Differential roles of galanin on mechanical and cooling responses at the primary afferent nociceptor
<p>Abstract</p> <p>Background</p> <p>Galanin is expressed in a small percentage of intact small diameter sensory neurons of the dorsal root ganglia and in the afferent terminals of the superficial lamina of the dorsal horn of the spinal cord. The neuropeptide modulates...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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SAGE Publishing
2012-06-01
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| Series: | Molecular Pain |
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| Online Access: | http://www.molecularpain.com/content/8/1/41 |
| _version_ | 1819027809693073408 |
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| author | Hulse Richard P Donaldson Lucy F Wynick David |
| author_facet | Hulse Richard P Donaldson Lucy F Wynick David |
| author_sort | Hulse Richard P |
| collection | DOAJ |
| description | <p>Abstract</p> <p>Background</p> <p>Galanin is expressed in a small percentage of intact small diameter sensory neurons of the dorsal root ganglia and in the afferent terminals of the superficial lamina of the dorsal horn of the spinal cord. The neuropeptide modulates nociception demonstrating dose-dependent pro- and anti-nociceptive actions in the naïve animal. Galanin also plays an important role in chronic pain, with the anti-nociceptive actions enhanced in rodent neuropathic pain models. In this study we compared the role played by galanin and its receptors in mechanical and cold allodynia by identifying individual rat C-fibre nociceptors and characterising their responses to mechanical or acetone stimulation.</p> <p>Results</p> <p>Mechanically evoked responses in C-fibre nociceptors from naive rats were sensitised after close intra-arterial infusion of galanin or Gal2-11 (a galanin receptor-2/3 agonist) confirming previous data that galanin modulates nociception <it>via</it> activation of GalR2. In contrast, the same dose and route of administration of galanin, but not Gal2-11, inhibited acetone and menthol cooling evoked responses, demonstrating that this inhibitory mechanism is not mediated by activation of GalR2. We then used the partial saphenous nerve ligation injury model of neuropathic pain (PSNI) and the complete Freund’s adjuvant model of inflammation in the rat and demonstrated that close intra-arterial infusion of galanin, but not Gal2-11, reduced cooling evoked nociceptor activity and cooling allodynia in both paradigms, whilst galanin and Gal2-11 both decreased mechanical activation thresholds. A previously described transgenic mouse line which inducibly over-expresses galanin (Gal-OE) after nerve injury was then used to investigate whether manipulating the levels of endogenous galanin also modulates cooling evoked nociceptive behaviours after PSNI. Acetone withdrawal behaviours in naive mice showed no differences between Gal-OE and wildtype (WT) mice. 7-days after PSNI Gal-OE mice demonstrated a significant reduction in the duration of acetone-induced nociceptive behaviours compared to WT mice.</p> <p>Conclusions</p> <p>These data identify a novel galaninergic mechanism that inhibits cooling evoked neuronal activity and nociceptive behaviours <it>via</it> a putative GalR1 mode of action that would also be consistent with a TRP channel-dependent mechanism.</p> |
| first_indexed | 2024-12-21T05:48:22Z |
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| institution | Directory Open Access Journal |
| issn | 1744-8069 |
| language | English |
| last_indexed | 2024-12-21T05:48:22Z |
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| series | Molecular Pain |
| spelling | doaj.art-160814dd14584100aa76b3061f0429052022-12-21T19:14:03ZengSAGE PublishingMolecular Pain1744-80692012-06-01814110.1186/1744-8069-8-41Differential roles of galanin on mechanical and cooling responses at the primary afferent nociceptorHulse Richard PDonaldson Lucy FWynick David<p>Abstract</p> <p>Background</p> <p>Galanin is expressed in a small percentage of intact small diameter sensory neurons of the dorsal root ganglia and in the afferent terminals of the superficial lamina of the dorsal horn of the spinal cord. The neuropeptide modulates nociception demonstrating dose-dependent pro- and anti-nociceptive actions in the naïve animal. Galanin also plays an important role in chronic pain, with the anti-nociceptive actions enhanced in rodent neuropathic pain models. In this study we compared the role played by galanin and its receptors in mechanical and cold allodynia by identifying individual rat C-fibre nociceptors and characterising their responses to mechanical or acetone stimulation.</p> <p>Results</p> <p>Mechanically evoked responses in C-fibre nociceptors from naive rats were sensitised after close intra-arterial infusion of galanin or Gal2-11 (a galanin receptor-2/3 agonist) confirming previous data that galanin modulates nociception <it>via</it> activation of GalR2. In contrast, the same dose and route of administration of galanin, but not Gal2-11, inhibited acetone and menthol cooling evoked responses, demonstrating that this inhibitory mechanism is not mediated by activation of GalR2. We then used the partial saphenous nerve ligation injury model of neuropathic pain (PSNI) and the complete Freund’s adjuvant model of inflammation in the rat and demonstrated that close intra-arterial infusion of galanin, but not Gal2-11, reduced cooling evoked nociceptor activity and cooling allodynia in both paradigms, whilst galanin and Gal2-11 both decreased mechanical activation thresholds. A previously described transgenic mouse line which inducibly over-expresses galanin (Gal-OE) after nerve injury was then used to investigate whether manipulating the levels of endogenous galanin also modulates cooling evoked nociceptive behaviours after PSNI. Acetone withdrawal behaviours in naive mice showed no differences between Gal-OE and wildtype (WT) mice. 7-days after PSNI Gal-OE mice demonstrated a significant reduction in the duration of acetone-induced nociceptive behaviours compared to WT mice.</p> <p>Conclusions</p> <p>These data identify a novel galaninergic mechanism that inhibits cooling evoked neuronal activity and nociceptive behaviours <it>via</it> a putative GalR1 mode of action that would also be consistent with a TRP channel-dependent mechanism.</p>http://www.molecularpain.com/content/8/1/41GalaninPrimary afferentColdNeuropathic painInflammatory pain |
| spellingShingle | Hulse Richard P Donaldson Lucy F Wynick David Differential roles of galanin on mechanical and cooling responses at the primary afferent nociceptor Molecular Pain Galanin Primary afferent Cold Neuropathic pain Inflammatory pain |
| title | Differential roles of galanin on mechanical and cooling responses at the primary afferent nociceptor |
| title_full | Differential roles of galanin on mechanical and cooling responses at the primary afferent nociceptor |
| title_fullStr | Differential roles of galanin on mechanical and cooling responses at the primary afferent nociceptor |
| title_full_unstemmed | Differential roles of galanin on mechanical and cooling responses at the primary afferent nociceptor |
| title_short | Differential roles of galanin on mechanical and cooling responses at the primary afferent nociceptor |
| title_sort | differential roles of galanin on mechanical and cooling responses at the primary afferent nociceptor |
| topic | Galanin Primary afferent Cold Neuropathic pain Inflammatory pain |
| url | http://www.molecularpain.com/content/8/1/41 |
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