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Updated: Jul 9, 2025
Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
Published on: July 29, 2014
Morphine aggravates inflammatory, behavioral, and hippocampal structural deficits in septic rats
Evans O Ayieng'a1, Elham A Afify2, Salwa A Abuiessa1
1Department of Pharmacology and Toxicology, Faculty of Pharmacy, Alexandria University, 1-El-Khartoum Square-Azarita, Alexandria, 21521, Egypt.
Abstract:
Although pain and sepsis are comorbidities of intensive care units, reported data on whether pain control by opioid analgesics could alter inflammatory and end-organ damage caused by sepsis remain inconclusive. Here, we tested the hypothesis that morphine, the gold standard narcotic analgesic, modifies behavioral and hippocampal structural defects induced by sepsis in male rats. Sepsis was induced with cecal ligation and puncture (CLP) and behavioral studies were undertaken 24 h later in septic and/or morphine-treated animals. The induction of sepsis or exposure to morphine (7 mg/kg) elicited similar: (i) falls in systolic blood pressure, (ii) alterations in spatial memory and learning tested by the Morris water maze, and (iii) depression of exploratory behavior measured by the new object recognition test. These hemodynamic and cognitive defects were significantly exaggerated in septic rats treated with morphine compared with individual interventions. Similar patterns of amplified inflammatory (IL-1β) and histopathological signs of hippocampal damage were noted in morphine-treated septic rats. Additionally, the presence of intact opioid receptors is mandatory for the induction of behavioral and hemodynamic effects of morphine because no such effects were observed when the receptors were blocked by naloxone. That said, our findings suggest that morphine provokes sepsis manifestations of inflammation and interrelated hemodynamic, behavioral, and hippocampal deficits.
Insights
Morphine, used for pain relief, worsened sepsis symptoms in rats. This study found morphine amplified inflammation, blood pressure drops, and cognitive deficits in septic rats, highlighting potential risks of opioid use during sepsis.
Area of Science:
- Neuroscience
- Pharmacology
- Critical Care Medicine
Background:
- Sepsis and pain are common in intensive care units.
- The impact of opioid analgesics on sepsis-induced inflammation and organ damage is not fully understood.
Purpose of the Study:
- To investigate if morphine affects sepsis-induced behavioral and hippocampal damage in male rats.
- To test the hypothesis that morphine exacerbates sepsis manifestations.
Main Methods:
- Sepsis was induced using cecal ligation and puncture (CLP) in male rats.
- Animals were treated with morphine (7 mg/kg) or saline.
- Behavioral tests (Morris water maze, new object recognition) and hemodynamic measurements were performed.
- Inflammatory markers (IL-1β) and hippocampal histopathology were assessed.
- Opioid receptor blockade with naloxone was used to confirm receptor involvement.
Main Results:
- Both sepsis and morphine individually caused hypotension, cognitive deficits, and reduced exploratory behavior.
- Combined sepsis and morphine treatment significantly exaggerated these effects.
- Morphine-treated septic rats showed amplified IL-1β levels and hippocampal damage.
- Effects were dependent on intact opioid receptors, as naloxone blocked them.
Conclusions:
- Morphine intensifies sepsis-related inflammation, hemodynamic instability, and neurological deficits.
- Opioid receptors mediate morphine's detrimental effects in sepsis.
- Findings suggest caution regarding morphine use in septic patients due to potential exacerbation of symptoms.
