J Physiol. 1990 September; 428: 371–385.
K Hayes and L C Weaver
In this study, whether RVLM neurons produce differential responses to postganglionic renal, splenic and mesentric nerves were determined. Earlier studies in cats by other suggested that tonic influences from the RVLM to different sympathetic nerves are not uniform in distribution. Glycine was microinjected unilaterally in the RVLM of Urethane anaesthetized male rats. Blockade by glycine produced a greater reductions in the renal than splenic nerve activity with no consistent changes in mesentric nerve activity. Interestingly the preganglionic nerves were not blocked to the same extend as the postganglionic nerves. It is possible that loss of activity in a small number of preganglionic axons could cause a greater loss of activity in the postganglionic neurons since many preganglionic inputs must get together to produce an action potential in the ganglionic cell. The findings from this study suggest that the sympathetic pathways to the kidney are more dependent on the excitatory drive from the RVLM than spleen and intestine. Selective effects of different sympathetic nerves can occur because of topographical organization within the medulla. Questions such as how the brain stem selectively control different sympathetic outflows are yet to be answered.
-Madhan
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