title: Selective inhibition by methysergide of the monosynaptic reflex discharge in the isolated spinal cord of the newborn rat.
abstract: In the isolated spinal cord of the newborn rat, methysergide and LSD-25 depressed the monosynaptic reflex discharge selectively. Cyproheptadine and dimethothiazine did not inhibit the monosynaptic reflex. The selective inhibitory effect of methysergide on the monosynaptic reflex was not due to a presumptive low safety factor of this reflex. The inhibition was restored under a condition such as the compound action potential in the dorsal root was enhanced by 4-aminopyridine. Methysergide did not decrease the sensitivity of the motoneuron to substance P and L-glutamic acid. It is suggested that methysergide acts at the presynaptic terminal of Ia afferent fibers and depresses evoked transmitter release.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000831:Animals, Newborn; D004553:Electric Conductivity; D005260:Female; D008297:Male; D008784:Methysergide / Q000494:pharmacology*; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology; D051381:Rats; D012018:Reflex / Q000187:drug effects*; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*; D013569:Synapses / Q000187:drug effects / Q000502:physiology*
chemical_list: D008784:Methysergide