AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 3 752-R758, Copyright © 1995 by American Physiological Society
Cuneiform nucleus stimulation produces activation of medullary sympathoexcitatory neurons in rats
A. J. Verberne
University of Melbourne, Clinical Pharmacology and Therapeutics Unit, Austin Hospital, Heidelberg, Victoria, Australia.
Activation of the cuneiform nucleus (CNF) of the midbrain produces
elevation of arterial blood pressure. This study examined the influence of
the CNF on arterial blood pressure, sympathetic vasomotor outflow, and the
discharges of barosensitive sympathoexcitatory neurons of the rostral
ventrolateral medulla (RVLM) in halothane-anesthetized, paralyzed rats.
Electrical stimulation (50 Hz, 25-75 microA, 10 s) of the CNF elicited
intensity-dependent elevations in arterial blood pressure associated with
excitation of the sympathetic vasomotor discharge (elevated discharge of
the lumbar sympathetic nerve). Intermittent paired-pulse electrical
stimulation of the CNF elicited an excitatory response in the discharge of
the lumbar sympathetic outflow that consisted of an early peak (onset
latency 84 +/- 4 ms) and a smaller late peak (onset latency 217 +/- 6 ms).
Seventeen of 22 RVLM sympathoexcitatory neurons tested were excited by
stimulation of the CNF. Twelve of 14 units tested projected to the thoracic
spinal cord, and of these, 10 units were excited by CNF stimulation with an
onset latency of 16 +/- 1 ms. These findings support the hypothesis that
the sympathoexcitatory and pressor responses elicited by activation of the
CNF are mediated by RVLM sympathoexcitatory neurons.
