Abstract
Spinal actions of intravenous anesthetics such as propofol are less clear. The aim of this study was to investigate the spinal effects of propofol on nociceptive transmission. Adult male rats were used in this study. For in vitro patch-clamp study, a transverse slice of the spinal cord was cut and blind whole-cell patch-clamp recordings were made from substantia gelatinosa (SG) neurons. The half decay time of GABAergic evoked inhibitory postsynaptic currents (eIPSCs) was increased by bath-applied propofol dose dependently. Furthermore, for in vivo patch-clamp study, a rat was fixed in a stereotaxic apparatus after the lumbar spinal cord was exposed under urethane anesthesia. Propofol was systemically injected from left femoral vein, and its effect was evaluated before and after injection of 5 mg/kg propofol under the voltage-clamp mode. Propofol reversibly prolonged decay time of GABAergic spontaneous IPSC in all neurons tested. In the current clamp mode, pinch stimuli applied to the hindlimb elicited a barrage of excitatory postsynaptic potentials, some of which initiated an action potential (AP). Number of APs decreased after injection of propofol in most of neurons tested. These results suggest that systemically bolus injected propofol in clinical dosage reversibly depress noxious transmission at least in part by enhancing postsynaptic GABA receptors in the SG of the spinal cord. [J Physiol Sci. 2006;56 Suppl:S180]
