Botulinum toxin type A (BoNT-A) is a neurotoxin synthesised by the bacterium Clostridium botulinum. Its specific mechanism of action, which involves proteolytic cleavage of SNAP-25, a protein responsible for exocytosis of various neurotransmitters, was recognized as a possible pharmacological solution for some autonomic disorders, conditions accompanied by muscle hypercontractility and certain types of pain. Antinociceptive effect of BoNT-A was long considered to be the consequence of solely peripheral inhibition of neurotransmitter exocytosis, but nowadays it is believed that more complex and still unresolved mechanisms are at play. The aim of this study was to investigate the possibility of transcytosis as a mechanism underlying the complex central action of BoNT-A on pain. BoNT-A (7 IU/kg) was unilaterally administered in the facial vibrissae of Wistar rats a day before the injection of antibody against BoNT-A (5 IU/10μL) inside the cisterna magna. After seven days, pain was caused by formalin application (2.5%) and the frequency of pain-associated behaviours was measured at 5-minute intervals over a period of 45 minutes. Peripherally applied BoNT-A reduced pain during the second phase of formalin test, corresponding to early inflammatory pain. Anti-BoNT-A prevented antinociceptive effect of BoNT-A, proposing central effects, mediated by transcytosis. Since the application of colchicine, an axonal transport blocker, in the contralateral trigeminal ganglion did not affect the antinociceptive effect of BoNT-A, possibility of peripheral diffusion of toxin and systemic spread to the contralateral side was excluded. Additionally, when BT-A was applied on the opposite side of the pain induction site, an antinociceptive effect was observed during the inflammatory phase of the formalin test, indicating that the contralateral effect of BT-A on pain is independent of the site of injury and the action of toxin on the site of application. In conclusion, the results presented in this master’s thesis contribute to the elucidation of the complex central action of BoNT-A on pain. For the first time, transcytosis in the sensory system is proposed as an important factor in the antinociceptive effect of BT-A, which requires further detailed investigation.