PMID:18232734
| Citation |
Park, TJ, Lu, Y, Jüttner, R, Smith, ES, Hu, J, Brand, A, Wetzel, C, Milenkovic, N, Erdmann, B, Heppenstall, PA, Laurito, CE, Wilson, SP and Lewin, GR (2008) Selective inflammatory pain insensitivity in the African naked mole-rat (Heterocephalus glaber). PLoS Biol. 6:e13 |
|---|---|
| Abstract |
In all mammals, tissue inflammation leads to pain and behavioral sensitization to thermal and mechanical stimuli called hyperalgesia. We studied pain mechanisms in the African naked mole-rat, an unusual rodent species that lacks pain-related neuropeptides (e.g., substance P) in cutaneous sensory fibers. Naked mole-rats show a unique and remarkable lack of pain-related behaviors to two potent algogens, acid and capsaicin. Furthermore, when exposed to inflammatory insults or known mediators, naked mole-rats do not display thermal hyperalgesia. In contrast, naked mole-rats do display nocifensive behaviors in the formalin test and show mechanical hyperalgesia after inflammation. Using electrophysiology, we showed that primary afferent nociceptors in naked mole-rats are insensitive to acid stimuli, consistent with the animal's lack of acid-induced behavior. Acid transduction by sensory neurons is observed in birds, amphibians, and fish, which suggests that this tranduction mechanism has been selectively disabled in the naked mole-rat in the course of its evolution. In contrast, nociceptors do respond vigorously to capsaicin, and we also show that sensory neurons express a transient receptor potential vanilloid channel-1 ion channel that is capsaicin sensitive. Nevertheless, the activation of capsaicin-sensitive sensory neurons in naked mole-rats does not produce pain-related behavior. We show that capsaicin-sensitive nociceptors in the naked mole-rat are functionally connected to superficial dorsal horn neurons as in mice. However, the same nociceptors are also functionally connected to deep dorsal horn neurons, a connectivity that is rare in mice. The pain biology of the naked mole-rat is unique among mammals, thus the study of pain mechanisms in this unusual species can provide major insights into what constitutes "normal" mammalian nociception. |
| Links |
PubMed PMC2214810 Online version:10.1371/journal.pbio.0060013 |
| Keywords |
Acids/pharmacology; Animals; Capsaicin/pharmacology; Hyperalgesia/chemically induced; Inflammation; Mole Rats; Neurons, Afferent; Nociceptors/drug effects; Pain/physiopathology; Pain/psychology; Pain Measurement; Pain Threshold/physiology; Posterior Horn Cells |
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