Capsaicin-induced effects on c-fos expression and NADPH-diaphorase activity in the feline spinal cord

https://doi.org/10.1016/j.ejphar.2005.08.006Get rights and content

Abstract

The distribution of c-fos expression and NADPH-diaphorase reactivity in the cervical and lumbar segments after stimulation of the vanilloid receptors in the dorsal neck muscles with capsaicin was studied in cats anaesthetized with α-chloralose. After the unilateral intramuscular injection of capsaicin, the mean number of Fos-immunoreactive neurons detected with an avidin–biotin–peroxidase technique was significantly increased in the superficial laminae (I), neck of the dorsal horn (V), and area around the central canal (VII) within both the cervical and lumbar spinal cord. Most Fos-immunoreactive neurons in the cervical spinal cord were giant and small cells. The widespread distribution of Fos-immunoreactive cells throughout the cervical cord within the intermediate zone (VII) coincided with the sites of localization of last-order premotor interneurons and cells of origin of inter-segmental crossed and uncrossed descending propriospinal pathways to the lumbar spinal cord. Fos-immunoreactive neurons were co-distributed with nitric oxide-generating cells at both levels of the spinal cord, although the double-labeled cells were not observed. In conclusion, the analysis of c-fos expression and NADPH-diaphorase reactivity shows that stimulation of vanilloid receptors in the neck muscles can initiate distinctive neuronal plasticity in the cervical (C1–C8) and lumbar (L1–L7) segments, and confirms the anatomical and functional coupling of both regions during processing of nociceptive signals from the dorsal neck muscles.

Introduction

Capsaicin is prototypic vanilloid receptor agonist which is now widely used as pharmacological tool to induce experimental models of acute skeletal muscle pain in animal and human (Sluka and Willis, 1998, Herbert and Holzer, 2002), as well as the therapeutic agent in clinical trials (Watson et al., 1993). Although capsaicin initially stimulates glutamate and neuropeptide release, it also induces a sustained inhibitory effects that are manifested in its analgesia and anti-inflammatory actions (Winter et al., 1995). The vanilloid receptor (TRPV1) is molecular target responding to noxious heat and protons (Caterina, 2003), and expressed in predominant (85%) of substance P-containing primary afferent fibers. In skeletal muscles such type of receptors could be activated during myositis accompanied with increase of tissue temperature, sustained contraction, hypoxia or injury. Intramuscular injections of capsaicin in humans have been shown to induce a deep pain of typical intensity profile, and that is characterized by referred pain and hyperalgesia (Graven-Nielsen and Mense, 2001). It was shown that capsaicin could stimulate predominantly group IV muscle afferents (Kaufman et al., 1982), and capsaicin-sensitive fibers activate spinal inhibitory pathways which attenuate motoneuronal output during muscle fatigue (Pettorossi et al., 1999, Kalezic et al., 2004a, Kostyukov et al., 2005). However, the spinal circuits that involved into nociceptive processing followed by activation of vanilloid receptors in the neck muscles are not still detailed. Immunohistochemical method of c-fos expression as a marker of neuronal activation can be fruitful to study the intra- and inter-segmental pathways involved into nociception. It was shown that the chemical or mechanical activation of Aδ and C (group III and IV) primary muscle afferents induced c-fos expression in the spinal neurons (Harris, 1998, King and Apps, 2000, Pilyavskii et al., 2001, Buritova and Besson, 2002).

Capsaicin activates a number of biochemical systems and increases concentration of nitric oxide (NO) in tissue (Bauer et al., 1995). It is well documented that nitric oxide synthase (NOS) that is presented in some spinal neurons can be expressed in a much greater number of central neurons and, additionally, in glial cells during acute pain, hyperalgesia, inflammation or muscle fatigue development (Herdegen et al., 1994, Vizzard et al., 1995, Maisky et al., 2002). Recent findings demonstrate that endogenous NO may modulate the activity of group IV muscle afferents (Arbogast et al., 2001, Urch and Dickenson, 2003), and may be involved in the mechanisms of capsaicin-induced nociceptive response (Sakurada et al., 1996).

In an attempt to further elucidate the spinal circuits that convey the signals from muscle nociceptors, we set out to test the hypothesis that persistent stimulation of vanilloid receptors in the feline dorsal neck muscles by capsaicin can induce distinctive patterns of Fos-immunoreactivity and NADPH-diaphorase reactivity within both the cervical and lumbar spinal cord. Neuroanatomical data about pathways from capsaicin-sensitive neck muscle afferents to the cervical and lumbar spinal cord are presented in this study preliminary data were published elsewhere (Kalezic et al., 2004b).

Section snippets

Experimental groups and pain stimulation protocol

Twelve cats of either sex (2.5–3.0 kg) were used in these experiments: (1) control group, without preceding injections (n = 3); (2) vehicle-injected group (n = 3); (3) capsaicin-treated group (n = 6). The pain stimulation protocol and the handling of the animals were performed in accordance with the European Communities Council Directive of 24 November 1986 (86/609/EEC). Animals of all experimental groups were anaesthetized (α-chloralose 50 mg/kg i.p.). In animals of a treated group, capsaicin

Results

In the intact cats, the basal level of c-fos expression on the both sides of the cervical and lumbar spinal cord was very low (one or two Fos-immunoreactive neurons per 30 μm thick section). Although, in the vehicle-injected cats the number of Fos-immunoreactive neurons was found to increase bilaterally in the rostral cervical and lumbar segments as response to injection-related pain. For example, in the C3/C4 and L4/L5 segments, the mean number of labeled neurons rose to 5.8 ± 0.9 (n = 3) and 3.5 ± 

Discussion

The findings presented here demonstrate that the selective stimulation of vanilloid receptors in the dorsal neck muscles initiates the neuronal plasticity in both cervical and lumbar spinal segments. The plastic changes are characterized by a significant increase in the number of Fos-immunoreactive neurons in the C1–C8 segments, predominantly on the ipsilateral (injected) side. However, in the lumbar segments, there is a marked bilateral rise in the number of labeled cells. The defined labeling

Acknowledgment

This study was supported by the Royal Swedish Academy of Sciences.

References (50)

  • S.L. Jones

    Noxious heat-evoked fos-like immunoreactivity in the rat lumbar dorsal horn is inhibited by glutamate microinjections in the upper cervical spinal cord

    Brain Res.

    (1998)
  • I. Kalezic et al.

    Distinctive pattern of c-fos expression in the feline cervico-lumbar spinal cord after stimulation of vanilloid receptors in dorsal neck muscles

    Neurosci. Lett.

    (2004)
  • V.M. King et al.

    Somatotopical organization of fos-like immunoreactivity in rat cervical spinal cord following noxious stimulation of the forelimb

    Neuroscience

    (2000)
  • V.A. Maisky et al.

    NADPH-diaphorase activity and c-fos expression in medullary neurons after fatiguing stimulation of hindlimb muscles in the rat

    Auton. Neurosci.: Basic Clin.

    (2002)
  • D. Menétrey et al.

    Propriospinal fibers reaching the lumbar enlargement in the rat

    Neurosci. Lett.

    (1985)
  • S. Mense et al.

    Spinal and supraspinal terminations of primary afferent fibers from the gastrocnemius-soleus muscle in the cat

    Neuroscience

    (1988)
  • S. Mense et al.

    Spinal termination of nociceptive afferent fibers from deep tissues in the cat

    Neurosci. Lett.

    (1986)
  • M.J. Millan

    Descending control of pain

    Prog. Neurobiol.

    (2002)
  • A.I. Pilyavskii et al.

    c-fos expression and NADPH-diaphorase reactivity in spinal neurons after fatiguing stimulation of hindlimb muscles in the rat

    Brain Res.

    (2001)
  • Z. Puskár et al.

    A population of large lamina I projection neurons with selective inhibitory input in rat spinal cord

    Neuroscience

    (2001)
  • T. Sakurada et al.

    Effect of spinal nitric oxide inhibition on capsaicin-induced nociceptive response

    Life Sci.

    (1996)
  • M. Schieppati et al.

    Neck muscle fatigue affects postural control in man

    Neuroscience

    (2003)
  • K.A. Sluka et al.

    Increased spinal release of excitatory amino acids following intradermal injection of capsaicin is reduced by a protein kinase G inhibitor

    Brain Res.

    (1998)
  • A.J. Todd et al.

    Some inhibitory neurons in the spinal cord develop c-fos-immunoreactivity after noxious stimulation

    Neuroscience

    (1994)
  • S.R. Vincent et al.

    Histochemical mapping of nitric oxide synthase in the rat brain

    Neuroscience

    (1992)
  • Cited by (18)

    • NADPH-diaphorase reactivity and Fos-immunoreactivity within the ventral horn of the lumbar spinal cord of cats submitted to acute muscle inflammation induced by injection of carrageenan

      2016, Acta Histochemica
      Citation Excerpt :

      In cats with chronic muscle inflammation, we have earlier recorded a marked decrease in NADPH-diaphorase activity within superficial laminae of the dorsal horn on the ipsilateral side of the L6/L7 segments (Steffens et al., 2007). However, the population of spinal NADPH-diaphorase reactive (NADPH-dr) neurons in the case of muscle pain are capable of providing a multidirectional response – an increase or a decrease in their number in the gray matter of the spinal cord (Hoheisel et al., 1997; Pilyavskii et al., 2005; Steffens et al., 2007). The main interest of many researches in case of pain development was focused on changes in the distribution patterns and mean number of NADPH-dr cells within the dorsal horn and area around central canal, which receive inputs from visceral and cutaneous noxious afferents (Freire et al., 2009).

    • Long lasting activity of nociceptive muscular afferents facilitates bilateral flexion reflex pattern in the feline spinal cord

      2015, Neuroscience Research
      Citation Excerpt :

      In this respect the behavioural hypersensitivity caused by CFA induced inflammation seems to be similar to neuropathic behavioural hypersensitivity (Raghavendra et al., 2004). The extensive bilateral induction of a high number of c-fos-immunoreactive cells throughout the lower lumbar and upper sacral spinal cord during CFA induced inflammation is in line with the widespread occurrence of a high expression of c-fos-immunoreactive neurones in the cervical and lumbar spinal cord after stimulation of vanilloid receptors in the dorsal neck muscles with capsaicin (Pilyavskii et al., 2005). As in the case of the current experiments those authors observed a particularly high expression of c-fos-immunoreactivity within the intermediate zone (VII), where last-order premotor interneurones as well as the cells of origin of segmental commissural interneurones and inter-segmental crossed and uncrossed descending propriospinal pathways are located (Jankowska et al., 2009).

    • 7-Nitroindazole enhances c-Fos expression in spinal neurons in rats realizing operant movements

      2014, Acta Histochemica
      Citation Excerpt :

      Excitatory and inhibitory dorsal and ventral horn interneurons relaying information from these afferents are the components of the complex networks involved in motor activity. In adult animals (rats and cats) the spinal interneurons, predominantly responsive to noxious stimulation, have been recorded in layer 1, in the outer part of the Substantia gelatinosa (layer 2o), and also in the lateral (reticular) part of layer 5 (Hunt et al., 1987; King and Apps, 2000; Buritova and Besson, 2002; Pilyavskii et al., 2005; Schomburg et al., 2007). Recently, we evaluated the patterns of c-Fos expression (a marker of neuronal activation) in the spinal cord of rats after long-lasting training and realization of operant reflexes (without using a NOS blocker in the study) (Vlasenko et al., 2011).

    • Immediate reduction in temporal sensory summation after thoracic spinal manipulation

      2011, Spine Journal
      Citation Excerpt :

      Furthermore, activation of capsacin-sensitive vanilloid receptors in cervical muscles of cats increases the neuronal activity of the cervical and lumbar dorsal horns [37,38]. This activation in the lumbar dorsal horn occurs bilaterally with the highest concentration of activity in Laminas I and V [37,38], representing areas with the largest concentration of nociceptive neurons receiving terminations from c-fiber afferents [41], which are hypothesized to be the primary inputs for TSS [25,42,43]. The implications for this caudal effect on TSS remain unclear.

    • Acute muscle inflammation enhances the monosynaptic reflexes and c-fos expression in the feline spinal cord

      2007, European Journal of Pain
      Citation Excerpt :

      In contrast, after fatiguing muscle stimulation the significant increase in the mean number of Fos-ir cell was found in the superficial laminae and neck of the dorsal horn (Pilyavskii et al., 2001). We have recently found that after intramuscular injections of capsaicin (that selectively influences the vanilloid receptors), the high number of Fos-ir neurons was also registered predominantly in the superficial laminae (Kalezic et al., 2004; Pilyavskii et al., 2005). The vigorous expansion of c-fos expression to the deeper laminae in carrageenan-treated animals may testify to the “second wave” of neuronal activation (Harris, 1998).

    View all citing articles on Scopus
    View full text