Site of central chemosensitivity in fetal sheep

1975 ◽  
Vol 39 (1) ◽  
pp. 1-6 ◽  
Author(s):  
A. H. Jansen ◽  
V. Chernick
Keyword(s):  
Blood Pressure ◽  
Spinal Cord ◽  
Heart Rate ◽  
Respiratory Response ◽  
Fetal Sheep ◽  
Central Chemosensitivity ◽  
Cord Clamping ◽  
Chemosensitive Areas ◽  
Ventral Medullary Surface ◽  
Histotoxic Hypoxia

The heart rate, blood pressure, and respiratory response to topically applied cyanide on the ventrolateral medullary surface and upper spinal cord was studied on exteriorized sinaortic-denervated fetal lambs under pentobarbital anesthesia. On all sites tested cyanide produced a rapid increase in heart rate and blood pressure (P smaller than 0.05) which was most pronounced from the area adjacent to the nerve roots IX to XI (mean 32%). Respiratory efforts consisting of 1–8 gasps were induced in half the applications to the medulla but never when the pledgets were applied to the spinal cord. The mean delay to response was 43 s (range 13–102 s). After cautery of the chemosensitive areas, topical application of cyanide failed to stimulate gasping, whereas intravenous cyanide or cord clamping still produced a vigorous respiratory response. It is concluded that sympathetic stimulation of the heart and blood vessels can originate centrally in response to local histotoxic hypoxia of the ventral medulla and upper spinal cord. Furthermore, it is proposed that in the apneic fetus histotoxic hypoxia of the medulla initiates respiration possibly by stimulating a special gasping mechanism which is separate from the respiratory center responsible for rhythmic breathing after birth. The responsible neurons must be located at least 2 mm beneath the ventral medullary surface.

Diurnal Blood Pressure Variation in Quadriplegic Chronic Spinal Cord Injury Patients

1991 ◽  
Vol 80 (3) ◽  
pp. 271-276 ◽  
Author(s):  
Henry Krum ◽  
William J. Louis ◽  
Douglas J. Brown ◽  
Graham P. Jackman ◽  
Laurence G. Howes
Keyword(s):  
Blood Pressure ◽  
Spinal Cord ◽  
Heart Rate ◽  
Spinal Cord Injury ◽  
Ambulatory Monitoring ◽  
Pressure Variation ◽  
Night Time ◽  
Cord Injury ◽  
Blood Pressure Variation ◽  
Neurologically Intact

1. Measurement of blood pressure and heart rate over a 24 h period was peformed in 10 quadriplegic spinal cord injury patients and 10 immobilized, neurologically intact orthopaedic subjects by using the Spacelabs 90207 automated ambulatory monitoring system. 2. Systolic and diastolic blood pressure fell significantly at night in orthopaedic subjects but not in quadriplegic patients, and night-time blood pressures were similar in both groups. 3. Cumulative summation of differences from a reference value (cusum analysis) confirmed a markedly diminished diurnal blood pressure variation in the quadriplegic patients. 4. These findings could not be accounted for on the basis of blood pressure variations during chronic postural change. 5. Heart rate fell significantly at night in both groups. 6. The findings suggest that the increase in blood pressure during waking hours in neurologically intact subjects is a consequence of a diurnal variation in sympathetic activity (absent in quadriplegic patients with sympathetic decentralization) which is independent of changes in physical activity.

Effects of spinal cord transection on sympathetic discharge in decerebrate-unanesthetized cats

1989 ◽  
Vol 257 (6) ◽  
pp. R1506-R1511 ◽  
Author(s):  
L. C. Weaver ◽  
R. D. Stein
Keyword(s):  
Blood Pressure ◽  
Spinal Cord ◽  
Heart Rate ◽  
Spectral Analysis ◽  
Spinal Cord Transection ◽  
Renal Nerves ◽  
Frequency Range ◽  
Renal Nerve ◽  
Sympathetic Discharge ◽  
Nerve Discharge

Previous experiments in our laboratory have shown that discharge of splenic, mesenteric, and splanchnic nerves is well maintained after spinal cord transection in chloralose-anesthetized cats (8, 9, 11). The primary purpose of this investigation was to determine if maintained sympathetic discharge could be observed after spinal transection in the absence of chloralose anesthesia. In cats anesthetized with alphaxalone-alphadolone, changes in splanchnic discharge, blood pressure, and heart rate caused by decerebration and removal of the forebrain were observed. This procedure decreased blood pressure, increased heart rate, and had no immediate effect on sympathetic discharge or its rhythm (assessed by power density spectral analysis). One hour after decerebration and termination of anesthesia, splanchnic discharge had increased by approximately 36%. Next, effects of spinal cord transection on discharge of splanchnic, mesenteric, and renal nerves were observed in the decerebrate-unanesthetized cats. Splanchnic discharge decreased by 50%, mesenteric nerve discharge was unchanged, and renal nerve discharge decreased by 97%. Therefore, splanchnic nerve discharge was not as well maintained in decerebrate-unanesthetized cats as it had been in chloralose-anesthetized animals, and the remaining splanchnic discharge appeared to affect mesenteric nerves preferentially. Finally, spectral analysis of the splanchnic discharge demonstrated that before cord transection, most of the signal was in the 0- to 6-Hz frequency range, whereas after transection the proportion of signal in this frequency range was significantly reduced and the proportion in higher frequencies (7-25 Hz) was significantly increased. This loss of low-frequency rhythmicity is consistent with findings in our previous studies in chloralose-anesthetized cats.

scholarly journals Role of respiration in the cardiovascular response to orthostatic and mental stress

2018 ◽  
Vol 314 (6) ◽  
pp. R761-R769 ◽  
Author(s):  
Michal Javorka ◽  
Fatima El-Hamad ◽  
Barbora Czippelova ◽  
Zuzana Turianikova ◽  
Jana Krohova ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Respiratory Sinus Arrhythmia ◽  
Mental Stress ◽  
Blood Pressure Variability ◽  
Mental Arithmetic ◽  
Cardiovascular Response ◽  
Respiratory Response ◽  
Sinus Arrhythmia ◽  
Head Up Tilt

The objective of this study was to determine the response of heart rate and blood pressure variability (respiratory sinus arrhythmia, baroreflex sensitivity) to orthostatic and mental stress, focusing on causality and the mediating effect of respiration. Seventy-seven healthy young volunteers (46 women, 31 men) aged 18.4 ± 2.7 yr underwent an experimental protocol comprising supine rest, 45° head-up tilt, recovery, and a mental arithmetic task. Heart rate variability and blood pressure variability were analyzed in the time and frequency domain and modeled as a multivariate autoregressive process where the respiratory volume signal acted as an external driver. During head-up tilt, tidal volume increased while respiratory rate decreased. During mental stress, breathing rate increased and tidal volume was elevated slightly. Respiratory sinus arrhythmia decreased during both interventions. Baroreflex function was preserved during orthostasis but was decreased during mental stress. While sex differences were not observed during baseline conditions, cardiovascular response to orthostatic stress and respiratory response to mental stress was more prominent in men compared with women. The respiratory response to the mental arithmetic tasks was more prominent in men despite a significantly higher subjectively perceived stress level in women. In conclusion, respiration shows a distinct response to orthostatic versus mental stress, mediating cardiovascular variability; it needs to be considered for correct interpretation of heart rate and blood pressure phenomena.

scholarly journals Reno-Renal and Reno-Adrenal Reflexes in the Rat

1980 ◽  
Vol 59 (s6) ◽  
pp. 323s-325s ◽  
Author(s):  
G. Recordati ◽  
S. Genovesi ◽  
D. Cerati ◽  
R. Di Cintio
Keyword(s):  
Blood Pressure ◽  
Spinal Cord ◽  
Heart Rate ◽  
Nervous System ◽  
Renal Artery ◽  
Sympathetic Activity ◽  
Nerve Activity ◽  
Natural Stimuli ◽  
Anaesthetized Rats ◽  
Excitatory Responses

1. Experiments were carried out to investigate whether the activation of renal chemoceptive receptors by natural stimuli might induce reflex alterations of efferent postganglionic activity to the ipsilateral kidney and preganglionic activity to the ipsilateral adrenal. 2. In anaesthetized rats with intact nervous system back-flow of urine and occlusion of the renal artery were accompanied by increments in efferent sympathetic activity both to the kidney and adrenal without concomitant changes in heart rate and blood pressure. 3. Greater excitatory responses in nerve activity to the same test stimuli were observed in rats with the spinal cord cut at C1. 4. These results indicate that the natural activation of renal chemoceptive receptors might induce reno-renal and reno-adrenal excitatory reflexes which are likely to be integrated at spinal and supraspinal levels.

Effects of lidocaine on heart rate, blood pressure, and electrocorticogram in fetal sheep

1974 ◽  
Vol 118 (7) ◽  
pp. 935-949 ◽  
Author(s):  
K. Teramo ◽  
N. Benowitz ◽  
M.A. Heymann ◽  
K. Kahanpää ◽  
A. Siimes ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Fetal Sheep
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