Role of the spinal cord in generating the 2- to ~-HZ rhythm in rat sympathetic outflow

Guyenet. Role of the spinal cord in generating the 2- to ~-HZ rhythm in rat sympathetic outflow. Am. J. Physiol. 264 (Regu-latory Integrative Comp. Physiol. 33): R938-R945, 1993.-In baroreceptor-denervated animals, sympathetic nerve discharge (SND) displays a 2- to ~-HZ rhythm. Current theories suggest that this rhythm is generated by a neural oscillator in the me-dulla. In urethan-anesthetized rats, we have examined the effect on the 2- to ~-HZ rhythm of lumbar SND produced by 1) alter-ing the firing pattern of a major output of this medullary net-work [the rostra1 ventrolateral medulla (RVLM)] and 2) dis-rupting the interactions between medulla and spinal cord (SC). Microinjection of muscimol [ y-aminobutyric acid (GABA) ag-onist] unilaterally or a mixture of kynurenic acid (KYN; broad spectrum, excitatory amino acid antagonist) and bicuculline (GABA * antagonist) bilaterally into RVLM produced little ef