In vivo patch-clamp recording of synaptic activities in somatosensory cortex in rats

Abstract

All animal care was performed in accordance with the University guidelines. The rodent primary somatosensory cortex (SI) contains a detailed representation of the whiskers on the face. The sensory information is transferred to SI from whiskers via the ventroposteromedial nucleus (VPM) of the thalamus. To investigate detailed synaptic activities of cortical neurons receiving input from thalamus, we have applied the in vivo whole-cell patch-clamp technique to rat SI. Male SD rats were anesthetized with urethane. Recording pipettes were filled with standard solution containing 0.2% neurobiotin. Rats were then perfused for the morphological studies. Most recorded neurons exhibited spontaneous EPSCs (V_H=-70mV) and spontaneous IPSCs (V_H=0mV). Deflection of contralateral whiskers elicited increased EPSCs in both frequency and amplitude. Some neurons exhibited membrane current fluctuation (oscillation). Application of CNQX through the perfusion line abolished the oscillatory current, indicating that the oscillation consisted of the summated EPSCs. Whisker stimulation distorted the regularity of the oscillation indicating that oscillation could be related to neural processing in stationary phase. A single electrical stimulation on VPM by using bipolar electrode induced an EPSC with short latency (2ms) as well as EPSCs with long latency (120ms) in cortical neurons and this stimulation also suppressed the oscillation suggesting that thalamic activities could regulate the oscillation. [Jpn J Physiol 54 Suppl:S145 (2004)]