Peripheral voltage-gated calcium channels in skin are essential for transient neurogenic thermal hyperalgesia in mice (original) (raw)
Related papers
European Journal of Neuroscience, 1999
Capsaicin (CAPS) as well as acidic pH induces Ca 2+ in¯ux in a subset of rat dorsal root ganglion neurons. Here we show that CAPS as well as three different approaches to induce experimental tissue acidi®cation (phosphate buffered solution pH 5.4, CO 2 -gassed solution pH 6.1 and NPE-caged protons) yielded a transient heat sensitization of peripheral nociceptive terminals in rat skin in vitro. The heat sensitization induced by CAPS (1 mM) could be prevented by preloading the neurons with the neuroprotective calcium chelator BAPTA-AM (1 mM). However, this pretreatment had no effect on the sensitization following exposure to acidic solutions (pH 5.4 and pH 6.1). Therefore, the membrane-permeant proton buffer SNARF-AM (200 mM) was used together with BAPTA-AM in order to prevent changes in intracellular pH. Under these conditions heat sensitization by low pH did not occur. To investigate the underlying membrane mechanisms, current recordings together with simultaneous calcium measurements using FURA-2 were performed in neurons isolated from rat dorsal root ganglia. In a subset of these neurons, an increase in [Ca 2+ ] i and concomitant facilitation of heat-activated ionic currents was observed after application of CAPS as well as pH 5.6. Rises in [Ca 2+ ] i thus appear to play an essential role in plastic changes not only of central neurons but also of peripheral nociceptive terminals which may account for heat hyperalgesia.
Pain sensitivity in mice lacking the Cav2.1α1 subunit of P/Q-type Ca2+ channels
Neuroscience, 2006
The role of voltage-gated Ca 2؉ (Ca V ) channels in pain mechanisms has been the object of intense investigation using pharmacological approaches and, more recently, using mutant mouse models lacking the Ca V ␣ l pore-forming subunit of N-, R-and T-type channels. The role of P/Q-type channels in nociception and pain transmission has been investigated by pharmacological approaches but remains to be fully elucidated. To address this issue, we have analyzed pain-related behavioral responses of null mutant mice for the Ca V 2.1␣ 1 subunit of P/Q-type channels. Homozygous null mutant Ca V 2.1␣ 1 ؊/؊ mice developed dystonia at 10 -12 days after birth and did not survive past weaning. Tested at ages where motor deficit was either absent or very mild, Ca V 2.1␣ 1 ؊/؊ mice showed reduced tail withdrawal latencies in the tail-flick test and reduced abdominal writhes in the acetic acid writhing test. Adult heterozygous Ca V 2.1␣ 1 ؉/؊ mice did not show motor deficits in the rotarod and activity cage tests and did not show alterations in pain responses in the tail-flick test and the acetic acid writhing test. Strikingly, they showed a reduced licking response during the second phase of formalin-induced inflammatory pain and a reduced mechanical allodynia in the chronic constriction injury model of neuropathic pain. Our findings show that P/Q-type channels play an antinociceptive role in sensitivity to non-injurious noxious thermal stimuli and a pronociceptive role in inflammatory and neuropathic pain states, pointing to an important role of Ca V 2.1 channels in central sensitization.
Inflammatory Pain: The Cellular Basis of Heat Hyperalgesia
Current Neuropharmacology, 2006
Injury or inflammation release a range of inflammatory mediators that increase the sensitivity of sensory neurons to noxious thermal or mechanical stimuli. The heat-and capsaicin-gated channel TRPV1, which is an important detector of multiple noxious stimuli, plays a critical role in the development of thermal hyperalgesia induced by a wide range of inflammatory mediators. We review here recent findings on the molecular mechanisms of sensitisation of TRPV1 by inflammatory mediators, including bradykinin, ATP, NGF and prostaglandins. We describe the signalling pathways believed to be involved in the potentiation of TRPV1, and our current understanding of how inflammatory mediators couple to these pathways.
Embo Journal, 2005
Analgesic therapies are still limited and sometimes poorly effective, therefore finding new targets for the development of innovative drugs is urgently needed. In order to validate the potential utility of blocking T-type calcium channels to reduce nociception, we explored the effects of intrathecally administered oligodeoxynucleotide antisenses, specific to the recently identified T-type calcium channel family (Ca V 3.1, Ca V 3.2, and Ca V 3.3), on reactions to noxious stimuli in healthy and mononeuropathic rats. Our results demonstrate that the antisense targeting Ca V 3.2 induced a knockdown of the Ca V 3.2 mRNA and protein expression as well as a large reduction of 'Ca V 3.2like' T-type currents in nociceptive dorsal root ganglion neurons. Concomitantly, the antisense treatment resulted in major antinociceptive, anti-hyperalgesic, and anti-allodynic effects, suggesting that Ca V 3.2 plays a major pronociceptive role in acute and chronic pain states. Taken together, the results provide direct evidence linking Ca V 3.2 T-type channels to pain perception and suggest that Ca V 3.2 may offer a specific molecular target for the treatment of pain.
2021
Background and Purpose T-type calcium channels, mainly the Cav3.2 subtype, are important contributors to the nociceptive signaling pathway. We investigated their involvement in inflammation and related pain-like symptoms. Experimental Approach The involvement of Cav3.2 and T-type channels was investigated using genetic and pharmacological inhibition to assess mechanical allodynia/hyperalgesia and edema development in two murine inflammatory pain models. The location of Cav3.2 involved in pain-like symptoms was studied in mice with Cav3.2 knocked out in C-low threshold mechanoreceptors (C-LTMR) and the use of ABT-639, a peripherally restricted T-type channel inhibitor. The anti-edematous effect of Cav3.2 inhibition was investigated in chimeric mice with immune cells deleted for Cav3.2. Lymphocytes and macrophages from either green fluorescent protein-targeted Cav3.2 or KO mice were used to determine the expression of Cav3.2 protein and the functional status of the cells. Key Results ...
Thermal nociception and TRPV1 function are attenuated in mice lacking the nucleotide receptor P2Y2
PAIN, 2008
Recent studies indicate that ATP and UTP act at G protein-coupled (P2Y) nucleotide receptors to excite nociceptive sensory neurons; nucleotides also potentiate signaling through the pro-nociceptive capsaicin receptor, TRPV1. We demonstrate here that P2Y 2 is the principal UTP receptor in somatosensory neurons: P2Y 2 is highly expressed in dorsal root ganglia and P2Y 2 (−/−) mice showed profound deficits in UTP-evoked calcium transients and potentiation of capsaicin responses. P2Y 2 (−/−) mice were also deficient in the detection of painful heat: baseline thermal response latencies were increased and mutant mice failed to develop thermal hypersensitivity in response to inflammatory injury (injection of complete Freund's adjuvant into the hindpaw). P2Y 2 was the only Gq-coupled P2Y receptor examined that showed an increase in DRG mRNA levels in response to inflammation. Surprisingly, TRPV1 function was also attenuated in P2Y 2 (−/−) mice, as measured by the frequency and magnitude of capsaicin responses in vitro and behavioral responses to capsaicin administration in vivo. However, TRPV1 mRNA levels and immunoreactivity were not reduced, and behavioral sensitivity to capsaicin could be largely restored in P2Y 2 (−/−) mice by pretreatment with bradykinin, suggesting that normal function of TRPV1 requires ongoing modulation by G proteincoupled receptors. These results indicate that nucleotide signaling through P2Y 2 plays a key role in thermal nociception.
Science Signaling
Pain-sensing sensory neurons of the dorsal root ganglion (DRG) can become sensitized or hyperexcitable in response to surgically induced peripheral tissue injury. We investigated the potential role and molecular mechanisms of nociceptive ion channel dysregulation in acute pain conditions such as those resulting from skin and soft tissue incision. We used selective pharmacology, electrophysiology, and mouse genetics to link increased current densities arising from the Ca V 3.2 isoform of T-type calcium channels (T-channels) to nociceptive sensitization using a clinically relevant rodent model of skin and deep tissue incision. Furthermore, knockdown of the Ca V 3.2-targeting deubiquitinating enzyme USP5 or disruption of USP5 binding to Ca V 3.2 channels in peripheral nociceptors resulted in a robust antihyperalgesic effect in vivo and substantial T-current reduction in vitro. Our study provides mechanistic insight into the role of plasticity in Ca V 3.2 channel activity after surgical incision and identifies potential targets for perioperative pain that may greatly decrease the need for narcotics and potential for drug abuse.
Neuropharmacology, 2013
Pha1b toxin is a peptide purified from the venom of the armed spider Phoneutria nigriventer, with markedly antinociceptive action in models of acute and persistent pain in rats. Similarly to ziconotide, its analgesic action is related to inhibition of high voltage activated calcium channels with more selectivity for N-type. In this study we evaluated the effect of Pha1b when injected peripherally or intrathecally in a rat model of spontaneous pain induced by capsaicin. We also investigated the effect of Pha1b on Ca 2þ transients in cultured dorsal root ganglia (DRG) neurons and HEK293 cells expressing the TRPV1 receptor. Intraplantar or intrathecal administered Pha1b reduced both nocifensive behavior and mechanical hypersensitivity induced by capsaicin similarly to that observed with SB366791, a specific TRPV1 antagonist. Peripheral nifedipine and mibefradil did also decrease nociceptive behavior induced by intraplantar capsaicin. In contrast, u-conotoxin MVIIA (a selective N-type Ca 2þ channel blocker) was effective only when administered intrathecally. Pha1b, MVIIA and SB366791 inhibited, with similar potency, the capsaicin-induced Ca 2þ transients in DRG neurons. The simultaneous administration of Pha1b and SB366791 inhibited the capsaicin-induced Ca 2þ transients that were additive suggesting that they act through different targets. Moreover, Pha1b did not inhibit capsaicin-activated currents in patchclamp recordings of HEK293 cells that expressed TRPV1 receptors. Our results show that Pha1b may be effective as a therapeutic strategy for pain and this effect is not related to the inhibition of TRPV1 receptors.