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Frequency-dependent ERK phosphorylation in spinal neurons by electric stimulation of the sciatic nerve and the role in electrophysiological activity.

Fukui T, Dai Y, Iwata K, Kamo H, Yamanaka H, Obata K, Kobayashi K, Wang S, Cui X, Yoshiya S, Noguchi K - Mol Pain (2007)

Bottom Line: We found that high frequency (0.5 Hz and 10 Hz) but not low frequent (0.05 Hz) stimulus-evoked pERK was partially inhibited by MK-801.The extracellular single unit activities were recorded from the laminae I-II and V of the L4-5 dorsal horn, and we found that blockage of the intracellular ERK signal suppressed the wind-up responses in a dose-dependent manner.These observations indicate that ERK activation plays an important role in the induction of the wind-up responses in dorsal horn nociceptive neurons.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Anatomy and Neuroscience, Hyogo College of Medicine, Mukogawa-cho, Nishinomiya, Hyogo, Japan. fukuiii@hyo-med.ac.jp

ABSTRACT
The phosphorylation of extracellular signal-regulated kinase (pERK) in DRG and dorsal horn neurons is induced by the C-fiber electrical stimulation to the peripheral nerve. The present study was designed to investigate the expression and modulation of pERK in the rat dorsal horn neurons produced by repetitive electrical stimulation, and its involvement in the electrophysiological activity of dorsal horn neurons. Electrical stimulation of C-fiber intensity at different frequencies was applied to the sciatic nerve; the stimuli-induced pERK expression and the activity in dorsal horn neurons were studied by immunohistochemistry and extracellular recording, respectively. Electrical stimulation of C-fibers (3 mA) induced pERK expression in dorsal horn neurons in a frequency-dependent manner, indicating that the frequency of electrical stimulation is an important factor which activates the intracellular signal pathway in the spinal cord. To demonstrate the underlying mechanism of this frequency-dependent pERK expression, an NMDA receptor antagonist, MK-801, and a voltage sensitive calcium channel antagonist, nifedipine, were administrated intrathecally before the stimulation. We found that high frequency (0.5 Hz and 10 Hz) but not low frequent (0.05 Hz) stimulus-evoked pERK was partially inhibited by MK-801. Both high and low frequency stimulus-evoked pERK were inhibited by the nifedipine treatment. The extracellular single unit activities were recorded from the laminae I-II and V of the L4-5 dorsal horn, and we found that blockage of the intracellular ERK signal suppressed the wind-up responses in a dose-dependent manner. In contrast, any change in the mechanically evoked responses was not observed following the administration of ERK inhibitor. These observations indicate that ERK activation plays an important role in the induction of the wind-up responses in dorsal horn nociceptive neurons.

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Number of pERK-ir profiles in lamina I-II, III-IV and V-VI of ipsilateral spinal cord after electrical stimulation at the indicated frequencies (n = 4 in each group, *p < 0.01 compared with control, #p < 0.01, compared with 0.05 Hz).
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Figure 2: Number of pERK-ir profiles in lamina I-II, III-IV and V-VI of ipsilateral spinal cord after electrical stimulation at the indicated frequencies (n = 4 in each group, *p < 0.01 compared with control, #p < 0.01, compared with 0.05 Hz).

Mentions: Without any stimulation of the sciatic nerve, a small number of pERK immunoreactive (pERK-ir) profiles was observed only in the spinal lamina I-II posterior cutaneous nerve territory (Fig. 1A). The posterior cutaneous territory is thought to receive projections from the hip skin that was incised upon exposing the sciatic nerve. Thus, we focused on the pERK labeling only in the sciatic nerve territory of the dorsal horn. Electrical stimulation at 0.05 Hz to the sciatic nerve induced a small number of pERK-ir profiles, not only in superficial lamina, but also in deep laminae (Fig. 1B). The higher frequency electrical stimulation (0.5 Hz, 10 Hz,) induced a clear increase in pERK-ir profiles in the superficial laminae compared to the 0.05 Hz stimulus (Fig. 1C, D). To define cell type of the pERK-ir profiles, a double immunofluorescent staining was performed. The 0.5 Hz (3 mA, 2 ms) electrical stimulation-induced pERK expression co-localized with the NeuN positive cells (Fig. 1E–G), indicating ERK was activated mainly in the spinal neurons after the electrical stimulation. The quantification of labeled neurons in Fig. 2 indicated that the number of pERK-ir profiles induced by high frequency stimulation (0.5 Hz and 10 Hz) was significantly higher than that induced by the low frequency stimulation (0.05 Hz). Thus, the increase of pERK expression was dependent with the frequency of the C-fiber electrical stimulation. However, no significant difference was found between the pERK-ir profiles induced by 0.5 Hz and 10 Hz stimulation (Fig. 2).


Frequency-dependent ERK phosphorylation in spinal neurons by electric stimulation of the sciatic nerve and the role in electrophysiological activity.

Fukui T, Dai Y, Iwata K, Kamo H, Yamanaka H, Obata K, Kobayashi K, Wang S, Cui X, Yoshiya S, Noguchi K - Mol Pain (2007)

Number of pERK-ir profiles in lamina I-II, III-IV and V-VI of ipsilateral spinal cord after electrical stimulation at the indicated frequencies (n = 4 in each group, *p < 0.01 compared with control, #p < 0.01, compared with 0.05 Hz).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1941723&req=5

Figure 2: Number of pERK-ir profiles in lamina I-II, III-IV and V-VI of ipsilateral spinal cord after electrical stimulation at the indicated frequencies (n = 4 in each group, *p < 0.01 compared with control, #p < 0.01, compared with 0.05 Hz).
Mentions: Without any stimulation of the sciatic nerve, a small number of pERK immunoreactive (pERK-ir) profiles was observed only in the spinal lamina I-II posterior cutaneous nerve territory (Fig. 1A). The posterior cutaneous territory is thought to receive projections from the hip skin that was incised upon exposing the sciatic nerve. Thus, we focused on the pERK labeling only in the sciatic nerve territory of the dorsal horn. Electrical stimulation at 0.05 Hz to the sciatic nerve induced a small number of pERK-ir profiles, not only in superficial lamina, but also in deep laminae (Fig. 1B). The higher frequency electrical stimulation (0.5 Hz, 10 Hz,) induced a clear increase in pERK-ir profiles in the superficial laminae compared to the 0.05 Hz stimulus (Fig. 1C, D). To define cell type of the pERK-ir profiles, a double immunofluorescent staining was performed. The 0.5 Hz (3 mA, 2 ms) electrical stimulation-induced pERK expression co-localized with the NeuN positive cells (Fig. 1E–G), indicating ERK was activated mainly in the spinal neurons after the electrical stimulation. The quantification of labeled neurons in Fig. 2 indicated that the number of pERK-ir profiles induced by high frequency stimulation (0.5 Hz and 10 Hz) was significantly higher than that induced by the low frequency stimulation (0.05 Hz). Thus, the increase of pERK expression was dependent with the frequency of the C-fiber electrical stimulation. However, no significant difference was found between the pERK-ir profiles induced by 0.5 Hz and 10 Hz stimulation (Fig. 2).

Bottom Line: We found that high frequency (0.5 Hz and 10 Hz) but not low frequent (0.05 Hz) stimulus-evoked pERK was partially inhibited by MK-801.The extracellular single unit activities were recorded from the laminae I-II and V of the L4-5 dorsal horn, and we found that blockage of the intracellular ERK signal suppressed the wind-up responses in a dose-dependent manner.These observations indicate that ERK activation plays an important role in the induction of the wind-up responses in dorsal horn nociceptive neurons.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Anatomy and Neuroscience, Hyogo College of Medicine, Mukogawa-cho, Nishinomiya, Hyogo, Japan. fukuiii@hyo-med.ac.jp

ABSTRACT
The phosphorylation of extracellular signal-regulated kinase (pERK) in DRG and dorsal horn neurons is induced by the C-fiber electrical stimulation to the peripheral nerve. The present study was designed to investigate the expression and modulation of pERK in the rat dorsal horn neurons produced by repetitive electrical stimulation, and its involvement in the electrophysiological activity of dorsal horn neurons. Electrical stimulation of C-fiber intensity at different frequencies was applied to the sciatic nerve; the stimuli-induced pERK expression and the activity in dorsal horn neurons were studied by immunohistochemistry and extracellular recording, respectively. Electrical stimulation of C-fibers (3 mA) induced pERK expression in dorsal horn neurons in a frequency-dependent manner, indicating that the frequency of electrical stimulation is an important factor which activates the intracellular signal pathway in the spinal cord. To demonstrate the underlying mechanism of this frequency-dependent pERK expression, an NMDA receptor antagonist, MK-801, and a voltage sensitive calcium channel antagonist, nifedipine, were administrated intrathecally before the stimulation. We found that high frequency (0.5 Hz and 10 Hz) but not low frequent (0.05 Hz) stimulus-evoked pERK was partially inhibited by MK-801. Both high and low frequency stimulus-evoked pERK were inhibited by the nifedipine treatment. The extracellular single unit activities were recorded from the laminae I-II and V of the L4-5 dorsal horn, and we found that blockage of the intracellular ERK signal suppressed the wind-up responses in a dose-dependent manner. In contrast, any change in the mechanically evoked responses was not observed following the administration of ERK inhibitor. These observations indicate that ERK activation plays an important role in the induction of the wind-up responses in dorsal horn nociceptive neurons.

Show MeSH
Related in: MedlinePlus