Responses in the white rami communicantes of different segments of the spinal cord to stimulation of the ventral surface of the medulla oblongata

: In anesthetized curarized cats, the responses in T3-4, T10-11 and L2-3 white rami (WR) to stimulation of different zones of the bulbar ventral surface (BVS) were maximal when the region about 4 mm laterally from midline was stimulated. Threshold surface stimulation of all these zones elicited only the long-latency responses in WR. The short-latency responses appeared in WR when supramaximal stimuli were applied to the region up to 6 mm rostrally from the hypoglossal nerve root level (zone S and caudal part of zone M). Descending influences from BVS were conducted by fibers of the spinal dorsolateral funiculus with conduction velocity about 5.6 +/- 0.6 m/sec. These pathways differed from previously studied sympathoexcitatory pathways originating from sympathoexcitatory neurons in caudal medulla. A possible neuronal organization of sympathoexcitatory structures of BVS is suggested.