Inhibition of motoneurons during the cutaneous silent period in the spinal cord of the turtle

Abstract

The transient suppression of motor activity in the spinal cord after a cutaneous stimulus is termed the cutaneous silent period (CSP). It is not known if CSP is due to suppression of the premotor network or direct inhibition of motoneurons. This issue was examined by intracellular recordings from motoneurons in the isolated carapace-spinal cord preparation from adult turtles during rhythmic scratch-like reflex. Electrical stimulation of cutaneous nerves induced CSP-like suppression of motor nerve firing during rhythmic network activity. The stimulus that generated the CSP-like suppression of motor activity evokes a polysynaptic compound synaptic potential in motoneurons and suppressed their firing. This compound synaptic potential was hyperpolarizing near threshold for action potentials and was associated with a substantial increase in conductance during the CSP in the motor pool. These results show that direct postsynaptic inhibition of motoneurons contributes to the CSP.

Spinal excitability changes do not influence the mechanisms of split‐hand syndrome in amyotrophic lateral sclerosis

“…22 Results of some investigators favor a postsynaptic inhibition of motor neurons mediated through spinal interneurons. 23,24 Similarly to the findings of Gilio et al, 25 the CutSP latencies were markedly prolonged in our ALS group. Such a prolongation of CutSP latencies has been reported in stroke 25 and cervical spondylotic myelopathy.…”

“…Whether the inhibition occurs at the presynaptic or postsynaptic levels is still under debate . Results of some investigators favor a postsynaptic inhibition of motor neurons mediated through spinal interneurons . Similarly to the findings of Gilio et al ., the CutSP latencies were markedly prolonged in our ALS group.…”

Increased activity of pre‐motor network does not change the excitability of motoneurons during protracted scratch initiation

“…To control the applied stimuli better we adopted electrical stimulation of appropriate cutaneous nerves to evoke fictive scratch (Currie & Stein, 1988; Guzulaitis et al 2012). The induction of scratch activity during a train of electrical stimuli depends on both stimulus intensity (Fig.…”

“…Electrical stimuli for induction of scratch episodes were applied to a cut ipsilateral cutaneous nerve (Currie & Stein, 1988; Guzulaitis et al 2012) using a suction electrode.…”