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Effects of morphine on isolated right atria of the rat
M Romero1, M L Laorden, J Hernández
1Department of Pharmacology, Medical School of Sevilla, Spain.
Abstract:
1. The present study describes the effects of morphine in the absence or presence of naloxone or atropine in the isolated right atria of the rat. 2. Morphine significantly decreased the auricular chronotropism. 3. The maximal effect was 10 +/- 1.0%. 4. Similar results were obtained in reserpinized animals (13 +/- 0.2% maximum). 5. Naloxone (5 x 10(-7) or 5 x 10(-6) M) did not change the inhibitory effects induced by morphine. 6. The maximal effect obtained with morphine in the presence of atropine (5 x 10(-7) M) was 9 +/- 0.1% similar to that obtained with morphine alone. 7. These results suggest that opioid or vagal mechanisms may not be involved in the cardiac inhibitory effects induced by morphine.
Insights
Morphine reduced heart rate in isolated rat atria. This effect was not altered by naloxone or atropine, suggesting opioid or vagal pathways are not involved in morphine
Area of Science:
- Pharmacology
- Cardiovascular Physiology
- Neuroscience
Background:
- Morphine is a potent opioid analgesic.
- Its effects on cardiac function are not fully elucidated.
- Understanding morphine's cardiac impact is crucial for clinical use.
Purpose of the Study:
- To investigate the effects of morphine on isolated rat right atria.
- To determine the involvement of opioid and vagal mechanisms in morphine-induced cardiac changes.
Main Methods:
- Isolated right atria from rats were used.
- Experiments were conducted with and without naloxone or atropine.
- Auricular chronotropism was measured to assess cardiac function.
Main Results:
- Morphine significantly decreased auricular chronotropism by a maximum of 10%.
- This effect persisted in reserpinized animals.
- Naloxone and atropine did not modify morphine's inhibitory cardiac effects.
Conclusions:
- Opioid receptors do not appear to mediate morphine's negative chronotropic effect.
- Vagal mechanisms are unlikely to be involved in morphine's cardiac inhibition.
- Morphine exerts a direct inhibitory effect on atrial chronotropism.