ROLE OF THE BRAIN-STEM IN GENERATING THE 2-HZ TO 6-HZ OSCILLATION IN SYMPATHETIC-NERVE DISCHARGE

We tested the hypothesis that brain stem circuits normally generate a 2- to 6-Hz oscillation in sympathetic nerve discharge (SND). Experimen ts were performed on baroreceptor-denervated decerebrate cats and uret han-anesthetized rats in which renal or splanchnic SND was recorded al ong with field potentials (population activity) from sites in the rost ral ventrolateral medulla, medullary raphe, or medullary lateral tegme ntal field. Our major findings were as follows. 1) Population activity recorded from the three medullary regions contained a 2- to 6-Hz osci llation. 2) The 2- to 6-Hz oscillation in population activity recorded from some medullary sites was correlated to that in SND. Peak coheren ce in the 2- to 6-Hz band approached a value of 1 in some cases. 3) Wh ereas cervical spinal cord transection abolished or markedly reduced S ND, the 2- to 6-Hz oscillation in medullary activity was essentially u nchanged. These results support the view that the 2- to 6-Hz oscillati on in SND can be generated in the brain stem of cats and rats.