Mechanism of Action of Morphine
Morphine exerts its therapeutic effects through its interaction with opioid receptors, primarily the mu-opioid receptor. These receptors are distributed throughout the central and peripheral nervous systems and play a key role in modulating pain signals.
When morphine binds to mu-opioid receptors, it inhibits the release of neurotransmitters involved in pain transmission, such as substance P and glutamate. This action reduces neuronal excitability and diminishes the sensation of pain at both spinal and supraspinal levels.
Additionally, morphine activates descending inhibitory pathways that further suppress pain signaling. These combined effects result in potent analgesia. Morphine also influences brain regions associated with emotional responses, contributing to its calming and sedative properties.
Beyond analgesia, morphine affects respiratory centers in the brainstem, which can lead to respiratory depression at high doses. This effect underscores the importance of careful dosing and patient monitoring, especially in opioid-naïve individuals.
Understanding morphine’s mechanism of action has informed safer prescribing practices and guided the development of opioid antagonists and supportive treatments.