ABSTRACT
OBJECTIVE: To examine the impact of age on the effects of desipramine (DMI) on autonomic input to the heart. METHOD: Twenty-four-hour electrocardiograms were obtained from 42 subjects, aged 7 to 66 years, while off and on DMI. To obtain measures of autonomic input to the heart, heart rate variability was assessed via spectral analysis of RR interval variability. RESULTS: DMI treatment was associated with a significant increase in 24-hour mean heart rate and significant decreases in RR interval variability in all spectral bands, including in the high-frequency band, which provides a measure of parasympathetic input to the heart. RR interval variability was greater in younger individuals both off and on DMI. CONCLUSIONS: DMI treatment was associated with a marked decline in RR interval variability, indicating that DMI affects autonomic input to the heart. Specifically, DMI reduced parasympathetic input, which, in theory, may increase vulnerability to arrhythmias. However, the magnitude of DMI's impact on RR interval variability did not vary with age.
Subject(s)
Antidepressive Agents, Tricyclic/pharmacology , Desipramine/pharmacology , Heart Rate/drug effects , Adolescent , Adult , Age Factors , Aged , Arrhythmias, Cardiac/chemically induced , Arrhythmias, Cardiac/physiopathology , Child , Female , Heart/innervation , Humans , Male , Middle Aged , Parasympathetic Nervous System/drug effects , Parasympathetic Nervous System/physiologyABSTRACT
OBJECTIVE: In light of recent reports of sudden death in children being treated with desipramine (DMI), 3 of which were associated with physical exercise, the authors examined the effects of DMI on exercise in children and adults before and during DMI treatment. METHOD: Before treatment, 22 subjects (9 children, 13 adults) participated in a graded treadmill exercise test. Outcome measures included exercise tolerance, cardiovascular, and electrocardiographic parameters at progressive intensity levels and serum norepinephrine (NE) levels before and after exercise testing. Subjects were then treated with DMI, titrated to an average DMI dosage of 3 mg/kg, and underwent repeated exercise testing. RESULTS: DMI treatment was associated with a significant elevation of circulating NE levels in the pre-exercise assessment. Exercise tolerance was not affected by DMI, and blood pressure and heart rate effects were modest. The cardiovascular impact of DMI treatment was similar in children and adults. One 31-year-old subject exhibited a brief episode of ventricular tachycardia associated with exercise during DMI treatment. CONCLUSIONS: DMI has only minor effects on the cardiovascular response to exercise, and these effects do not appear age-related. However, DMI may increase the risk of exercise-associated arrhythmias in rare individuals.
Subject(s)
Antidepressive Agents, Tricyclic/pharmacology , Cardiovascular System/drug effects , Depression/prevention & control , Desipramine/pharmacology , Exercise Test/drug effects , Adolescent , Adult , Age Factors , Antidepressive Agents, Tricyclic/adverse effects , Arrhythmias, Cardiac/etiology , Blood Pressure/drug effects , Child , Desipramine/adverse effects , Exercise , Exercise Tolerance/drug effects , Female , Heart Rate/drug effects , Humans , Male , Norepinephrine/bloodABSTRACT
Two periods in the activity of cell are distinguished during the first three hours after partial hepatectomy. The first period (about 0.5 h) is characterized by the activation of RNA synthesis in all the compartments of the cell, including mitochondria, and by approach of the latter to the nucleus, which is probably induced by the demand of a great quantity of energy for both the present and subsequent intranuclear synthesis. These data have permitted referring the response of hepatocytes in the first period to nonspecific ones. The second period (0.5-3 h) is distinguished by the differentiated response of hepatocytes to the proliferative stimulus.
