EFFECTS OF EXPOSURE TO BOTULINUM TOXIN TYPE A DURING PREGNANCY: EVALUATION OF LOCOMOTOR ACTIVITY, RELATIVE ORGAN WEIGHT, AND ENZYMATIC ASSAY

Botulinum toxin type A (BT-A) is a neurotoxin capable of inducing paralysis and muscle atrophy; however, at low doses, it’s used in the treatment of neuromuscular disorders. However, there’s a lack of studies addressing its safety and effects during critical periods of human development, such as pregnancy, which contraindicates its use during this period. This study aimed to evaluate locomotor activity, relative muscle weight, and plasma cholinesterase activity in Wistar rats exposed to BT-A during gestation. Adult pregnant rats received a single intramuscular dose of BT-A (4, 8, or 16 U/kg) or saline solution (0.9% NaCl) on gestational day (GD) 5 (n=8 animals/group). Behavioral assessments included the open field and gait tests, performed on GD6 and lactation day (LD) 19 to investigate both short- and long-term effects. The soleus and gastrocnemius muscles were collected to determine relative muscle weight, and blood samples were obtained to measure plasma cholinesterase activity. No alterations were observed in any parameter evaluated in the open field test. However, changes in gait pattern were detected, including step length and extension of the right toes and foot, along with a reduction in the weight of the right muscles, corresponding to the limb selected for BT-A administration. These findings were expected and are consistent with the localized paralysis and muscle atrophy induced by the toxin. No differences were observed in plasma cholinesterase activity, indicating that BT-A effects were restricted to the application site and did not produce systemic toxicity, suggesting a limited and safe distribution profile.