The effect of DOPA and clonidine on reflex pathways from group II muscle afferents to alpha-motoneurones in the cat.

In high spinal cats the transmission in both disynaptic and polysynaptic reflex pathways from group II muscle afferents to motoneurones was effectively depressed by DOPA and clonidine together with an often less pronounced depression of transmission in other FRA reflex pathways. The inhibitory effect of both drugs on the inhibitory group II and FRA pathways was generally less distinct than that on the excitatory ones. The results are in agreement with former observations which suggested that the excitatory and the inhibitory FRA pathways are independently controlled by descending pathways from the brain stem (Holmqvist and Lundberg 1961).