Differential pattern of spinal sympathetic outflow in response to stimulation of the caudal medullary raphe.
In urethan-anesthetized cats, frequency domain analysis was used to explore the mechanisms of differential responses of inferior cardiac (CN), vertebral (VN), and renal (RN) sympathetic nerves to electrical stimulation of a discrete region of the medullary raphe (0-2 mm caudal to the obex). Raphe stimulation in baroreceptor-denervated cats at frequencies (7-12 Hz) that entrained the 10-Hz rhythm in nerve activity decreased CN and RN activities but increased VN activity. The reductions in CN and RN discharges were associated with decreased low-frequency (</=6 Hz) power and either increased (low stimulus intensity) or decreased (high stimulus intensity) 10-Hz band power. In contrast, VN 10-Hz band power was increased at all stimulus intensities, without changes in low-frequency power. High-frequency (25 Hz) stimulation decreased low-frequency activity of CN and RN discharges in both baroreceptor-denervated and baroreceptor-intact cats, without decreasing VN low-frequency activity. We propose that the differential pattern produced by raphe stimulation involves resonance at the level of the 10-Hz oscillators and differential inhibition of follower circuits that transmit both 10-Hz and low-frequency activity to sympathetic nerves.
Larsen
P D
PD
Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan 48824, USA.
Zhong
S
S
Gebber
G L
GL
Barman
S M
SM
D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D002415:Cats; D004558:Electric Stimulation; D005260:Female; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D010507:Periodicity; D011311:Pressoreceptors / Q000502:physiology; D011903:Raphe Nuclei / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D013116:Spinal Cord / Q000502:physiology*; D013562:Sympathectomy; D013564:Sympathetic Nervous System / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*