Connections of Barrington's nucleus to the sympathetic nervous system in rats

Barrington's nucleus (BN) has been considered a pontine center related excl usively to the control of pelvic parasympathetic activity. The present stud y demonstrates an anatomical linkage between BN and autonomic outflow to vi sceral targets innervated exclusively by the sympathetic division of the au tonomic nervous system. Temporal analysis of infection after injection of p seudorabies virus (PRV), a retrograde transynaptic tracer, into two sympath etically innervated organs, the spleen and the kidney, revealed the presenc e of infected neurons in BN at early post-inoculation survival intervals. I mmunohistochemical localization of PRV after spleen injections showed that a small subpopulation of BN neurons became labeled in a time frame coincide nt with the appearance of infected neurons in other brain regions known to project to sympathetic preganglionic neurons (SPNs) in the thoracic spinal cord; a larger number of infected neurons appeared in BN at intermediate in tervals after PRV injections into the spleen or kidney. Coinjection of the retrograde tracer Fluoro-Gold i.p. and PRV into the spleen demonstrated tha t parasympathetic preganglionic neurons in the caudal medulla or lumbo-sacr al spinal cord were not infected, indicating that infected BN neurons were not infected via a parasympathetic route. Thus, BN neurons become infected after PRV injections into the spleen or kidney either directly through BN p rojections to SPNs, or secondarily via BN projections to infected pre-prega nglionic neurons. These results demonstrate an anatomical linkage, either d irect or indirect, between BN and sympathetic activity. Because BN receives numerous inputs from diverse brain regions, the relation of BN with both b ranches of the autonomic nervous system suggests that this nucleus might pl ay a role in the integration of supraspinal inputs relevant to the central coordination of sympathetic and parasympathetic activity. (C) 2000 Publishe d by Elsevier Science B.V. All rights reserved.