Elsevier

Neuroscience

Volume 186, 14 July 2011, Pages 201-207
Neuroscience

Pain Mechanisms and Sensory Neuroscience
Research Paper
Behavioral and immunohistochemical evidence for central antinociceptive activity of botulinum toxin A

https://doi.org/10.1016/j.neuroscience.2011.04.026Get rights and content

Abstract

Botulinum toxin A (BTX-A) is approved for treatment of different cholinergic hyperactivity disorders, and, recently, migraine headache. Although suggested to act only locally, novel observations demonstrated bilateral reduction of pain after unilateral toxin injection, and proposed retrograde axonal transport, presumably in sensory neurons. However, up to now, axonal transport of BTX-A from periphery to CNS was identified only in motoneurons, but with unknown significance. We assessed the effects of low doses of BTX-A injected into the rat whisker pad (3.5 U/kg) or into the sensory trigeminal ganglion (1 U/kg) on formalin-induced facial pain. Axonal transport was prevented by colchicine injection into the trigeminal ganglion (5 mM, 2 μl). To find the possible site of action of axonally transported BTX-A, we employed immunohistochemical labeling of BTX-A-truncated synaptosomal-associated protein 25 (SNAP-25) in medullary dorsal horn of trigeminal nucleus caudalis after toxin injection into the whisker pad. Both peripheral and intraganglionic BTX-A reduce phase II of formalin-induced pain. Antinociceptive effect of BTX-A was prevented completely by colchicine. BTX-A-truncated SNAP-25 in medullary dorsal horn (spinal trigeminal nucleus) was evident 3 days following the peripheral treatment, even with low dose applied (3.5 U/kg). Presented data provide the first evidence that axonal transport of BTX-A, obligatory for its antinociceptive effects, occurs via sensory neurons and is directed to sensory nociceptive nuclei in the CNS.

Graphical Abstract

Appearance of cleaved SNAP-25 in ipsilateral medullar dorsal horn (trigeminal nucleus caudalis) following botulinum toxin A (15 U/kg) injection into the whisker pad.

Highlights

▶Peripheral and intraganglionic BTX-A reduce formalin-induced facial pain. ▶Antinociceptive effect of BTX-A depends on axonal transport in trigeminal neurons. ▶After peripheral BTX-A application, cleaved SNAP-25 appears in medullary dorsal horn. ▶Central cleaved SNAP-25 appears with delay and at low peripheral BTX-A dose. ▶Antinociceptive effect of peripheral BTX-A is coupled with SNAP-25 cleavage in CNS.

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Section snippets

Animals

Male Wistar rats (University of Zagreb School of Medicine, Croatia), weighing 300–400 g, kept on 12 h/12 h light and dark cycle, were used in all experiments. The experiments were conducted according to the European Communities Council Directive (86/609/EEC) and recommendations of the International Association for the Study of Pain (Zimmerman, 1983). All efforts were made to reduce the number of animals used and to reduce their suffering. Animal procedures were approved by the Ethical Committee

BTX-A reduces formalin-induced orofacial pain: necessity of axonal transport in sensory neurons

BTX-A had no significant antinociceptive effects during phase I of formalin-induced pain. However, peripheral BTX-A pretreatment (3.5 U/kg) significantly reduced the time of facial grooming during phase II of formalin-induced pain (measured 3 days post BTX-A injection). Injection of colchicine (5 mM) into trigeminal ganglion abolished the effect of subsequently applied BTX-A (Fig. 2).

Intraganglionic BTX-A (1 U/kg) reduced the formalin-induced face grooming 2 days after the injection (Fig. 3).

Discussion

Cleavage of SNAP-25 at neuromuscular junctions or autonomic synapses, induced by enzymatic activity of BTX-A light chain, results in blockade of acetylcholine (ACh) release. Analogous mechanism was proposed as an explanation of antinociceptive activity in peripheral sensory neurons (Cui et al., 2004, Aoki, 2005). In formalin-induced inflammatory pain, peripheral BTX-A pretreatment had no effect on the acute nociceptive pain in phase I but it reduced pain during inflammatory phase II,

Conclusion

Antinociceptive effect of BTX-A requires axonal transport through sensory neurons and it is associated with occurrence of truncated SNAP-25 in central sensory nociceptive nuclei.

Acknowledgments

This work was supported by Croatian Ministry of Science, Education and Sport, (Project No. 108-1080003-0001) and Deutscher Academischer Austauch Dienst (DAAD)—project awarded to Professors Peter Riederer, Jürgen Deckert and Zdravko Lacković. Antibody to BTX-A–cleaved SNAP-25 was a kind gift from Assist. Prof. Ornella Rossetto (University of Padua, Italy). We wish to thank Dr. Matteo Caleo (Institute of Neuroscience, Pisa, Italy) for advices regarding the immunohistochemistry protocol as well as

References (30)

  • P. Raboisson et al.

    The orofacial formalin test

    Neurosci Biobehav Rev

    (2004)
  • M. Alexiades-Armenakas

    Retrograde transport and transcytosis of botulinum toxin serotypes to the brain: analysis of potential neurotoxicity

    J Drugs Dermatol

    (2008)
  • F. Antonucci et al.

    Long-distance retrograde effects of botulinum neurotoxin A

    J Neurosci

    (2008)
  • S.K. Aurora et al.

    Botulinum toxin type A prophylactic treatment of episodic migraine: a randomized, double blind, placebo-controlled exploratory study

    Headache

    (2007)
  • L. Bach-Rojecky et al.

    Lack of anti-inflammatory effects of botulinum toxin A in experimental models of inflammation

    Fundam Clin Pharmacol

    (2008)
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