Effects of selective spinal cord lesions on the spinal motor evoked potential (MEP) in the rat

Conduction pathways of motor evoked potentials following transcranial magnetic stimulation: A rodent study using a ?Figure-8? coil

“…It is unclear why sMEPs were not completely abolished after transection of the ventral funiculus. This might be due to incomplete transection or to the participation of the gray matter function that descends and ascends in the cord to influence the anterior horn cell pool, such as the propriospinal system function described by Adamson et al 1 for the generation of rat MEPs. The contribution of the corticospinal tract to motor function has not been well understood in rats.…”

“…7,14 Because the origins and conduction pathways of magnetic MEPs in the rat may differ from those in other animals, in the rat we further compared magnetic MEPs with MEPs obtained following monopolar or bipolar electric stimulation in the same way as in previous studies. 9,22,25,29 According to Zappulla et al 1,29 and Fujiki et al, 9 monopolar electric MEPs in rats originate from the subcortical and brain stem structures and conduct activity from the ventral and lateral funiculi in the spinal cord, reflecting extrapyramidal system function. Their technique of putting the cathode in the submucosa of the hard palate may make it easy to obtain extrapyramidal excitation.…”

“…1,9,22,25,29 For monopolar electric stimulation, a 0.8-mm silver ball electrode (Unique Medical, Kyushu, Japan) was set on the pial surface as the anode, and a needle electrode was inserted into the submucosa of the hard palate as the cathode. Bipolar electric stimulation was delivered between 2 stainless steel electrodes (Unique Medical), 0.25 mm in diameter and 1 mm apart, being the anode set laterally.…”

Acute transplantation of olfactory ensheathing cells or Schwann cells promotes recovery after spinal cord injury in the rat

“…Supramaximal transcranial stimulation produces depolarization of cortical and brainstem motor neurons, which propagate the impulse along the spinal cord to synapse and depolarize lumbar motoneurons (Konrad et al, 1990). Injuries of the spinal cord compromise the preservation of MEPs, mainly when the lateral funiculi are lesioned (Adamson et al, 1989). The maintenance of MEPs in OECand SC-grafted groups is thus attributable to the greater sparing of the lateral funiculi in these animals compared with DM animals.…”

Olfactory ensheathing cells transplanted in lesioned spinal cord prevent loss of spinal cord parenchyma and promote functional recovery

“…Motor-evoked potentials (MEPs) were recorded using monopolar needle electrodes placed at the tibialis anterior muscle, while the contralateral sensorimotor cortex was stimulated by single rectangular pulses of 0.1-ms duration, delivered through needle electrodes inserted subcutaneously, the cathode over the skull overlying the sensorimotor cortex and the anode at the nose. This configuration produces transcranial stimulation that activates subcortical efferent pathways (Zappulla et al 1988;Adamson et al 1989). For somatosensory-evoked potentials (SSEPs), electrical stimuli 0.1 ms in duration and 4 mA in intensity were applied at 5 Hz to the tibial nerve by means of two needle electrodes inserted at the ankle.…”