scholarly journals Modulation of Spinal GABAergic Inhibition and Mechanical Hypersensitivity following Chronic Compression of Dorsal Root Ganglion in the Rat

2015 ◽  
Vol 2015 ◽  
pp. 1-12
Author(s):  
Moon Chul Lee ◽  
Taick Sang Nam ◽  
Se Jung Jung ◽  
Young S. Gwak ◽  
Joong Woo Leem
Keyword(s):  
Dorsal Root Ganglion ◽  
Early Phase ◽  
Dorsal Root ◽  
Neuronal Excitability ◽  
Late Phase ◽  
Gabaergic Inhibition ◽  
Mechanical Sensitivity ◽  
Gaba A ◽  
Mechanical Hypersensitivity ◽  
Injured Side

Chronic compression of dorsal root ganglion (CCD) results in neuropathic pain. We investigated the role of spinal GABA in CCD-induced pain using rats with unilateral CCD. A stereological analysis revealed that the proportion of GABA-immunoreactive neurons to total neurons at L4/5 laminae I–III on the injured side decreased in the early phase of CCD (post-CCD week 1) and then returned to the sham-control level in the late phase (post-CCD week 18). In the early phase, the rats showed an increase in both mechanical sensitivity of the hind paw and spinal WDR neuronal excitability on the injured side, and such increase was suppressed by spinally applied muscimol (GABA-A agonist, 5 nmol) and baclofen (GABA-B agonist, 25 nmol), indicating the reduced spinal GABAergic inhibition involved. In the late phase, the CCD-induced increase in mechanical sensitivity and neuronal excitability returned to pre-CCD levels, and such recovered responses were enhanced by spinally applied bicuculline (GABA-A antagonist, 15 nmol) and CGP52432 (GABA-B antagonist, 15 nmol), indicating the regained spinal GABAergic inhibition involved. In conclusion, the alteration of spinal GABAergic inhibition following CCD and leading to a gradual reduction over time of CCD-induced mechanical hypersensitivity is most likely due to changes in GABA content in spinal GABA neurons.

Molecular Changes in the Dorsal Root Ganglion during the Late Phase of Peripheral Nerve Injury–induced Pain in Rodents: A Systematic Review

2021 ◽  
Author(s):  
Mehrman Chalaki ◽  
Luis J. Cruz ◽  
Sabien G. A. van Neerven ◽  
Joost Verhaagen ◽  
Albert Dahan ◽  
...  
Keyword(s):  
Dorsal Root Ganglion ◽  
Messenger Rna ◽  
Dorsal Root ◽  
Current Knowledge ◽  
Late Phase ◽  
Molecular Changes ◽  
Genomic Changes ◽  
Protein Levels ◽  
Fundamental Understanding ◽  
Sequencing Studies

The dorsal root ganglion is widely recognized as a potential target to treat chronic pain. A fundamental understanding of quantitative molecular and genomic changes during the late phase of pain is therefore indispensable. The authors performed a systematic literature review on injury-induced pain in rodent dorsal root ganglions at minimally 3 weeks after injury. So far, slightly more than 300 molecules were quantified on the protein or messenger RNA level, of which about 60 were in more than one study. Only nine individual sequencing studies were performed in which the most up- or downregulated genes varied due to heterogeneity in study design. Neuropeptide Y and galanin were found to be consistently upregulated on both the gene and protein levels. The current knowledge regarding molecular changes in the dorsal root ganglion during the late phase of pain is limited. General conclusions are difficult to draw, making it hard to select specific molecules as a focus for treatment.

Reduction in Potassium Currents in Identified Cutaneous Afferent Dorsal Root Ganglion Neurons After Axotomy

1999 ◽  
Vol 82 (2) ◽  
pp. 700-708 ◽  
Author(s):  
Brian Everill ◽  
Jeffery D. Kocsis
Keyword(s):  
Dorsal Root Ganglion ◽  
Dorsal Root ◽  
Neuronal Excitability ◽  
Potassium Currents ◽  
Dorsal Root Ganglion Neurons ◽  
Channel Blockers ◽  
Afferent Neurons ◽  
Drg Neurons ◽  
Whole Cell Patch Clamp ◽  
Ganglion Neurons

Potassium currents have an important role in modulating neuronal excitability. We have investigated the effects of axotomy on three voltage-activated K+ currents, one sustained and two transient, in cutaneous afferent dorsal root ganglion (DRG) neurons. Fourteen to 21 days after axotomy, L4 and L5 DRG neurons were acutely dissociated and were studied 2–8 h after plating. Whole cell patch-clamp recordings were obtained from identified cutaneous afferent neurons (46–50 μm diam); K+ currents were isolated by blocking Na+ and Ca2+ currents with appropriate ion replacement and channel blockers. Separation of the current components was achieved on the basis of sensitivity to dendrotoxin or 4-aminopyridine and by the response to variation in conditioning voltage. Both control and injured neurons displayed qualitatively similar complex K+ currents composed of distinct kinetic and pharmacological components. Three distinct K+ current components, a sustained ( I K) and two transient ( I A and I D), were identified in variable proportions. However, total peak current was reduced by 52% in the axotomized cells when compared with control cells. Two current components were reduced after ligation, I Aby 60%, I K by over 65%, compared with control cells. I D appeared unaffected after acute ligation. These results indicate a large reduction in overall K+ current, resulting from reductions in I K and I A, on large cutaneous afferent neurons after nerve ligation and have implications for excitability changes of injured primary afferent neurons.

GDNF and NGF Reverse Changes in Repriming of TTX-Sensitive Na+ Currents Following Axotomy of Dorsal Root Ganglion Neurons

2002 ◽  
Vol 88 (2) ◽  
pp. 650-658 ◽  
Author(s):  
Andreas Leffler ◽  
Theodore R. Cummins ◽  
Sulayman D. Dib-Hajj ◽  
William N. Hormuzdiar ◽  
Joel A. Black ◽  
...  
Keyword(s):  
Dorsal Root Ganglion ◽  
Sodium Channel ◽  
Sensory Neurons ◽  
Dorsal Root ◽  
Neuronal Excitability ◽  
Dorsal Root Ganglion Neurons ◽  
Current Profile ◽  
Drg Neurons ◽  
Α Subunit ◽  
Ganglion Neurons

Uninjured C-type rat dorsal root ganglion (DRG) neurons predominantly express slowly inactivating TTX-resistant (TTX-R) and slowly repriming TTX-sensitive (TTX-S) Na+ currents. After peripheral axotomy, TTX-R current density is reduced and rapidly repriming TTX-S currents emerge and predominate. The change in TTX-S repriming kinetics is paralleled by an increase in the level of transcripts and protein for the Nav1.3 sodium channel α-subunit, which is known to exhibit rapid repriming. Changes in Na+current profile and kinetics in DRG neurons may substantially alter neuronal excitability and could contribute to some states of chronic pain associated with injury of sensory neurons. In the present study, we asked whether glial-derived neurotrophic factor (GDNF) and nerve growth factor (NGF), which have been shown to prevent some axotomy-induced changes such as the loss of TTX-R Na+ current expression in DRG neurons, can ameliorate the axotomy-induced change in TTX-S Na+ current repriming kinetics. We show that intrathecally administered GDNF and NGF, delivered individually, can partially reverse the effect of axotomy on the repriming kinetics of TTX-S Na+ currents. When GDNF and NGF were co-administered, the repriming kinetics were fully rescued. We observed parallel effects of GDNF and NGF on the Nav1.3 sodium channel transcript levels in axotomized DRG. Both GDNF and NGF were able to partially reverse the axotomy-induced increase in Nav1.3 mRNA, with GDNF plus NGF producing the largest effect. Our data indicate that both GDNF and NGF can partially reverse an important effect of axotomy on the electrogenic properties of sensory neurons and that their effect is additive.

scholarly journals Biphasic Activation of Extracellular Signal-regulated Kinase in Anterior Cingulate Cortex Distinctly Regulates the Development of Pain-related Anxiety and Mechanical Hypersensitivity in Rats after Incision

2011 ◽  
Vol 115 (3) ◽  
pp. 604-613 ◽  
Author(s):  
Ru-Ping Dai ◽  
Chang-Qi Li ◽  
Jian-Wei Zhang ◽  
Fang Li ◽  
Xu-Dan Shi ◽  
...  
Keyword(s):  
Postoperative Pain ◽  
Anterior Cingulate Cortex ◽  
Early Phase ◽  
Late Phase ◽  
Cingulate Cortex ◽  
Anterior Cingulate ◽  
Erk Activation ◽  
Mechanical Hypersensitivity ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal

Background A recent study has demonstrated that surgical incision induces an anxiety-like behavior but its relationship with incision-evoked mechanical hypersensitivity remains elusive. Extracellular signal-regulated kinase (ERK) activity in the anterior cingulate cortex (ACC) is important for the affective pain. The current study aims to explore ERK1/2 activity in the ACC and its role in the development of anxiety and mechanical hypersensitivity after incision. Methods Anxiety-like behavior was measured by elevated plus maze experiment and open field test after hind paw incision. ERK1/2 phosphorylation was determined by immunohistochemistry and Western blot. Cannulae were implanted into the bilateral ACC for the intra-ACC injection of ERK inhibitors PD98059 and U0126. Brushing (innocuous stimulus) was used to investigate its effect on ERK activation under the incision-evoked painful condition. Results The anxiety-like behavior induced by the hind paw incision persisted longer than mechanical hypersensitivity. One hind paw incision resulted in a biphasic ERK activation in bilateral ACC. Inhibiting ERK activation in the early phase attenuated pain-related anxiety and mechanical hypersensitivity whereas inhibiting ERK activation in the late phase only reduced the anxiety-like behavior. During the time interval between two phases of ERK activation, brushing the incised skin dramatically increased ERK phosphorylation in the ACC. Conclusions These data suggest that in the early phase of postoperative pain, pain-related anxiety and mechanical hypersensitivity are tightly linked and regulated by the ERK activation in the ACC. However, in the late phase of postoperative pain, ERK activation in the ACC is only required for the expression of pain-related anxiety but not mechanical hypersensitivity.

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