Abstract
Study objective - The aim of the study was to evaluate the effect of chronic digoxin therapy on cardiac sensitivity to isoprenaline.Design - Responses to isoprenaline were examined in both conscious and anaesthetised dogs pretreated with digoxin, and compared with conscious or anaesthetised controls with no digoxin pretreatment. Isoprenaline infusion (0.001-0.1 μg·kg-1·min-1) in pretreated groups was performed 7 d after digoxin dosing was stopped, when plasma digoxin concentrations were zero.Subjects - Mongrel dogs of either sex (15-25 kg) were used in the experiments, done under anaesthetic. They were divided into three groups (n=6 per group): group A were controls; groups B and C were pretreated with digoxin 500-750 μg.d-1, for 14 d (B) and 7 d (C). For the experiments in conscious animals, six mongrel dogs (25-30 kg) and two greyhounds (25-30 kg) were used; group D (n=6) were treated with digoxin for 20-40 d; group E (n=2) were treated for 7 d.Measurements and results - Heart rate, blood pressure and myocardial contractility (dP/dt: integrated isometric tension) were measured during isoprenaline infusion. Digoxin pretreatment for 14 d did not significantly change the chronotropic or depressor responses to isoprenaline in anaesthetised dogs but there was a 10-fold increase in inotropic sensitivity to isoprenaline following withdrawal. When the pretreatment period was reduced to 7 d there was no change in any of the responses to isoprenaline. In conscious dogs there was also a significant increase in inotropic sensitivity to isoprenaline after digoxin withdrawal, but this was not so marked as in anaesthetised dogs. In conscious dogs chronotropic sensitivity to isoprenaline was also increased.Conclusions - It is possible that the inotropic effect maintained during the 2 weeks of digoxin treatment may cause substantial withdrawal of sympathetic tone to the heart, with a consequent increase in β adrenoceptor number or sensitivity, which could be detected a week after digoxin withdrawal.
| Language | English |
|---|---|
| Pages | 222-226 |
| Number of pages | 5 |
| Journal | Cardiovascular Research |
| Volume | 24 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - Mar 1990 |
| Externally published | Yes |
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Keywords
- β adrenoceptor
- Anaesthetised
- Chronotropic
- Conscious
- Digoxin
- Dog
- Inotropic
- Isoprenaline
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Increased sensitivity to isoprenaline following digoxin pretreatment in anaesthetised and conscious dogs. / Mihailidou, Anastasia S.; Einstein, Rosemarie; Richardson, Desmond P.; Gray, Peter; Jones, Michael P.; Hunyor, Stephen N.
In: Cardiovascular Research, Vol. 24, No. 3, 03.1990, p. 222-226.Research output: Contribution to journal › Review article › Research › peer-review
TY - JOUR
T1 - Increased sensitivity to isoprenaline following digoxin pretreatment in anaesthetised and conscious dogs
AU - Mihailidou, Anastasia S.
AU - Einstein, Rosemarie
AU - Richardson, Desmond P.
AU - Gray, Peter
AU - Jones, Michael P.
AU - Hunyor, Stephen N.
PY - 1990/3
Y1 - 1990/3
N2 - Study objective - The aim of the study was to evaluate the effect of chronic digoxin therapy on cardiac sensitivity to isoprenaline.Design - Responses to isoprenaline were examined in both conscious and anaesthetised dogs pretreated with digoxin, and compared with conscious or anaesthetised controls with no digoxin pretreatment. Isoprenaline infusion (0.001-0.1 μg·kg-1·min-1) in pretreated groups was performed 7 d after digoxin dosing was stopped, when plasma digoxin concentrations were zero.Subjects - Mongrel dogs of either sex (15-25 kg) were used in the experiments, done under anaesthetic. They were divided into three groups (n=6 per group): group A were controls; groups B and C were pretreated with digoxin 500-750 μg.d-1, for 14 d (B) and 7 d (C). For the experiments in conscious animals, six mongrel dogs (25-30 kg) and two greyhounds (25-30 kg) were used; group D (n=6) were treated with digoxin for 20-40 d; group E (n=2) were treated for 7 d.Measurements and results - Heart rate, blood pressure and myocardial contractility (dP/dt: integrated isometric tension) were measured during isoprenaline infusion. Digoxin pretreatment for 14 d did not significantly change the chronotropic or depressor responses to isoprenaline in anaesthetised dogs but there was a 10-fold increase in inotropic sensitivity to isoprenaline following withdrawal. When the pretreatment period was reduced to 7 d there was no change in any of the responses to isoprenaline. In conscious dogs there was also a significant increase in inotropic sensitivity to isoprenaline after digoxin withdrawal, but this was not so marked as in anaesthetised dogs. In conscious dogs chronotropic sensitivity to isoprenaline was also increased.Conclusions - It is possible that the inotropic effect maintained during the 2 weeks of digoxin treatment may cause substantial withdrawal of sympathetic tone to the heart, with a consequent increase in β adrenoceptor number or sensitivity, which could be detected a week after digoxin withdrawal.
AB - Study objective - The aim of the study was to evaluate the effect of chronic digoxin therapy on cardiac sensitivity to isoprenaline.Design - Responses to isoprenaline were examined in both conscious and anaesthetised dogs pretreated with digoxin, and compared with conscious or anaesthetised controls with no digoxin pretreatment. Isoprenaline infusion (0.001-0.1 μg·kg-1·min-1) in pretreated groups was performed 7 d after digoxin dosing was stopped, when plasma digoxin concentrations were zero.Subjects - Mongrel dogs of either sex (15-25 kg) were used in the experiments, done under anaesthetic. They were divided into three groups (n=6 per group): group A were controls; groups B and C were pretreated with digoxin 500-750 μg.d-1, for 14 d (B) and 7 d (C). For the experiments in conscious animals, six mongrel dogs (25-30 kg) and two greyhounds (25-30 kg) were used; group D (n=6) were treated with digoxin for 20-40 d; group E (n=2) were treated for 7 d.Measurements and results - Heart rate, blood pressure and myocardial contractility (dP/dt: integrated isometric tension) were measured during isoprenaline infusion. Digoxin pretreatment for 14 d did not significantly change the chronotropic or depressor responses to isoprenaline in anaesthetised dogs but there was a 10-fold increase in inotropic sensitivity to isoprenaline following withdrawal. When the pretreatment period was reduced to 7 d there was no change in any of the responses to isoprenaline. In conscious dogs there was also a significant increase in inotropic sensitivity to isoprenaline after digoxin withdrawal, but this was not so marked as in anaesthetised dogs. In conscious dogs chronotropic sensitivity to isoprenaline was also increased.Conclusions - It is possible that the inotropic effect maintained during the 2 weeks of digoxin treatment may cause substantial withdrawal of sympathetic tone to the heart, with a consequent increase in β adrenoceptor number or sensitivity, which could be detected a week after digoxin withdrawal.
KW - β adrenoceptor
KW - Anaesthetised
KW - Chronotropic
KW - Conscious
KW - Digoxin
KW - Dog
KW - Inotropic
KW - Isoprenaline
UR - http://www.scopus.com/inward/record.url?scp=0025056943&partnerID=8YFLogxK
U2 - 10.1093/cvrese/24.3.222
DO - 10.1093/cvrese/24.3.222
M3 - Review article
VL - 24
SP - 222
EP - 226
JO - Cardiovascular Research
T2 - Cardiovascular Research
JF - Cardiovascular Research
SN - 0008-6363
IS - 3
ER -