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Plasma catecholamine concentrations during morphine withdrawal in conscious guinea-pigs
P J Brent1, P A Johnston, L A Chahl
1Faculty of Medicine, University of Newcastle, New South Wales, Australia.
Clinical and Experimental Pharmacology & Physiology
|August 1, 1987
Summary
Morphine withdrawal in guinea-pigs increases locomotor activity and plasma adrenaline levels, primarily from adrenal medullary release. These changes highlight the interplay between behavior and autonomic responses in opiate dependence.
Area of Science:
- Neuroscience
- Pharmacology
- Autonomic Nervous System
Background:
- Opiate dependence and withdrawal involve complex behavioral and autonomic changes.
- Understanding the neurochemical basis of these responses is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the relationship between plasma catecholamine levels, locomotor activity, and morphine withdrawal in guinea-pigs.
- To differentiate the roles of the adrenal medulla and sympathetic nervous system in morphine withdrawal.
Main Methods:
- Measurements of plasma noradrenaline (NA) and adrenaline (AD) concentrations and locomotor activity in conscious normal and adrenalectomized guinea-pigs.
- Administration of morphine followed by naloxone-precipitated withdrawal.
- Control groups received saline instead of morphine.
Main Results:
- Naloxone injection increased locomotor activity in both intact and adrenalectomized morphine-treated guinea-pigs.
- Plasma AD levels significantly increased during naloxone-precipitated withdrawal in normal guinea-pigs.
- Plasma NA levels were elevated during both morphine treatment and withdrawal.
- Adrenalectomized guinea-pigs showed no detectable plasma AD, confirming adrenal medullary origin of the observed AD increase.
Conclusions:
- Plasma AD concentration and locomotor activity are valuable indicators for studying opiate dependence and withdrawal mechanisms.
- Morphine and its withdrawal differentially affect the autonomic nervous system in guinea-pigs, with adrenal medullary release of AD being a key component of withdrawal.