Evidence that blood pressure controls heart rate in the chick embryo prior to neural control

Development ◽  
1976 ◽  
Vol 36 (3) ◽  
pp. 685-695
Author(s):  
G. M. Rajala ◽  
J. H. Kalbfleisch ◽  
S. Kaplan

Blood pressure increases will increase heart rate in intact chick embryos, prior to tne development of neural control. Similarly, in surgically isolated hearts, increases in intraventricular fluid pressure will increase the rate of beat. However, fluid pressure applied equally to both interior and exterior surfaces of the isolated heart does not result in increased heart rate. Therefore, we conclude that the increased pressure stretches the heart muscle and that this stretch stimulates the increased heart rate. While heart rate is clearly influenced by blood pressure, the reverse is not true. Propranolol reduces the heart rate to about half normal in intact embryos but does not significantly alter the blood pressure.

1981 ◽  
Vol 51 (4) ◽  
pp. 1023-1026 ◽  
Author(s):  
H. Tazawa

A catheter, consisting of a hypodermic needle and polyethylene tube, was implanted in the allantoic artery and/or vein of chick embryos ranging in incubation ages from 13 to 17 days. The procedure was performed through a small hole opened in the shell (less than 1 cm2). The hole was covered after implantation of the catheter, ensuring the adequate gas exchange by the chorioallantois and physiological values of blood gases. Blood pressure was measured with an electromanometric transducer. The arterial pressure lacked a dicrotic elevation. Both the systolic and diastolic pressures increased markedly with days of incubation, but the heart rate showed no significant change. The venous pressure was pulsatile in some eggs, and the pulsations became prominent after administration of epinephrine.


1981 ◽  
Vol 51 (4) ◽  
pp. 1017-1022 ◽  
Author(s):  
H. Tazawa

Arterial pressure of chick embryos was measured electromanometrically to investigate the effect of altered gaseous environments on blood pressure (BP) and heart rate (HR). The experiments were made in eggs incubated for 14–16 days at 38 degrees C without impeding the diffusive respiratory gas exchange through the shell and chorioallantois. In air, the HR was counted 260–270 beats/min and the BP increased from 14/7 Torr at day 14 to 21/12 Torr at day 16. Both the BP and HR decreased with hypoxia, whereas hyperoxia affected a slight increase in BP and little change in HR. Hypercapnia decreased the HR and tended to enhance a systolic maximum pressure. The effect of hypoxia was augmented markedly in the presence of hypercapnia and vice versa. When N2 was replaced with helium (He), the effect of hypoxia was mitigated significantly. On the contrary, replacement of N2 with sulfur hexafluoride (SF6) augmented the effect of hypoxia. Because the respiratory gas exchange of the egg takes place by diffusion through the shell and chorioallantoic capillaries, the effect of He and SF6 atmospheres on BP and HR is attributed to an altered diffusivity of O2 and CO2 in these inert gases.


Author(s):  
Katarina Targosova ◽  
Matej Kucera ◽  
Zuzana Kilianova ◽  
Lubica Slobodova ◽  
Kristina Szmicsekova ◽  
...  

Nicotinic receptors (NR) play an important role in the cholinergic regulation of heart functions, and converging evidence suggests a diverse repertoire of NR subunits in the heart. A recent hypothesis about the plasticity of β NR subunits suggests that β2 and β4 subunits may substitute for each other. In our study, we assessed the hypothetical β subunit interchangeability in the heart at the level of mRNA. Using two mutant mice strains lacking β2 or β4 NR subunits, we examined the relative expression of NR subunits and other key cholinergic molecules. We investigated the physiology of isolated hearts perfused by Langendorff's method at basal conditions and after cholinergic and/or adrenergic stimulation. Lack of β2 NR subunit was accompanied with decreased relative expression of β4 and α3 subunits. No other cholinergic changes were observed at the level of mRNA, except for increased M3 and decreased M4 muscarinic receptors. Isolated hearts lacking β2 NR subunit showed different dynamics in heart rate response to indirect cholinergic stimulation. In hearts lacking β4 NR subunit, increased levels of β2 subunits were observed together with decreased mRNA for acetylcholine-synthetizing enzyme and M1 and M4 muscarinic receptors. Changes in the expression levels in β4-/- hearts were associated with increased basal heart rate and impaired response to a high dose of acetylcholine upon adrenergic stimulation. In support of the proposed plasticity of cardiac NRs, our results confirmed subunit-dependent compensatory changes to missing cardiac NRs subunits with consequences on isolated heart physiology.


1993 ◽  
Vol 176 (1) ◽  
pp. 223-232
Author(s):  
J. L. Wilkens

Decapod crustacean hearts are suspended by a three-dimensional array of alary ligaments. These ligaments are stretched during systole; diastolic filling via the ostia occurs as the ventricle is stretched by ligamental elastic recoil. There is no direct venous return to the hearts in these animals. In the present study, an isolated heart preparation with intact ligaments, hereafter called in situ, was used to evaluate the effects of artificially induced stretch on heart rate. Strongly beating in situ neurogenic hearts of the crab Carcinus maenas responded to direct perfusion of the ventricle with oxygenated saline and the attendant augmentation of natural stretch with a small increase in heart rate (fh); however, fh was well maintained for up to 15 min after eliminating stretch by cutting the alary ligaments. In contrast to crabs, high rates of artificial perfusion usually depressed fh in crayfish hearts. Crab heart rate falls during hypoxia and this is readily reversed by even low rates of perfusion with oxygenated saline. It is concluded that the gradual decline in fh of totally isolated in vitro hearts arises from the deepening intraventricular hypoxia experienced by the cardiac ganglion.


2007 ◽  
pp. 527-533
Author(s):  
P Skyba ◽  
P Joppa ◽  
M Orolín ◽  
R Tkáčová

Sympathetic activation and parasympathetic withdrawal are commonly observed during acute exacerbations of chronic obstructive pulmonary disease (COPD). We have demonstrated previously that noninvasive positive-pressure ventilation (NPPV) improves parasympathetic neural control of heart rate in patients with obstructive sleep apnea. We hypothesized that NPPV may exert such beneficial effects in COPD as well. Therefore, we assessed the acute effects of NPPV on systemic blood pressure and indexes of heart rate variability (HRV) in 23 patients with acute exacerbations of COPD. The measurements of HRV in the frequency domain were computed by an autoregressive spectral technique. The use of NPPV resulted in significant increases of oxygen saturation (from 89.2+/-1.0 to 92.4+/-0.9 %, p<0.001) in association with reductions in systolic and diastolic blood pressures and heart rate (from 147+/-3 to 138+/-3 mm Hg, from 86+/-2 to 81+/-2 mm Hg, from 85+/-3 to 75+/-2 bpm, p<0.001 for all variables), and increases in ln-transformed high frequency band of HRV (from 6.4+/-0.5 to 7.4+/-0.6 ms(2)/Hz, p<0.01). Reductions in heart rate and increases in ln-transformed HF band persisted after NPPV withdrawal. In conclusion, these findings suggest that NPPV may cause improvements in the neural control of heart rate in patients with acute exacerbations of COPD.


2021 ◽  
Vol 12 ◽  
Author(s):  
Marina Ronzhina ◽  
Tibor Stracina ◽  
Lubica Lacinova ◽  
Katarina Ondacova ◽  
Michaela Pavlovicova ◽  
...  

AimsAlthough voltage-sensitive dye di-4-ANEPPS is a common tool for mapping cardiac electrical activity, reported effects on electrophysiological parameters are rather. The main goals of the study were to reveal effects of the dye on rabbit isolated heart and to verify, whether rabbit isolated heart stained with di-4-ANEPPS is a suitable tool for myocardial ischemia investigation.Methods and ResultsStudy involved experiments on stained (n = 9) and non-stained (n = 11) Langendorff perfused rabbit isolated hearts. Electrophysiological effects of the dye were evaluated by analysis of various electrogram (EG) parameters using common paired and unpaired statistical tests. It was shown that staining the hearts with di-4-ANEPPS leads to only short-term sporadic prolongation of impulse conduction through atria and atrioventricular node. On the other hand, significant irreversible slowing of heart rate and ventricular conduction were found in stained hearts as compared to controls. In patch clamp experiments, significant inhibition of sodium current density was observed in differentiated NG108-15 cells stained by the dye. Although no significant differences in mean number of ventricular premature beats were found between the stained and the non-stained hearts in ischemia as well as in reperfusion, all abovementioned results indicate increased arrhythmogenicity. In isolated hearts during ischemia, prominent ischemic patterns appeared in the stained hearts with 3–4 min delay as compared to the non-stained ones. Moreover, the ischemic changes did not achieve the same magnitude as in controls even after 10 min of ischemia. It resulted in poor performance of ischemia detection by proposed EG parameters, as was quantified by receiver operating characteristics analysis.ConclusionOur results demonstrate significant direct irreversible effect of di-4-ANEPPS on spontaneous heart rate and ventricular impulse conduction in rabbit isolated heart model. Particularly, this should be considered when di-4-ANEPPS is used in ischemia studies in rabbit. Delayed attenuated response of such hearts to ischemia might lead to misinterpretation of obtained results.


1996 ◽  
Vol 85 (5) ◽  
pp. 999-1004 ◽  
Author(s):  
P. Talke ◽  
J. Caldwell ◽  
B. Dodsont ◽  
C. A. Richardson

Background Rapid emergence from anesthesia makes desflurane an attractive choice as an anesthetic for patients having neurosurgery. However, the data on the effect of desflurane on intracranial pressure in humans are still limited and inconclusive. The authors hypothesized that isoflurane and desflurane increase intracranial pressure compared with propofol. Methods Anesthesia was induced with intravenous fentanyl and propofol in 30 patients having transsphenoidal hypophysectomy with no evidence of mass effect, and it was maintained with 70% nitrous oxide in oxygen and a continuous 100 micrograms.kg-2.min-1 infusion of propofol. Patients were assigned to three groups randomized to receive only continued propofol infusion (n = 10), desflurane (n = 10), or isoflurane (n = 10) for 20 min. During the 20-min study period, each patient in the desflurane and isoflurane groups received, in random order, two concentrations (0.5 minimum alveolar concentration [MAC] and 1.0 MAC end-tidal) of desflurane or isoflurane for 10 min each. Lumbar cerebrospinal fluid (CSF) pressure, blood pressure, heart rate, and anesthetic concentrations were monitored continuously. Results Lumbar CSF pressure increased significantly in all patients receiving desflurane or isoflurane. Lumbar CSF pressure increased by 5 +/- 3 mmHg at 1-MAC concentrations of desflurane and by 4 +/- 2 mmHg at 1-MAC concentrations of isoflurane. Cerebral perfusion pressure decreased by 12 +/- 10 mmHg at 1-MAC concentrations of desflurane and by 15 +/- 10 mmHg at 1-MAC concentrations of isoflurane. Heart rate increased by 7 +/- 9 bpm with 0.5 MAC desflurane and by 8 +/- 7 bpm with 1.0 MAC desflurane, and by 5 +/- 11 bpm with 1.0 MAC isoflurane. Systolic blood pressure decreased in all but the patients receiving 1.0 MAC desflurane. To maintain blood pressure within predetermined limits, phenylephrine was administered to six of ten patients in the isoflurane group (range, 25 to 600 micrograms), two of ten patients in the desflurane group (range, 200 to 500 micrograms), and in no patients in the propofol group. Lumbar CSF pressure, heart rate, and systolic blood pressure did not change in the propofol group. Conclusion Desflurane and isoflurane, at 0.5 and 1.0 MAC, increase lumbar CSF pressure.


1998 ◽  
Vol 275 (2) ◽  
pp. H527-H533 ◽  
Author(s):  
Joachim Höchel ◽  
Ryuichi Akiyama ◽  
Takuya Masuko ◽  
James T. Pearson ◽  
Martin Nichelmann ◽  
...  

Heart rate (HR) irregularities in chick embryos were defined as large fluctuations (>10 beats/min) comprising irregular, brief deceleration and/or acceleration of instantaneous HR (IHR). IHR was determined directly from the arterial blood pressure while adequate gas exchange was maintained through an eggshell and chorioallantoic membrane. Five embryos were examined on each day from day 11 to day 19 of incubation. Baseline HR was stable until day 12–13, and on around day 13–14 transient, rapid deceleration of HR (termed V pattern) began to appear, with a subsequent increase in its frequency and magnitude. The acceleration patterns (lambda, avian omega, and periodic patterns) appeared later, and the IHR became increasingly irregular, with additional, spontaneous deceleration and acceleration patterns toward hatching. Additional experiments with intravenous administration of autonomic drugs clearly showed that rapid deceleration of HR was mediated by parasympathetic nervous function but did not always show clear relations of sympathomimetic and sympathetic blocking agents to the acceleration patterns.


1982 ◽  
Vol 60 (2) ◽  
pp. 134-139 ◽  
Author(s):  
G. A. Collins ◽  
B. A. MacLeod ◽  
M. J. A. Walker

The effect of prostacyclin (PGI2) on blood pressure and heart rate (in vivo) and on isolated heart tissue has been investigated in different species. Isolated cardiac tissue had limited resposes to PGI2 tested at 10−13 to 10−5 M. Cultured neonatal rat heart cells did not respond to PGI2, neither did intact rat hearts or rabbit cardiac tissue. Guinea pig and rat atria showed limited dose-dependent responses to PGI2 at concentrations greater than 10−7 M. In rat atria, 10−5 M PGI2 produced a limited elevation of tissue cAMP content. When given by intravenous injection or infusion, PGI2 produced hypotension in anaesthetized primates (three species), rat, rabbit, pig, and dog. As a vasodepressor in all species, PGI2 (on a weight basis) was more active than prostaglandins of the B or E type and, in most species tested, it was approximately five times more active than PGE2. Heart responses in intact animals were often paradoxical in that decreases in heart rate often accompanied blood pressure falls.


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