Unilateral whisker pad injection of botulinum toxin type a enhances spatial learning in mice

Neuroreport. 2018 Aug 15;29(12):987-992. doi: 10.1097/WNR.0000000000001035.

Abstract

The central cholinergic nervous system plays an important role in cognition, with acetylcholine hypofunction considered to be a major factor of dementia. Botulinum toxin type A (BoNT/A), a potent poison secreted by Clostridium botulinum, is used widely for dystonia treatment and facial cosmesis. BoNT/A injection inhibits acetylcholine release in the neuromuscular junction through cleavage of synaptosomal-associated protein of 25 kDa in cholinergic terminals. Furthermore, beyond the injection site, BoNT/A undergoes retrograde transport and transcytosis to the central nervous system from peripheral cholinergic terminals. However, whether peripheral BoNT/A injection affects the function of the central nervous system and induces learning deficits remains unclear. We injected mice with different doses of BoNT/A (2, 10, and 50 U/kg) or sterile saline (control) into the left whisker pad to test spatial learning performance at different times after injection using the Morris water maze. At 3 days and 4 weeks after injection, the spatial learning ability of the control and BoNT/A-treated mice showed no significant differences. Surprisingly, however, rather than spatial learning impairment at 6 weeks after injection, BoNT/A-treated mice spent less time than control mice in locating the experimental platform, indicating that BoNT/A facial injection might promote spatial learning. Furthermore, our study suggests that facial application of BoNT/A is safe and could play a positive role in ameliorating the spatial learning deficits associated with neurodegenerative diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Botulinum Toxins, Type A / administration & dosage*
  • Male
  • Maze Learning / drug effects
  • Maze Learning / physiology
  • Mice
  • Mice, Inbred C57BL
  • Neuromuscular Agents / administration & dosage*
  • Spatial Learning / drug effects*
  • Spatial Learning / physiology
  • Vibrissae / drug effects*
  • Vibrissae / innervation
  • Vibrissae / physiology

Substances

  • Neuromuscular Agents
  • Botulinum Toxins, Type A