Effects of Intravenous anesthetics on Phosphatidylinositol Response of Spinal Descending Inhibitory Pathways of Rat

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Noradrenergic neurons arise from the locus coeruleus and project widely to the spinal cord, cerebral cortex andothers. Noradrenergic pathways in the spinal cord are considered to be one of the central descending inhibitory influences on spinal sensory transmission. Norepinephrine (NE) in the central nervous system has the effect to stimulate phosphatidylinositol (PI) response through aradrenergic receptors. The present study was designed to examine the effects of intravenous anesthetics on NE-induced PI response of rat spinal cords. Materials and Methods: Male Wistar ratsweighing 250-350 g were used for the experiments. , The rats were anesthetized with pentobarbital and their thoracic spinal cord was rapidly isolated. The spinal cord waschopped into 1-mm-wide slices. Three pieces of the slice were placed in small flat-bottomed tubes andincubated in K-H solution containing 5 mM LiCI. The effects of intravenous anesthetics on NE-induced inositol monophosphate (IP_1) accumulation were examined. We measured [^3H]IP_1 in spinal cord slices incubated with [^3H]myo-inositol with aliquid scintillation counter. Results : NE-induced IP_1 accumulation of spinal cord slices was attenuated dose-dependently by droperidol, but was not attenuated by ketamine, fentanyl and midazolam.