Related Experiment Video
Updated: Aug 10, 2026
07:23
Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
Published on: July 29, 2014
Inescapable shock-induced potentiation of morphine analgesia
L C Sutton1, S E Lea, M J Will
1Department of Psychology, University of Colorado, Boulder 80309-0345, USA.
Behavioral Neuroscience
|February 12, 1998
Summary
Stress potentiates morphine analgesia, particularly after inescapable shock (IS). This effect, observed 24–48 hours post-stress, highlights the impact of prior stress exposure on opiate pain relief.
Area of Science:
- Neuroscience
- Pharmacology
- Behavioral Science
Background:
- Stress exposure can alter pain perception and response to analgesics.
- The potentiation of morphine's effects by stressors is not well understood.
- Understanding these interactions is crucial for pain management and opiate action.
Purpose of the Study:
- To investigate how inescapable shock (IS) influences morphine analgesia.
- To characterize the time course of IS-induced potentiation of morphine's analgesic effects.
- To differentiate stress-induced potentiation from other physiological changes.
Main Methods:
- Rats were subjected to inescapable shock (IS), escapable shock (ES), or restraint (control).
- Morphine analgesia was assessed using the tail-flick (TF) test and hotplate test at 24 and 48 hours post-stress.
- Control measures included monitoring tail temperature and motor function.
Main Results:
- Inescapable shock (IS) significantly potentiated morphine analgesia at 24 and 48 hours.
- Escapable shock (ES) and restraint did not produce similar potentiation effects.
- No significant changes in tail temperature or motor activity were observed that could account for the enhanced analgesia.
Conclusions:
- Prior exposure to inescapable shock enhances morphine analgesia in a time-dependent manner.
- These findings align with learned-helplessness paradigms and suggest specific neural mechanisms.
- The results have implications for understanding stress-related modulation of pain and opiate efficacy.
Related Concept Videos
01:20Desensitization and Tachyphylaxis
Tachyphylaxis is described as a rapid decrease in response to a drug after repeated or continuous administration of the same drug dose. It is a phenomenon where the body becomes less responsive to a particular substance or intervention over time, requiring higher doses or stronger interventions to achieve the same effect. It results from adaptive changes in the body's receptors, signaling pathways, or physiological processes that occur in response to prolonged exposure to a stimulus.
Several...
Several...
01:22Opioid Receptors: Overview
Opioid receptors, including the mu (μ, MOR), delta (δ, DOR), and kappa (κ, KOR) types, belong to the rhodopsin family of G protein-coupled receptors. These receptors are located throughout the central and peripheral nervous systems and in non-neuronal tissues such as macrophages and astrocytes. Opioid receptor ligands can be categorized into agonists or antagonists. Highly selective agonists include [d-Ala2, MePhe4, Gly(ol)5]-enkephalin or DAMGO for MOR, [D-Pen2, D-Pen5]-enkephalin or DPDPE for...
01:25Analgesia and Pain Management
Pain is critical to various clinical pathologies, provoking an urgent need for effective management. Pain, whether acute or chronic, is a complex neurochemical process. Its alleviation depends on the type, with nonopioid analgesics effective for mild to moderate pain, such as musculoskeletal or inflammatory pain, while neuropathic pain responds best to anticonvulsants, tricyclic antidepressants, or serotonin/norepinephrine reuptake inhibitors. For severe acute or chronic pain, opioids may be...
01:20Opioid Analgesics: Morphine and Other Natural Cogeners
Opioids are a class of drugs that mimic endogenous opioid peptides and act on opioid receptors, and help in pain relief. These compounds are classified as natural, synthetic, or semi-synthetic. Natural opioids, like morphine, codeine, and thebaine, are derived from the opium poppy plant (Papaver somniferum or Papaver album) and are termed opiates. Synthetic opioids are artificial, while semi-synthetic opioids combine natural and synthetic compounds. Morphine, a prototypical opioid, possesses a...
01:15Opioid Analgesics: Synthetic and Semisynthetic Opioids
Synthetic and semisynthetic opioids are pivotal in pain management and tackling opioid addiction. Semisynthetic opioids, including morphinans (morphine derivatives), oxycodone, oxymorphone, hydrocodone, and hydromorphone, have improved pharmacokinetic profiles compared to morphine. Additionally, heroin and 6-MAM (6-Monoacetylmorphine) show better CNS penetration than morphine due to heightened lipid solubility. Hydromorphone, a potent opioid, undergoes hepatic metabolism to form the active...
01:17Drugs Affecting GI Tract Motility: Opioids as Antidiarrheal Agents
Diarrhea, a condition marked by frequent loose or watery bowel movements, can be triggered by multiple factors such as viral or bacterial infections, food intolerances, anxiety, medications, and digestive disorders. Symptoms may include abdominal pain, bloating, nausea, and cramping. Severe or prolonged diarrhea can lead to complications like electrolyte imbalances, malnutrition, and dehydration if left untreated.
Opioids, widely used antidiarrheal agents, mitigate diarrhea by slowing down...
Opioids, widely used antidiarrheal agents, mitigate diarrhea by slowing down...