Efectos de la neurotoxina botulíníca tipo A sobre las características de disparo de motoneuronas oculomotoras en el gato despierto

Resumo

Botulinum neurotoxin type A is a presynaptic blocker of acetylcholine release in the peripheral nervous system. The effects of botulinum neurotoxin-injection into the lateral rectus muscle on the discharge pattern of abducens motoneurons were examined with the purpose of studying its possible action at a central level. During the first week post-injection, noticeable changes were found in the discharge pattern of abducens motoneurons resembling those found after axotomy. Nonetheless, from the second week postinjection onwards, the discharge characteristics of abducens motoneurons were markedly different from the axotomy effects. Thus, motoneurons fired a tonic basal rate that was almost unmodulated for saccades and ocular fixations. It is suggested that these changes are due to a direct effect of botulinum neurotoxin on the motoneuron itself and/or its synaptic inputs and not, or not only, due to the functional synaptic disconnection with its target muscle.