Antihypertensive Effects of Clonidine in Tetraplegic Subjects Devoid of Central Sympathetic Control

1979 ◽  
Vol 57 (s5) ◽  
pp. 425s-428s ◽  
Author(s):  
C. J. Mathias ◽  
J. L. Reid ◽  
L. M. H. Wing ◽  
H. L. Frankel ◽  
N. J. Christensen
Keyword(s):  
Blood Pressure ◽  
Spinal Cord ◽  
Heart Rate ◽  
Cervical Spinal Cord ◽  
Pressor Response ◽  
Plasma Noradrenaline ◽  
Marked Rise ◽  
Indwelling Catheters ◽  
Oral Clonidine ◽  
Noradrenaline And Adrenaline

1. The effects of 300 μg of oral clonidine on blood pressure, heart rate, plasma noradrenaline and adrenaline concentrations were studied in seven tetraplegic subjects with physiologically complete cervical spinal cord transections. 2. Clonidine did not significantly change resting blood pressure during the 8 h of the study. Resting heart rate fell. Resting plasma noradrenaline and adrenaline concentrations, when measured 2 h after clonidine, were not significantly lower. 3. Urinary bladder stimulation resulted in a marked rise in blood pressure accompanied by an elevation in plasma noradrenaline but not adrenaline. The hypertensive response to bladder stimulation was substantially reduced by clonidine, the maximum suppression occurring 2–4 h after administration of the drug. The plasma noradrenaline response to bladder stimulation, when measured 2 h after clonidine, was significantly lower than the response before clonidine. In two tetraplegic subjects with indwelling catheters the rise in intravesical pressure caused by bladder stimulation was unchanged by clonidine. 4. The pressor response to intravenous noradrenaline in two tetraplegic subjects and to intravenous phenylephrine in a further two tetraplegic subjects was unchanged by clonidine. 5. Clonidine may have additional antihypertensive effects which occur independently of actions in the brain. These effects may be exerted by an action either on sympathetic neurones in the spinal cord or on presynaptic α-adrenoreceptors in the periphery.

Differential cardiovascular effects of central clonidine and B-HT 920 in conscious rats

1988 ◽  
Vol 66 (11) ◽  
pp. 1455-1460 ◽  
Author(s):  
Kathryn A. King ◽  
Catherine C. Y. Pang
Keyword(s):  
Heart Rate ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Pressor Response ◽  
Plasma Concentrations ◽  
Cardiovascular Effects ◽  
Plasma Noradrenaline ◽  
Adrenoceptor Agonists ◽  
Noradrenaline And Adrenaline ◽  
Prior Administration

The effect of intracerebroventricular (i.c.v.) injection of the α2-adrenoceptor agonists clonidine and B-HT 920 on mean arterial pressure (MAP), heart rate (HR), and plasma concentrations of noradrenaline and adrenaline was examined in conscious unrestrained rats. The injection of 1.0 μg clonidine significantly decreased MAP and slightly decreased HR. Plasma noradrenaline and adrenaline levels were slightly but not significantly decreased after the injection of 1 μg clonidine. In contrast, the injection of 0.1–10.0 μg B-HT 920 increased MAP and decreased HR. Plasma noradrenaline and adrenaline levels were slightly increased after the injection of the 1- and 10-μg doses. The i.c. v. injection of the α2-antagonist rauwolscine slightly but not significantly increased MAP and plasma noradrenaline and adrenaline levels. The responses to i.c. v. injection of clonidine and B-HT 920 were not changed by prior administration of rauwolscine. Neither the pressor response to B-HT 920 nor the depressor response to clonidine was abolished by rauwolscine, suggesting that neither response was mediated by α2-adrenoceptors.

Plasma Catecholamines do Not Invariably Reflect Sympathetically Induced Changes in Blood Pressure in Man

1983 ◽  
Vol 65 (3) ◽  
pp. 227-235 ◽  
Author(s):  
G. Mancia ◽  
A. Ferrari ◽  
Luisa Gregorini ◽  
G. Leonetti ◽  
G. Parati ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Sympathetic Activity ◽  
Pressor Response ◽  
Plasma Concentrations ◽  
Plasma Catecholamines ◽  
Plasma Noradrenaline ◽  
Carotid Baroreceptor ◽  
Induced Changes ◽  
Neck Chamber ◽  
Noradrenaline And Adrenaline

1. Plasma concentrations of noradrenaline and adrenaline were measured radioenzymatically in nine subjects during 4 min pressor and depressor responses (intra-arterial measurements) induced by increasing and reducing sympathetic vasoconstrictor tone via carotid baroreceptor deactivation and stimulation (neck chamber technique). 2. During the pressor response (15 ± 3 mmHg, mean ± se) plasma noradrenaline and adrenaline showed various changes in the different subjects and on average were not significantly increased above control. During the depressor response (−9 ± 2 mmHg) plasma noradrenaline and adrenaline also showed various changes in the subjects and were on average not significantly reduced below control. 3. In contrast the same subjects all showed an increase in noradrenaline and adrenaline (average 76 and 117%) at the fourth minute of a tilting manoeuvre with- a return to pretilting values no more than 4 min after resumption of the supine position. 4. These results suggest that the moderate and/or restricted alterations in sympathetic tone produced by manipulating a single baroreflex, though capable of affecting blood pressure, are not reflected by alterations in plasma catecholamines. To modify these humoral indices significantly, the more drastic or more diffuse alterations in sympathetic activity that may be produced by manipulating low as well as high pressure reflexogenic areas are needed.

scholarly journals The Effects of Gallamine and a Mixture of Pancuronium and Alcuronium on the Pressor and Plasma Catecholamine Responses to Tracheal Intubation

1984 ◽  
Vol 12 (1) ◽  
pp. 22-26 ◽  
Author(s):  
Mary F. Cummings ◽  
W. J. Russell ◽  
D. B. Frewin ◽  
Wendy A. Miller
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Mean Arterial Pressure ◽  
Tracheal Intubation ◽  
Arterial Pressure ◽  
Plasma Noradrenaline ◽  
Plasma Catecholamine ◽  
Plasma Adrenaline ◽  
Noradrenaline Concentration ◽  
Noradrenaline And Adrenaline

Tracheal intubation can be accompanied by significant increases in arterial pressure, heart rate and the plasma levels of noradrenaline and adrenaline. The drugs used at induction can enhance or attenuate these responses. In nine patients who had received gallamine, intubation was associated with a 45% rise in mean arterial pressure, a twofold rise in plasma adrenaline and a 49% rise in plasma noradrenaline concentration. When a mixture of pancuronium and alcuronium (in a ratio of 4:10 by weight) was used in ten patients, blood pressure fell 24% after induction and rose 49% after intubation. A 24% rise in plasma noradrenaline in response to intubation was also observed. Compared with pancuronium alone, the use of the mixture attentuates the rise in blood pressure and noradrenaline concentration associated with intubation but does not abolish them. In addition, the mixture was associated with a significant fall in blood pressure between induction and intubation, whereas this was not found with gallamine.

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.

Increased Pressor Responsiveness to Enkephalin in Spontaneously Hypertensive Rats: The Role of Vasopressin

1980 ◽  
Vol 59 (s6) ◽  
pp. 235s-237s ◽  
Author(s):  
R. W. Rockhold ◽  
J. T. Crofton ◽  
L. Share
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Pressor Response ◽  
Cardiovascular Effects ◽  
Hypertensive Rats ◽  
Methionine Enkephalin ◽  
Spontaneously Hypertensive ◽  
Wistar Kyoto Rats ◽  
Wistar Kyoto

1. The cardiovascular effects of an enkephalin analogue were examined in spontaneously hypertensive and normotensive Wistar-Kyoto rats. (D-Ala2)-methionine enkephalin caused a biphasic increase in blood pressure and an increase in heart rate after intracerebroventricular injection. 2. The initial pressor response to (D-Ala2)-methionine enkephalin was greater in hypertensive than in normotensive rats. No difference was noted between groups during the secondary pressor response. Heart rate increases paralleled the secondary increase in blood pressure. 3. Naloxone pretreatment abolished the secondary increase in blood pressure and the tachycardia, but did not blunt the initial pressor response in female Wistar-Kyoto rats. 4. Plasma levels of arginine vasopressin were depressed during the plateau phase of the pressor response in hypertensive rats given intracerebroventricular (d-Ala2)-methionine enkephalin. 5. The results suggest that the cardiovascular effects of central enkephalin are not due to vasopressin, but may involve activation of the sympathetic nervous system.

Blood pressure during routine activity, stress, and feeding in black racer snakes (Coluber constrictor)

1993 ◽  
Vol 264 (1) ◽  
pp. R79-R84 ◽  
Author(s):  
J. N. Stinner ◽  
D. L. Ely
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Acute Stress ◽  
Pressor Response ◽  
Routine Activity ◽  
Plasma Norepinephrine ◽  
Arterial Blood ◽  
Coluber Constrictor ◽  
S Peak ◽  
Hematological Changes

The pressor response to normal daily behaviors and acute stress was studied in black racer snakes (Coluber constrictor) at 30 degrees C. In addition, hematological changes during the stress response were assessed. Mean nighttime systemic arterial blood pressure (SABP) in undisturbed snakes was lower than daytime pressure (26 +/- 3 vs. 32 +/- 9 mmHg, P < 0.001). When snakes were fed mice, SABP increased 3.5- to 4-fold and heart rate increased approximately 3-fold above resting values within approximately 30 s (peak SABP, 99 +/- 18 mmHg; peak heart rate, 99 +/- 12 beats/min). Killing and ingesting the mice required 6-15 min, during which time mean SABP and heart rate were 84 +/- 16 mmHg and 92 +/- 12 beats/min. Pulmonary blood pressure also increased but remained 40-50 mmHg lower than SABP. During stress elicited by tapping the snakes for 5-8 min, heart rate was 94 +/- 6 beats/min but SABP averaged only 44 +/- 11 mmHg. Plasma norepinephrine and epinephrine increased 51- and 26-fold. Plasma glucose increased 58%, hematocrit increased 19%, and plasma volume decreased 19%. It is concluded that blood pressure is markedly affected by behavior and that the sympathetic nervous system appears to play a key role.

Effect of Baroreceptor Deafferentation on Central Catecholamines in the Rat

1979 ◽  
Vol 57 (s5) ◽  
pp. 221s-223s ◽  
Author(s):  
Margaret A. Petty ◽  
J. P. Chalmers ◽  
M. Brown ◽  
J. L. Reid
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Tyrosine Hydroxylase ◽  
Brain Stem ◽  
Hydroxylase Activity ◽  
Methyltransferase Activity ◽  
Neurogenic Hypertension ◽  
Noradrenaline Synthesis ◽  
Noradrenaline And Adrenaline ◽  
Sympathetic Efferent Activity

1. Sinoaortic deafferentation in the rat leads to increased blood pressure and heart rate. 2. Early increases in tyrosine hydroxylase activity both in brain stem and hypothalamus suggest that increased noradrenaline synthesis may contribute to the development of neurogenic hypertension. 3. After 4 weeks, phenylethanolamine-N-methyltransferase activity was reduced in the hypothalamus. 4. Noradrenaline- and adrenaline, but not dopamine-containing neurones may participate in regulation of sympathetic efferent activity.

Sign in / Sign up

Export Citation Format

Share Document