Recording of motor and somatosensory evoked potential in an anaesthetised Wistar rat using digital polyrite system

Objectives: The aim of this article is to explain the detailed methodology to record Motor evoked potential (MEP) and somatosensory evoked potential (SSEP) in adult albino Wistar rat, male (200–250 g) which has not been defined previously. Materials and Methods: We have standardised recording of both MEP and SSEP in these rats under anaesthesia on ADI digital polyrite system. Results: Evoked potentials have been widely studied in spinal cord injured patients to estimate the degree of injury and to establish a predictive measure of functional recovery. MEPs and SSEPs, arising from the motor cortex or peripheral nerve and generated either by direct electrical stimulation or by transcranial magnetic stimulation, have been advocated as a reliable indicator of descending and ascending pathway integrity. In the rat brain, there is a physical overlap between the motor and somatosensory cortex. Hence, our objective was to identify the exact area for stimulation in the cortex where we could record maximum response with the application of minimum electrical stimulation. Conclusion: The recording of MEP and SSEP together provides a powerful neurological technique to monitor the tracts of the spinal cord.

Role of Pre-Synaptic NMDA Receptors in the Modulation of Inhibitory Synaptic Transmission in Sensory-Motor and Visual Cortical Pyramidal Neurons in Brain Slices of Young Epileptic Mice

Background: Previous studies from animal models have shown that pre-synapticNMDA receptors (preNMDARs) are present in the cortex, but the role of inhibition mediated bypreNMDARs during epileptogenesis remains unclear. In this study, we wanted to observe thechanges in GABAergic inhibition through preNMDARs in sensory-motor and visual corticalpyramidal neurons after pilocarpine-induced status epilepticus.Methods: Using a pilocarpine-induced epileptic mouse model, sensory-motor and visualcortical slices were prepared, and the whole-cell patch clamp technique was used to recordspontaneous inhibitory post-synaptic currents (sIPSCs).Results: The primary finding was that the mean amplitude of sIPSC from the sensorymotorcortex increased significantly in epileptic mice when the recording pipette contained MK-801 compared to control mice, whereas the mean sIPSC frequency was not significantly different,indicating that post-synaptic mechanisms are involved. However, there was no significant presynapticinhibition through preNMDARs in the acute brain slices from pilocarpine-inducedepileptic mice.Conclusion: In the acute case of epilepsy, a compensatory mechanism of post-synapticinhibition, possibly from ambient GABA, was observed through changes in the amplitude withoutsignificant changes in the frequency of sIPSC compared to control mice. The role of preNMDARmediatedinhibition in epileptogenesis during the chronic condition or in the juvenile stagewarrants further investigation.