Hind limb motoneurons activity during fictive locomotion or scratching induced by pinna stimulation serotonin or glutamic acid in brain cortex‐ablated cats

摘要

In brain cortex‐ablated cats (BCAC), hind limb motoneurons activity patterns were studied during fictive locomotion (FL) or fictive scratching (FS) induced by pinna stimulation. In order to study motoneurons excitability: heteronymous monosynaptic reflex (HeMR), intracellular recording, and individual Ia afferent fiber antidromic activity (AA) were analyzed. The intraspinal cord microinjections of serotonin or glutamic acid effects were made to study their influence in FL or FS. During FS, HeMR amplitude in extensor and bifunctional motoneurons increased prior to or during the respective electroneurogram (ENG). In soleus (SOL) motoneurons were reduced during the scratch cycle (SC). AA in medial gastrocnemius (MG) Ia afferent individual fibers of L6‐L7 dorsal roots did not occur during FS. Flexor digitorum longus (FDL) and style="fixed-case">MG motoneurons fired with doublets during the style="fixed-case">FS bursting activity, motoneuron membrane potential from some posterior biceps ( style="fixed-case">PB) motoneurons exhibits a depolarization in relation to the style="fixed-case">PB ( style="fixed-case">ENG). It changed to a locomotor drive potential in relation to one of the double style="fixed-case">ENG, style="fixed-case"> PB bursts. In style="fixed-case">FDL and semitendinosus ( style="fixed-case">ST) motoneurons, the membrane potential was depolarized during style="fixed-case">FS, but it did not change during style="fixed-case">FL. Glutamic acid injected in the L3‐L4 spinal cord segment favored the transition from style="fixed-case">FS to style="fixed-case">FL. During style="fixed-case">FL, glutamic acid produces a duration increase of extensors style="fixed-case">ENGs. Serotonin increases the style="fixed-case">ENG amplitude in extensor motoneurons, as well as the duration of scratching episodes. It did not change the style="fixed-case">SC duration. Segregation and motoneurons excitability could be regulated by the rhythmic generator and the pattern generator of the central pattern generator.