Novel evidence suggests that the antinociceptive effect of botulinum toxin type A (BT-A) is of central origin. In this doctoral thesis, we verified this assumption in previously insufficiently investigated types of pain, investigated the interaction with central neurotransmitters as the possible mechanism of action and tried to determine the site of the toxin’s action within the central nervous system (CNS). Male Wistar rats were used in experiments. We examined the effect of selective and nonselective opioid and GABAA antagonists, applied systemically, spinally and supraspinally, on antinociceptive effect of peripherally (subcutaneously into hind paw) applied BT-A in inflammatory, neuropathic, and bilateral pain. Neuronal and glial cells’ activation, proinflammatory cytokines’ and μ-opioid receptors mRNA expression, and Leu/Met-enkephalin protein expression were analyzed using immunofluorescence and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) in lumbar spinal cord tissue. Further, we investigated the antinociceptive effect of BT-A following peripheral, spinal and supraspinal application. In parallel, enzymatic activity of BT-A in CNS tissue was examined using immunofluorescence. Opioid and GABAA antagonists, applied systemically and intrathecally, dose-dependently abolished the antinociceptive effect of peripheral BT-A in all tested models, while no effect was observed following their supraspinal application. The effect of antagonists was short-lasting. BT-A reduced neuronal activation in dorsal horn, which was abolished by both, opioid and GABAA antagonist. BT-A diminished pain in, yet uninvestigated, models of visceral pain (peritonitis and colitis). BT-A’s bilateral antinociceptive action occurs after toxin’s presence on ipsilateral side only. BT-A reduced pain after peripheral and intrathecal application, but not after application in cisterna magna or cerebral ventricles, despite of its enzymatic activity in brain regions involved in nociception. BT-A has segmental antinociceptive effect at the spinal level, which involves an indirect activation of endogenous opioid and GABA-ergic systems. These findings might guide clinical investigations of potentially useful additive or synergistic effects with conventional analgesics and direct clinical trials for novel indications and the routes of application, like intrathecal.