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Central haemodynamics during morphine abstinence in anaesthetized rats
M Delle1, P Thorén, S E Ricksten
1Department of Physiology, University of Göteborg, Sweden.
Acta Physiologica Scandinavica
|December 1, 1988
Summary
Naloxone administration in morphine-dependent rats significantly increased mean arterial pressure (MAP) by raising total peripheral resistance (TPR). This suggests withdrawal hypertension is primarily due to increased resistance vessel tone, not central blood volume changes.
Area of Science:
- Pharmacology
- Cardiovascular Physiology
- Neuroscience
Background:
- Morphine dependence affects central hemodynamics.
- Naloxone is an opioid antagonist used to reverse opioid effects.
Purpose of the Study:
- To investigate the hemodynamic effects of naloxone in morphine-dependent rats.
- To elucidate the mechanisms underlying naloxone-induced changes in blood pressure and related cardiovascular parameters.
Main Methods:
- Central hemodynamic variables (MAP, HR, CO, MTT) were measured in conscious and anesthetized morphine-dependent and control rats.
- Naloxone was administered intravenously at escalating doses.
- Calculations included TPR, SV, and CBV.
Main Results:
- Morphine-dependent rats showed a greater drop in MAP upon anesthesia, linked to decreased TPR.
- Naloxone administration markedly increased MAP in dependent rats, primarily via TPR elevation.
- Naloxone did not significantly alter CO or CBV but increased SV and decreased HR in dependent rats.
Conclusions:
- Morphine withdrawal hypertension is mainly driven by increased total peripheral resistance, indicating augmented resistance vessel tone.
- Naloxone-induced abstinence minimally affects central blood volume, suggesting venous capacitance vessels are largely unaffected.