Mechanisms of oscillation and sensory processing in the rat somatosensory cortex-In vivo patch-clamp analysis-

Abstract

Recent imaging techniques, including PET and fMRI have provided basic evidence concerning functional locations. However, those techniques are not suitable for analyzing how sensory information is processed at the cortex. To examine a mechanism of the pain processing, in vivo patch-clamp recordings were made from cortex neurons and analyzed synaptic responses evoked by stimulation. After anesthesia, a rat was placed in a stereotaxic apparatus. After opening of dura and pia mater, recording electrodes were inserted through the hole. All cortex neurons exhibited an oscillatory activity at frequency of 0.5 to 5 Hz under urethane anesthesia. The oscillation was well correlated with EEG and was reduced by injection of benzodiazepine systemically. To clarify a site of origin of oscillation, a GABAA receptor agonist, muscimol was injected to thalamus. Muscimol reduced the oscillatory acitivities together with the EEG frequency, indicating that the GABAergic system in the thalamus plays an critical role in the generation of oscillation. Non-noxious stimulation elicited a barrage of EPSCs. In contrast, noxious pinch stimuli did not evoke any significant responses in all neurons tested. Because excitation of cortex neurons by noxious stimuli has been shown extracellularly, no noxious response in the present study may be due to recording from different population. [Jpn J Physiol 55 Suppl:S22 (2005)]