Effects of l-threo-DOPS, an l-noradrenaline precursor, on locus coeruleus-originating neurons in spinal trigeminal nucleus

Abstract Electrophysiological studies using reserpinized cats were performed to examine the effects of l - threo -3,4-dihydroxyphenylserine( l -threo-DOPS) on the noradrenergic pathway from the locus coeruleus (LC)_to the spinal trigeminal nucleus (STN). The spike generation of STN relay neurons induced by trigeminal nerve stimulation was not affected by LC conditioning stimulation nor iontophoretic application of l - threo -DOPS. After intraventricular administrayion of l - threo -DOPS, the inhibition of the spike generation was seen with LC conditioning stimulation and blocked by iontophoretically applied sotalol, suggesting that l -noradrenaline converted from l - threo -DOPS inhibits transmission of STN relay neurons.