Capsaicin-induced effects on c-fos expression and NADPH-diaphorase activity in the feline spinal cord
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)
- et al.
Effects of nefopam on the spinal nociceptive processes: a c-Fos protein study in the rat
Eur. J. Pharmacol.
(2002) Vanilloid receptors take a TRP beyond the sensory afferent
Pain
(2003)- et al.
Fatigue-induced changes in group IV muscle afferent activity: differences between high- and low-frequency electrically induced fatigues
Brain Res.
(1997) - et al.
Nitric oxidesynthase immunoreactivity in the rat, mouse, cat, and squirrel monkey spinal cord
Neuroscience
(1993) - et al.
Effects of neck extensor muscles fatigue on balance
Clin. Biomech.
(2004) - et al.
Capsaicin-induced central facilitation of a nociceptive flexion reflex in humans
Neurosci. Lett.
(1993) Using c-fos as a neural marker of pain
Brain Res. Bull.
(1998)- et al.
Inducible and constitutive transcription factors in the mammalian nervous system: control of gene expression by Jun, Fos and Krox, and CREB/ATF proteins
Brain Res. Brain Res. Rev.
(1998) - et al.
Expression of nitric oxide synthase and colocalization with Jun, Fos and Krox transcription factors in spinal cord neurons following noxious stimulation of the rat hindpaw
Brain Res. Mol. Brain Res.
(1994) - et al.
Walking evokes a distinctive pattern of Fos-like immunoreactivity in the caudal brainstem and spinal cord of the rat
Neuroscience
(1994)
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.
Distinctive pattern of c-fos expression in the feline cervico-lumbar spinal cord after stimulation of vanilloid receptors in dorsal neck muscles
Neurosci. Lett.
Somatotopical organization of fos-like immunoreactivity in rat cervical spinal cord following noxious stimulation of the forelimb
Neuroscience
NADPH-diaphorase activity and c-fos expression in medullary neurons after fatiguing stimulation of hindlimb muscles in the rat
Auton. Neurosci.: Basic Clin.
Propriospinal fibers reaching the lumbar enlargement in the rat
Neurosci. Lett.
Spinal and supraspinal terminations of primary afferent fibers from the gastrocnemius-soleus muscle in the cat
Neuroscience
Spinal termination of nociceptive afferent fibers from deep tissues in the cat
Neurosci. Lett.
Descending control of pain
Prog. Neurobiol.
c-fos expression and NADPH-diaphorase reactivity in spinal neurons after fatiguing stimulation of hindlimb muscles in the rat
Brain Res.
A population of large lamina I projection neurons with selective inhibitory input in rat spinal cord
Neuroscience
Effect of spinal nitric oxide inhibition on capsaicin-induced nociceptive response
Life Sci.
Neck muscle fatigue affects postural control in man
Neuroscience
Increased spinal release of excitatory amino acids following intradermal injection of capsaicin is reduced by a protein kinase G inhibitor
Brain Res.
Some inhibitory neurons in the spinal cord develop c-fos-immunoreactivity after noxious stimulation
Neuroscience
Histochemical mapping of nitric oxide synthase in the rat brain
Neuroscience
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 HistochemicaCitation 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 ResearchCitation 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 HistochemicaCitation 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 JournalCitation 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.
Neuroanatomical pathway of nociception originating in a low back muscle (multifidus) in the rat
2007, Neuroscience LettersAcute muscle inflammation enhances the monosynaptic reflexes and c-fos expression in the feline spinal cord
2007, European Journal of PainCitation 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).