Synaptic responses of reticulospinal neurons in the cat: spinal cord dorsal funiculi are an effective source

Stimulation of spinal cord dorsal funiculi (DF), as compared with stimulation of ventrolateral fascicle (VLF) in which the spinoreticular pathways are located, activated a higher percentage of reticulospinal (RS) neurons (95% vs. 75%). Polysynaptic EPSPs evoked from DF at C2 segment had shorter latency (10.1 msec +/- vs. VLF C2-13.2 msec +/- 0.9-mean +/- S.E.M.). When the intensity of stimulation was close to threshold (1.5 T), EPSPs from DF had steeper slopes on the increasing phase and were of longer duration. Threshold for setting up of synaptic activity from DF at the majority of observed RS neurons was low; recording of antidromic responses in hindlimb nerves showed that fast-conducting myelinized afferents were activated. The functional connection between DF and RS systems may participate in prompt and generalized reflex reactions.