Facilitation of spinal motoneurone excitability by 5-hydroxytryptamine and noradrenaline.
The effects of iontophoretic application of 5-hydroxytryptamine (5-HT) and noradrenaline (NA) on lumbar motoneurone excitability were examined. 5-HT and NA produced long-lasting changes in motoneurone excitability as revealed by decreased threshold for glutamate-evoked motoneurone action potentials, increased rate of motoneurone firing evoked by suprathreshold amounts of glutamate and increased amplitude of ventral root and dorsal root evoked motoneurone field potentials. Neither 5-HT nor NA directly evoked motoneurone action potentials in the absence of other excitatory input. The 5-HT antagonist, methergoline, reduced glutamate-evoked motoneurone activity and prevented 5-HT, but not NA, facilitation of glutamate-evoked activity. These results suggest that 5-HT and NA enhance the effects of excitatory inputs to spinal motoneurones by actions on separate receptors.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004553:Electric Conductivity; D005071:Evoked Potentials / Q000187:drug effects; D005971:Glutamates / Q000494:pharmacology; D008297:Male; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology*; D051381:Rats; D012701:Serotonin / Q000494:pharmacology*; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*
D005971:Glutamates; D012701:Serotonin; D009638:Norepinephrine