Effects of morphine withdrawal on catecholaminergic neurons on heart right ventricle; implication of dopamine receptors

The purpose of our study was to examine the effects of D 1 -and D 2 -dopamine receptors blockade on the changes in the ventricular content of catecholamines in rats withdrawn from morphine. Rats were given morphine by subcutaneous (sc) implantation of morphine pellets for 5 days. On the eighth day,...

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Bibliographic Details
Published in:Canadian journal of physiology and pharmacology 2001-10, Vol.79 (10), p.885-891
Main Authors: Milanés, M V, Marín, M T, Laorden, M L
Format: Article
Language:English
Subjects:
Analgesics, Opioid
Animals
Benzazepines - pharmacology
Biological and medical sciences
Catecholamines - physiology
Dopamine - metabolism
Dopamine Antagonists - pharmacology
Drug addictions
Heart - drug effects
Heart - innervation
Heart Ventricles - drug effects
Heart Ventricles - metabolism
Male
Medical sciences
Morphine
Neurons - physiology
Norepinephrine - metabolism
Rats
Rats, Sprague-Dawley
Receptors, Dopamine - drug effects
Salicylamides - pharmacology
Substance Withdrawal Syndrome - physiopathology
Toxicology
Ventricular Function
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Summary:The purpose of our study was to examine the effects of D 1 -and D 2 -dopamine receptors blockade on the changes in the ventricular content of catecholamines in rats withdrawn from morphine. Rats were given morphine by subcutaneous (sc) implantation of morphine pellets for 5 days. On the eighth day, morphine withdrawal was induced by sc administration of naloxone (1 mg/kg), and rats were killed 30 min later. Pretreatment with SCH 23390 (dopamine D 1 , D 5 receptor antagonist) 15 min prior to naloxone administration suppressed some the behavioural signs of morphine withdrawal, whereas eticlopride (dopamine D 2 , D 3 , D 4 receptor antagonist) did not. In addition, biochemical analysis indicate that SCH 23390 completely abolished the withdrawal-induced increase in noradrenaline and dopamine turnover in the right ventricle. By contrast, eticlopride did not block the hyperactivity of catecholaminergic neurons in the heart during morphine withdrawal. These data suggest that the hyperactivity of catecholaminergic neurons in the heart during morphine withdrawal is dependent upon D 1 dopamine receptor activation. In addition, our results exclude the involvement of D 2 dopamine receptors.Key words: morphine withdrawal, right ventricle, catecholaminergic activity.
ISSN:0008-4212
1205-7541
DOI:10.1139/y01-067