Comparison of the capsaicin- and amino acid-sensitivity of dorsal root C fibres in the rat and the toad

Hawkins, Neil; Hearn, Joe W.; Evans, Richard H.

doi:10.1016/0742-8413(91)90279-3

Cited by 8 publications

(5 citation statements)

References 8 publications

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“…We showed that naked mole-rats are behaviorally insensitive to capsaicin. Birds and amphibians are also insensitive to capsaicin [ 10 , 56 ], and the avian TRPV1 gene encodes a proton- and heat-sensitive channel that is not activated by capsaicin, which explains behavioral insensitivity in this species [ 10 ]. It thus appears that the capsaicin sensitivity of TRPV1 is an attribute gained in higher vertebrates during the course of evolution.…”

Section: Discussionmentioning

confidence: 99%

Selective Inflammatory Pain Insensitivity in the African Naked Mole-Rat (Heterocephalus glaber)

et al. 2008

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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.

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Section: Discussionmentioning

confidence: 99%

Selective Inflammatory Pain Insensitivity in the African Naked Mole-Rat (Heterocephalus glaber)

et al. 2008

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“…Other in vitro studies give further evidence for glutamate’s activation/sensitization of primary afferents and KARs have been explored as one of the ionotropic EAARs producing these responses (Davies et al, 1979; Evans, 1980, 1985; Agrawal & Evans, 1986; Hawkins et al, 1991; Du et al, 2006). A number of studies in rats, toads, and frogs show that glutamate and kainate depolarize primary afferents in dorsal roots (Davies et al, 1979; Evans, 1980, 1985; Agrawal & Evans, 1986; Hawkins et al, 1991; Pook et al, 1993).…”

Section: Peripheral Effects Of Glutamate: Electrophysiology (Table 1)mentioning

confidence: 99%

“…A number of studies in rats, toads, and frogs show that glutamate and kainate depolarize primary afferents in dorsal roots (Davies et al, 1979; Evans, 1980, 1985; Agrawal & Evans, 1986; Hawkins et al, 1991; Pook et al, 1993). Isolated dorsal roots from neonatal rats are depolarized selectively by L-glutamate and kainate and blocked by CNQX and NBQX.…”

Section: Peripheral Effects Of Glutamate: Electrophysiology (Table 1)mentioning

confidence: 99%

Glutamate pharmacology and metabolism in peripheral primary afferents: Physiological and pathophysiological mechanisms

Miller

Hoffman

Sutharshan

et al. 2011

Pharmacology & Therapeutics

121

129

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In addition to using glutamate as a neurotransmitter at central synapses, many primary sensory neurons release glutamate from peripheral terminals. Primary sensory neurons with cell bodies in dorsal root or trigeminal ganglia produce glutaminase, the synthetic enzyme for glutamate, and transport the enzyme in mitochondria to peripheral terminals. Vesicular glutamate transporters fill neurotransmitter vesicles with glutamate and they are shipped to peripheral terminals. Intense noxious stimuli or tissue damage causes glutamate to be released from peripheral afferent nerve terminals and augmented release occurs during acute and chronic inflammation. The site of action for glutamate can be at the autologous or nearby nerve terminals. Peripheral nerve terminals contain both ionotropic and metabotropic excitatory amino acid receptors (EAARs) and activation of these receptors can lower the activation threshold and increase the excitability of primary afferents. Antagonism of EAARs can reduce excitability of activated afferents and produce antinociception in many animal models of acute and chronic pain. Glutamate injected into human skin and muscle causes acute pain. Trauma in humans, such as arthritis, myalgia, and tendonitis, elevates glutamate levels in affected tissues. There is evidence that EAAR antagonism at peripheral sites can provide relief in some chronic pain sufferers.

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“…Facial nerves (N VII) of catfish (Ictalurus punctatus) are insensitive to 0.1% CAP (B. Bryant, unpublished data). Similarly, dorsal root nerve fibers in toads (Bufo bufo) were unresponsive to CAP up to concentrations of 430·µmol·l -1 , which is a concentration highly stimulatory to mammals (Hawkins et al, 1991). Brown treesnakes (Boiga irregularis) were behaviorally insensitive to ocular application of 1% oleoresin of Capsicum (estimated 100·p.p.m.…”

Section: Experiments 3 Ion Dependence Of Neuronal Sensitivitymentioning

confidence: 99%

Calcium responses of chicken trigeminal ganglion neurons to methyl anthranilate and capsaicin

Kirifides

Kurnellas

Clark

et al. 2004

Journal of Experimental Biology

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Comparison of the capsaicin- and amino acid-sensitivity of dorsal root C fibres in the rat and the toad

Cited by 8 publications

References 8 publications

Selective Inflammatory Pain Insensitivity in the African Naked Mole-Rat (Heterocephalus glaber)

Selective Inflammatory Pain Insensitivity in the African Naked Mole-Rat (Heterocephalus glaber)

Glutamate pharmacology and metabolism in peripheral primary afferents: Physiological and pathophysiological mechanisms

Calcium responses of chicken trigeminal ganglion neurons to methyl anthranilate and capsaicin

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