Glucocorticoid enhancement of serotonergic facilitation of cat spinal monosynaptic motor neuron excitation

Intensive pretreatment with triamcinoline diacetate (8 mg/kg, i.m. once daily for 7 days) was found in the acute spinal (decerebrate) cat to potentiate the increase in monosynaptic spinal reflex transmission caused by coadministration of the serotonin precursor, d, l-5-hydroxytryptophan, and amitriptyline, a selective serotonin reuptake inhibitor. In addition, the ability of methysergide, a selective serotonin receptor antagonist, to reverse the monosynaptic excitatory actions of d, l-5-hydroxytryptophan plus amitriptyline was significantly reduced. This apparent glucocorticoid enhancement of the actions of a serotonergic spinal system that is facilitatory to motor neuron excitation may have relevance to the therapy of degenerative motor neuron disorders.