Abstract
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 MG motoneurons fired with doublets during the FS bursting activity, motoneuron membrane potential from some posterior biceps (PB) motoneurons exhibits a depolarization in relation to the PB (ENG). It changed to a locomotor drive potential in relation to one of the double ENG, PB bursts. In FDL and semitendinosus (ST) motoneurons, the membrane potential was depolarized during FS, but it did not change during FL. Glutamic acid injected in the L3‐L4 spinal cord segment favored the transition from FS to FL. During FL, glutamic acid produces a duration increase of extensors ENGs. Serotonin increases the ENG amplitude in extensor motoneurons, as well as the duration of scratching episodes. It did not change the SC duration. Segregation and motoneurons excitability could be regulated by the rhythmic generator and the pattern generator of the central pattern generator.
Highlights
The episodes of real or fictive locomotion occurring in precolicular decerebrated cats (Bayev 1978; Perret and Cabelguen 1980) are initiated by the locomotor regions of the brainstem (Orlovsky 1972; Mori et al 1978; GarciaRill et al 1985; Ryczko and Dubuc 2013), by the mesencephalic locomotor region (MLR) activating via segmental spinal interneurons liberating excitatory amino acids (Douglas et al 1993)
Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society
In immobilized brain cortex-ablated cats (BCAC), we found episodes of fictive scratching (FS) and fictive locomotion (FL) by pinna stimulation
Summary
The episodes of real or fictive locomotion occurring in precolicular decerebrated cats (Bayev 1978; Perret and Cabelguen 1980) are initiated by the locomotor regions of the brainstem (Orlovsky 1972; Mori et al 1978; GarciaRill et al 1985; Ryczko and Dubuc 2013), by the mesencephalic locomotor region (MLR) activating via segmental spinal interneurons liberating excitatory amino acids (Douglas et al 1993). Duenas-Jimenez et al. The spinal cord CPG for locomotion seems to be constituted by neural elements placed on two levels: one producing the rhythm for FL or FS and the other producing several motor patterns in a hind limb extensor and flexor motoneurons (McCrea and Rybak 2007). In immobilized BCAC, the serotonin or glutamic acid effects when injected in the L3-L4 spinal cord level are not known This issue was studied since pinna stimulation could generate FS or FL using different neurotransmitters modifying the rhythm generator or the patterns generator forming the spinal CPG (Lafreniere-Roula and McCrea 2005). Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society
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