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Aging reduced mechanical sensitivity of unmyelinated afferents electrically identified in the rat skin-saphenous nerve preparations in vitro
Abstracts Platelet-activating factor (PAF) is a lipid mediator derived from cell membrane. It is known that PAF is implicated in various pathological conditions in nervous system and intrathecal administration of PAF analog leads to tactile allodynia. In this study, we examined whether PAF and its receptor in the spinal cord are involved in neuropathic pain following peripheral nerve injury. Using spared nerve injury (SNI) model rats, we investigated the expression of PAF synthases (LysoPAFAT, LPCAT1) and PAF receptor (PAFR) mRNAs in spinal cord. RT-PCR and in situ hybridization revealed that SNI increased LysoPAFAT and PAFR mRNAs in spinal microglia but not LPCAT1 mRNA. Continuous intrathecal administration of the PAFR antagonist (W2086) suppressed mechanical allodynia induced by SNI. Our data suggest that the increase of PAF synthesis in spinal microglia plays a role in the neuropathic pain following peripheral nerve injury. doi:10.1016/j.neures.2009.09.1191
P3-d10 Expression and phosphorylation of ERM family proteins in rat spinal dorsal horn with spared nerve injury (SNI) model Ryosuke Kashimoto 1 , Hiroki Yamanaka 2 , Kimiko Kobayashi 2 , Masamichi Okubo 2 , Osamu Mimura 1 , Koichi Noguchi 2 1
Dept Ophthalmol, Hyogo College of Med, Nishinomiya, Japan; 2 Dept Anatomy and Neuroscience, Hyogo College of Med, Nishinomiya, Japan The ERM (ezrin, radixin, and moesin) proteins belong to the band-4.1 superfamily of membrane-cytoskeleton-linking proteins that bind to the actin cytoskeleton via their C-terminal sequences and bind to ERM binding membrane proteins. We investigated the expression and phosphorylation of the ERM in rat spinal cord with SNI, to assess the possible plastic changes such as glial activation or the neuronal circuitry changes in association with ERM proteins expression. SNI did not change the expression of ERM mRNAs, however immunohistochemistry revealed the increase of the phosphorylated ERM in activated microglia following peripheral nerve injury. Injury-induced phosphorylation of ERM in the activated microglia may be involved in the membrane ruffling or migration of microglia leading to the accumulation of the activated microglia in the dorsal horn.
Dept of Neurobiol and Anat, Nagoya City Univ, Nagoya, Japan; Neurosci and Cell Biol, Univ of Osaka, Osaka, Japan
doi:10.1016/j.neures.2009.09.1194
P3-d13 Dihydropyridine-sensitive L-type Ca2+ channels in the dorsal horn are involved in the spinal ventral root after-discharges evoked by nociceptive mechanical stimuli Shohei Yamamoto, Mitsuo Tanabe, Hideki Ono Lab. CNS Pharmacol., Grad. Sch. Pharm. Sci., Nagoya City University, Nagoya, Japan We have previously reported that nociceptive mechanical stimuli to the rat hindpaw evoke two types of ventral root discharges which increase during stimulation (during-discharges) and after cessation of stimulation (after-discharges). In the present study, the type of Ca2+ channels and the site of neurons involved in the generation of after-discharges were studied. Under anesthesia, ventral root discharges were recorded from the left L5 ventral root, and stimuli were applied to the plantar surface of the left hindpaw using a von Frey hair. Nicardipine but not other L-type Ca2+ channel blockers applied directly to the surface of the spinal cord selectively reduced the after-discharges but not during-discharges. Microinjected nicardipine into the dorsal horn but not into the ventral horn reduced the after-discharges. The present results suggest that dihydropyridine-sensitive L-type Ca2+ channels are involved in the generation of ventral root after-discharges induced by nociceptive mechanical stimuli. doi:10.1016/j.neures.2009.09.1195
P3-d14 Cold hyperalgesia in a rat model of trigeminal neuropathic pain Hiroko Urano 1,2 , Noriyuki Ozaki 1 , Yasuo Sugiura 1 2
P3-d11 T-type Ca2+ channels expression within DRG in inflammatory hyperalgesia Masaya Watanabe 1 , Takashi Ueda 1 , Yusuke Ishida 1 , Shoichi Shimada 2 1
contrast, the P/Q-type VDCC antagonist -agatoxin-IVA, which alone showed little or no effect on C-fiber-evoked FPs, strongly suppressed LTP induction. These results indicate different roles of spinal N- and P/Q-type VDCCs in normal and sensitized conditions.
1
doi:10.1016/j.neures.2009.09.1192
2
Dept of
T-type (low-voltage-activated) Ca2+ channels (Cav3.1, Cav3.2 and Cav3.3) activate with small depolarizations; they have key functions in generation and timing of action potential. They are expressed in small to medium-size cells in dorsal root ganglia (DRG). Numerous approaches have demonstrated the function of T-type Ca2+ channels in supporting acute peripheral nociceptive signals. Furthermore, recent pharmacological and gene-silencing studies revealed that T-type Ca2+ channels also contribute to symptoms of chronic pain associated with peripheral axonal injury. However, their involvement in development of inflammatory hyperalgesia is poorly understood. To address this issue, we made an experimental mouse model with unilateral inflammation generated by intraplantar injection of carrageenan into the right hind paw, and examined the mRNA expression of T-type Ca2+ channels in the DRG. The results suggested that T-type Ca2+ channels were involved in development of inflammatory hyperalgesia and extensive mechanisms of contralateral allodynia. doi:10.1016/j.neures.2009.09.1193
S215
Dept Func Anat & Neurosci, Grad Sch Med Nagoya Univ, Aichi, Japan; Dept Oral Physiol, Matsumoto Dent Univ, Nagano, Japan
Aim of the study: Trigeminal neuropathic pain is a facial pain syndrome associated with the trigeminal nerve injury. We validated a partial infraorbital nerve (IoN) ligation model by testing nociceptive responses to cold and mechanical stimuli. In addition, involvement of TRP channels on the cold hyperalgesia was investigated. Methods: The unilateral IoN was partially ligated by 6-0 silk. Withdrawal responses to mechanical and thermal stimuli to vibrissal pads (VP) were assessed by the use of von Frey filaments and a thermal stimulator equipped with Peltier-elements respectively. Changes in withdrawal responses were measured after subcutaneous injection of TRP channel antagonist capsazepine. Results: Mechanical allodynia and cold hyperalgesia were observed in VP ipsilateral to ligation. Capsazepine suppressed cold hyperalgesia, but not mechanical allodynia. Conclusion: A partial ligation of IoN was useful model of trigeminal neuropathic pain. TRP channel plays an important role in cold hyperalgesia observed in this model. doi:10.1016/j.neures.2009.09.1196
P3-d15 Aging reduced mechanical sensitivity of unmyelinated afferents electrically identified in the rat skin-saphenous nerve preparations in vitro Toru Taguchi, Hiroki Ota, Teru Matsuda, Shiori Murase, Kazue Mizumura Dept Neurosci II, Res Inst Environ Med, Nagoya University, Nagoya, Japan
P3-d12 Role of voltage-dependent calcium channels in spinal longterm potentiation of C-fiber-evoked field potentials Soichiro Ohnami 1,2 , Mitsuo Tanabe 1 , Syunji Shinohara 2 , Akira Kato 2 , Hideki Ono 1 1 2
Lab CNS Pharmacol, Grad Sch of Pharm Sci, Nagoya City Univ, Japan; Shionogi & Co, Ltd, Japan
Function of voltage-dependent calcium channels (VDCCs) is critical for nociceptive transmission in normal and pathological states. We investigated the role of VDCCs in long-term potentiation (LTP) of C-fiber-evoked field potentials (FPs) recorded in the rat spinal dorsal horn, which is a synaptic model of hypersensitivity underlying an increased efficacy of nociceptive transmission. When applied spinally either before or after establishment of LTP by high-frequency stimulation (HFS), the Ntype VDCC antagonist -conotoxin-GVIA (Ctx) produced prolonged inhibitions of C-fiber-evoked FPs and was more effective after LTP at a lower dose range. Ctx did not hamper induction of LTP, which was, however, maintained at a lower level. By
The aim of this study was to examine the changes by aging in the sensitivity of the cutaneous C-fiber afferents to mechanical and heat stimuli. A single C-fiber was identified by electrical stimulation of the nerve trunk in vitro in hind paw skinsaphenous nerve preparations excised from deeply anesthetized rats (Young: 9–14 w, n = 67, Aged: 129–138 w, n = 75). Ratio of fibers having a mechano-sensitive receptive field was significantly lower in the aged afferents (49% vs. 27%). Increased threshold and decreased response magnitude of the nociceptors to quantitative mechanical stimulation (196 mN in 20 s) was observed in the aged. Response to heat tended to be reduced in the aged. Mechanical withdrawal threshold measured with von Frey hairs applied to the plantar skin was not different between two age groups, while the withdrawal latency to noxious heat (Hargreaves test) was shortened in the aged. These results suggest that the central processing of the nociceptive information is also changed with aging. doi:10.1016/j.neures.2009.09.1197
P3-d10 Expression and phosphorylation of ERM family proteins in rat spinal dorsal horn with spared nerve injury (SNI) model Ryosuke Kashimoto 1 , Hiroki Yamanaka 2 , Kimiko Kobayashi 2 , Masamichi Okubo 2 , Osamu Mimura 1 , Koichi Noguchi 2 1
Dept Ophthalmol, Hyogo College of Med, Nishinomiya, Japan; 2 Dept Anatomy and Neuroscience, Hyogo College of Med, Nishinomiya, Japan The ERM (ezrin, radixin, and moesin) proteins belong to the band-4.1 superfamily of membrane-cytoskeleton-linking proteins that bind to the actin cytoskeleton via their C-terminal sequences and bind to ERM binding membrane proteins. We investigated the expression and phosphorylation of the ERM in rat spinal cord with SNI, to assess the possible plastic changes such as glial activation or the neuronal circuitry changes in association with ERM proteins expression. SNI did not change the expression of ERM mRNAs, however immunohistochemistry revealed the increase of the phosphorylated ERM in activated microglia following peripheral nerve injury. Injury-induced phosphorylation of ERM in the activated microglia may be involved in the membrane ruffling or migration of microglia leading to the accumulation of the activated microglia in the dorsal horn.
Dept of Neurobiol and Anat, Nagoya City Univ, Nagoya, Japan; Neurosci and Cell Biol, Univ of Osaka, Osaka, Japan
doi:10.1016/j.neures.2009.09.1194
P3-d13 Dihydropyridine-sensitive L-type Ca2+ channels in the dorsal horn are involved in the spinal ventral root after-discharges evoked by nociceptive mechanical stimuli Shohei Yamamoto, Mitsuo Tanabe, Hideki Ono Lab. CNS Pharmacol., Grad. Sch. Pharm. Sci., Nagoya City University, Nagoya, Japan We have previously reported that nociceptive mechanical stimuli to the rat hindpaw evoke two types of ventral root discharges which increase during stimulation (during-discharges) and after cessation of stimulation (after-discharges). In the present study, the type of Ca2+ channels and the site of neurons involved in the generation of after-discharges were studied. Under anesthesia, ventral root discharges were recorded from the left L5 ventral root, and stimuli were applied to the plantar surface of the left hindpaw using a von Frey hair. Nicardipine but not other L-type Ca2+ channel blockers applied directly to the surface of the spinal cord selectively reduced the after-discharges but not during-discharges. Microinjected nicardipine into the dorsal horn but not into the ventral horn reduced the after-discharges. The present results suggest that dihydropyridine-sensitive L-type Ca2+ channels are involved in the generation of ventral root after-discharges induced by nociceptive mechanical stimuli. doi:10.1016/j.neures.2009.09.1195
P3-d14 Cold hyperalgesia in a rat model of trigeminal neuropathic pain Hiroko Urano 1,2 , Noriyuki Ozaki 1 , Yasuo Sugiura 1 2
P3-d11 T-type Ca2+ channels expression within DRG in inflammatory hyperalgesia Masaya Watanabe 1 , Takashi Ueda 1 , Yusuke Ishida 1 , Shoichi Shimada 2 1
contrast, the P/Q-type VDCC antagonist -agatoxin-IVA, which alone showed little or no effect on C-fiber-evoked FPs, strongly suppressed LTP induction. These results indicate different roles of spinal N- and P/Q-type VDCCs in normal and sensitized conditions.
1
doi:10.1016/j.neures.2009.09.1192
2
Dept of
T-type (low-voltage-activated) Ca2+ channels (Cav3.1, Cav3.2 and Cav3.3) activate with small depolarizations; they have key functions in generation and timing of action potential. They are expressed in small to medium-size cells in dorsal root ganglia (DRG). Numerous approaches have demonstrated the function of T-type Ca2+ channels in supporting acute peripheral nociceptive signals. Furthermore, recent pharmacological and gene-silencing studies revealed that T-type Ca2+ channels also contribute to symptoms of chronic pain associated with peripheral axonal injury. However, their involvement in development of inflammatory hyperalgesia is poorly understood. To address this issue, we made an experimental mouse model with unilateral inflammation generated by intraplantar injection of carrageenan into the right hind paw, and examined the mRNA expression of T-type Ca2+ channels in the DRG. The results suggested that T-type Ca2+ channels were involved in development of inflammatory hyperalgesia and extensive mechanisms of contralateral allodynia. doi:10.1016/j.neures.2009.09.1193
S215
Dept Func Anat & Neurosci, Grad Sch Med Nagoya Univ, Aichi, Japan; Dept Oral Physiol, Matsumoto Dent Univ, Nagano, Japan
Aim of the study: Trigeminal neuropathic pain is a facial pain syndrome associated with the trigeminal nerve injury. We validated a partial infraorbital nerve (IoN) ligation model by testing nociceptive responses to cold and mechanical stimuli. In addition, involvement of TRP channels on the cold hyperalgesia was investigated. Methods: The unilateral IoN was partially ligated by 6-0 silk. Withdrawal responses to mechanical and thermal stimuli to vibrissal pads (VP) were assessed by the use of von Frey filaments and a thermal stimulator equipped with Peltier-elements respectively. Changes in withdrawal responses were measured after subcutaneous injection of TRP channel antagonist capsazepine. Results: Mechanical allodynia and cold hyperalgesia were observed in VP ipsilateral to ligation. Capsazepine suppressed cold hyperalgesia, but not mechanical allodynia. Conclusion: A partial ligation of IoN was useful model of trigeminal neuropathic pain. TRP channel plays an important role in cold hyperalgesia observed in this model. doi:10.1016/j.neures.2009.09.1196
P3-d15 Aging reduced mechanical sensitivity of unmyelinated afferents electrically identified in the rat skin-saphenous nerve preparations in vitro Toru Taguchi, Hiroki Ota, Teru Matsuda, Shiori Murase, Kazue Mizumura Dept Neurosci II, Res Inst Environ Med, Nagoya University, Nagoya, Japan
P3-d12 Role of voltage-dependent calcium channels in spinal longterm potentiation of C-fiber-evoked field potentials Soichiro Ohnami 1,2 , Mitsuo Tanabe 1 , Syunji Shinohara 2 , Akira Kato 2 , Hideki Ono 1 1 2
Lab CNS Pharmacol, Grad Sch of Pharm Sci, Nagoya City Univ, Japan; Shionogi & Co, Ltd, Japan
Function of voltage-dependent calcium channels (VDCCs) is critical for nociceptive transmission in normal and pathological states. We investigated the role of VDCCs in long-term potentiation (LTP) of C-fiber-evoked field potentials (FPs) recorded in the rat spinal dorsal horn, which is a synaptic model of hypersensitivity underlying an increased efficacy of nociceptive transmission. When applied spinally either before or after establishment of LTP by high-frequency stimulation (HFS), the Ntype VDCC antagonist -conotoxin-GVIA (Ctx) produced prolonged inhibitions of C-fiber-evoked FPs and was more effective after LTP at a lower dose range. Ctx did not hamper induction of LTP, which was, however, maintained at a lower level. By
The aim of this study was to examine the changes by aging in the sensitivity of the cutaneous C-fiber afferents to mechanical and heat stimuli. A single C-fiber was identified by electrical stimulation of the nerve trunk in vitro in hind paw skinsaphenous nerve preparations excised from deeply anesthetized rats (Young: 9–14 w, n = 67, Aged: 129–138 w, n = 75). Ratio of fibers having a mechano-sensitive receptive field was significantly lower in the aged afferents (49% vs. 27%). Increased threshold and decreased response magnitude of the nociceptors to quantitative mechanical stimulation (196 mN in 20 s) was observed in the aged. Response to heat tended to be reduced in the aged. Mechanical withdrawal threshold measured with von Frey hairs applied to the plantar skin was not different between two age groups, while the withdrawal latency to noxious heat (Hargreaves test) was shortened in the aged. These results suggest that the central processing of the nociceptive information is also changed with aging. doi:10.1016/j.neures.2009.09.1197