Related Experiment Videos
Dual action of morphine on fetal breathing movements
Abstract:
Morphine has been reported to both stimulate and suppress fetal breathing movements (FBM). In light of these conflicting reports, we have conducted a systematic dose-response analysis of the effects of morphine on FBM in 27 fetal lambs. Morphine was infused directly to the fetus in doses ranging from 0.075 to 80 mg/hr. Low doses (0.075-2.5 mg/hr) resulted in a progressive increase in the relative incidence of FBM, whereas higher doses (greater than 2.5 mg/hr) decreased FBM with total apnea observed at 80 mg/hr. This biphasic response can be fitted as the sum of two sigmoidal log dose-response curves. Both stimulation and suppression of FBM by morphine were abolished by naloxone pretreatment, indicating that both responses are mediated by activation of opioid receptors. The dual action of morphine on FBM may be due to different opioid receptor subtypes or different sites of action.
Insights
Morphine has a dual effect on fetal breathing movements (FBM). Low doses stimulate FBM, while high doses suppress them, indicating complex opioid receptor interactions.
Area of Science:
- Pharmacology
- Neuroscience
- Developmental Biology
Background:
- Conflicting reports exist regarding morphine's impact on fetal breathing movements (FBM).
- Understanding these effects is crucial for perinatal care and fetal development research.
Purpose of the Study:
- To systematically investigate the dose-response relationship of morphine on FBM in fetal lambs.
- To elucidate the mechanisms underlying morphine's dual action on FBM.
Main Methods:
- A systematic dose-response analysis was performed on 27 fetal lambs.
- Morphine was administered via direct fetal infusion across a range of doses (0.075–80 mg/hr).
- Naloxone pretreatment was used to assess opioid receptor involvement.
Main Results:
- Low-dose morphine (0.075–2.5 mg/hr) progressively increased FBM incidence.
- High-dose morphine (>2.5 mg/hr) decreased FBM, leading to apnea at 80 mg/hr.
- Both stimulation and suppression of FBM by morphine were blocked by naloxone.
Conclusions:
- Morphine exhibits a biphasic effect on fetal breathing movements, stimulating at low doses and suppressing at high doses.
- These dose-dependent effects are mediated by opioid receptors.
- The dual action may involve different opioid receptor subtypes or distinct sites of action.