This proposal is the continuation of our efforts to understand the CNS circuitry responsible for coordinating respiratory and vasomotor outflows. The present study focuses on the pathway of the sympathetic reflex triggered by stimulation of carotid chemoreceptors (chemosympathetic reflex). The general goal of the study is to unravel the main CNS relays of this reflex and to characterize some of the transmitters involved. Our main hypothesis is that, under anesthesia, the bulbar pathway of the sympathetic chemoreflex is almost completely separate from that of the baroreflex until the level of the bulbospinal premotor neurons where algebraic summation of the two inputs occurs. Based on preliminary experiments, we also believe that these premotor neurons are located in the rostral ventrolateral medulla and the ponto medullary transitional zone (A5 noradrenergic cells) . We also hypothesize that the sympathetic chemoreflex is mediated via the pre-Botzinger area, a small nucleus of the medulla oblongata responsible for the generation of the respiratory rhythm. This network will be investigated with neurophysiological methods in the anesthetized rat and with a newly introduced neurohistological technique (neuronal expression of the protooncogene product c-fos) which allows the mapping of active CNS networks. These experiments should significantly clarify the central circuitry responsible for the sympathetic chemoreflex, a homeostatic mechanism of fundamental importance in regulating arterial pressure and regional blood flows.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL039841-07
Application #
2219391
Study Section
Respiratory and Applied Physiology Study Section (RAP)
Project Start
1987-09-30
Project End
1997-03-31
Budget Start
1994-04-01
Budget End
1995-03-31
Support Year
7
Fiscal Year
1994
Total Cost
Indirect Cost
Name
University of Virginia
Department
Pharmacology
Type
Schools of Medicine
DUNS #
001910777
City
Charlottesville
State
VA
Country
United States
Zip Code
22904
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Baraban, S C; Stornetta, R L; Guyenet, P G (1995) Effects of morphine and morphine withdrawal on adrenergic neurons of the rat rostral ventrolateral medulla. Brain Res 676:245-57
Baraban, S C; Lothman, E W; Lee, A et al. (1995) Kappa opioid receptor-mediated suppression of voltage-activated potassium current in a catecholaminergic neuronal cell line. J Pharmacol Exp Ther 273:927-33
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Koshiya, N; Huangfu, D; Guyenet, P G (1993) Ventrolateral medulla and sympathetic chemoreflex in the rat. Brain Res 609:174-84
Baraban, S C; Stornetta, R L; Guyenet, P G (1993) Respiratory control of sympathetic nerve activity during naloxone-precipitated morphine withdrawal in rats. J Pharmacol Exp Ther 265:89-95
Huangfu, D; Koshiya, N; Guyenet, P G (1993) Central respiratory modulation of facial motoneurons in rats. Neurosci Lett 151:224-8
Allen, A M; Adams, J M; Guyenet, P G (1993) Role of the spinal cord in generating the 2- to 6-Hz rhythm in rat sympathetic outflow. Am J Physiol 264:R938-45
Huangfu, D; Verberne, A J; Guyenet, P G (1992) Rostral ventrolateral medullary neurons projecting to locus coeruleus have cardiorespiratory inputs. Brain Res 598:67-75
Huangfu, D; Hwang, L J; Riley, T A et al. (1992) Splanchnic nerve response to A5 area stimulation in rats. Am J Physiol 263:R437-46

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