title: Spinal botulinum neurotoxin B: effects on afferent transmitter release and nociceptive processing.
abstract: Botulinum neurotoxin B (BoNT-B) mediates proteolytic cleavage of VAMP I/II (synaptobrevins I/II), which prevents vesicle-membrane fusion and blocks neurotransmitter release. In the present study, we investigated the effects of BoNT-B on neurotransmitter release in vivo from spinal primary afferent sensory fibers and the effects of this blockade on nociception. With intrathecally (IT) delivered BoNT-B in C57B/l6 mice, we characterized the effects of such block on the release of substance P (SP) from spinal afferent nociceptors (as measured by neurokinin-1 receptor, NK1-R, internalization), spinal neuronal activation (as indicated by spinal C-Fos expression) and nociceptive behavior after intraplantar (IPLT) formalin. In addition, we investigated the effect of IT BoNT-B on spinal nerve ligation-induced tactile allodynia. A single percutaneous IT injection of BoNT-B 0.5 U at 2 or 5 days prior to IPLT formalin reduced NK1-R internalization and C-Fos expression. These effects correlated with BoNT-B cleavage of VAMPI/II protein in tissue lysate. IT BoNT-B also produced a corresponding reduction in phase 2 of formalin-evoked flinching behavior for over 30 days after IT injection. In mice with spinal nerve ligation (SNL), tactile allodynia was observed, which was attenuated by IT BoNT-B 0.5 U over the next 15 days, as compared to vehicle animals. These effects were observed without effects upon motor function. The specificity of the IT BoNT-B effect is indicated by: i) IT co-injection of BoNT-B and anti-BoNTB antibody prevented effects on SP release, and ii) IT BoNT-B 50 U in the Sprague Dawley rats showed no effect on formalin-evoked flinching or SNL-induced tactile allodynia, which is consistent with rat resistance to BoNT-B. IT BoNT-B blocks transmitter release from spinal primary afferents, and attenuates inflammatory nociceptive response and spinal nerve injury-induced neuropathic pain, in the absence of motor impairment. These observations provide an initial assessment of the ability of IT BoNT-B to regulate spinal nociceptive processing.
authors.affiliation: Department of Biological Sciences, University of California San Diego, La Jolla, California, United States of America.
authors.forename: Polly P
authors.initials: PP
authors.lastname: Huang
authors.forename: Imran
authors.initials: I
authors.lastname: Khan
authors.forename: Mohammed S A
authors.initials: MS
authors.lastname: Suhail
authors.forename: Shelle
authors.initials: S
authors.lastname: Malkmus
authors.forename: Tony L
authors.initials: TL
authors.lastname: Yaksh
mesh_terms: D000818:Animals; D001905:Botulinum Toxins / Q000378:metabolism*; D019274:Botulinum Toxins, Type A; D006930:Hyperalgesia / Q000188:drug therapy / Q000473:pathology*; D007150:Immunohistochemistry / Q000379:methods; D007278:Injections, Spinal; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D009437:Neuralgia; D009474:Neurons / Q000378:metabolism; D009475:Neurons, Afferent / Q000187:drug effects / Q000378:metabolism*; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000473:pathology; D013127:Spinal Nerves / Q000187:drug effects / Q000473:pathology*
chemical_list: C096323:rimabotulinumtoxinB; D001905:Botulinum Toxins; D019274:Botulinum Toxins, Type A