of synaptic plasticity? We used two-photon microscopy to measure dendritic spines in rat cerebellar Purkinje cells. Neither local synaptic induction of LTD nor global chemical induction of LTD changed spine number or size. Conversely, a manipulation that evoked persistent dendritic spine retraction did not alter parallel fiber-evoked excitatory postsynaptic currents.
Collapse
Affiliation(s)
- Andrei D Sdrulla
- Department of Neuroscience, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, 916 Hunterian Building, Baltimore, Maryland 21205, USA
| | | |
Collapse
|
8
|
Sdrulla AD, Linden DJ. Dynamic imaging of cerebellar Purkinje cells reveals a population of filopodia which cross-link dendrites during early postnatal development. Cerebellum 2006; 5:105-15. [PMID: 16818385 DOI: 10.1080/14734220600620908] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Two-photon microscopy was used to image dye-loaded filopodia of Purkinje cells in acute rat cerebellar slices. In the process of examining filopodia in Purkinje cells from a period of rapid dendritic growth (P10-21), we observed a small subset of filopodia which appeared to form connections between two dendrites of the same cell, usually between the tips of two adjacent dendrites or the tip of a dendrite and the shaft of another. There were fewer of these 'filopodial bridges' present at P18-21 than at an earlier stage in development (P10-12) and they were absent in mature Purkinje cells. Filopodial bridges do not appear to be an artifact of living brain slice preparation as they may also be seen by dye-loading Purkinje cells in slices prepared from perfusion-fixed brain. They have varied morphologies which are mostly similar to conventional, unattached filopodia. However, when measured over tens of minutes, filopodial bridges were observed to be less motile than conventional filopodia as indicated by a reduced index of expansion. While the functions of these novel structures are unknown it is attractive to speculate that they play an instructive role in Purkinje cell dendritic development.
Collapse
Affiliation(s)
- Andrei D Sdrulla
- Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | | |
Collapse
|
9
|
Abstract
In this study, we show that oligodendrocyte differentiation is powerfully inhibited by activation of the Notch pathway. Oligodendrocytes and their precursors in the developing rat optic nerve express Notch1 receptors and, at the same time, retinal ganglion cells express Jagged1, a ligand of the Notch1 receptor, along their axons. Jagged1 expression is developmentally regulated, decreasing with a time course that parallels myelination in the optic nerve. These results suggest that the timing of oligodendrocyte differentiation and myelination is controlled by the Notch pathway and raise the question of whether localization of myelination is controlled by this pathway.
Collapse
Affiliation(s)
- S Wang
- Stanford University School of Medicine, Department of Neurobiology, California 94305, USA
| | | | | | | | | | | | | | | |
Collapse
|