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The effect of hyperthyroidism on opiate receptor binding and pain sensitivity
E A Edmondson1, K A Bonnet, A J Friedhoff
1Baylor College of Medicine, Houston, Texas 77030.
Life Sciences
|January 1, 1990
Summary
Thyroid hormone (thyroxine) increases opiate receptor numbers and pain sensitivity in mice. However, hyperthyroid mice experience shorter pain relief from morphine, indicating altered opioid efficacy.
Area of Science:
- Endocrinology
- Neuroscience
- Pharmacology
Background:
- Thyroid hormones play a crucial role in regulating various physiological processes.
- Opiate receptors are key targets for pain modulation and analgesia.
Purpose of the Study:
- To investigate the impact of thyroid hormone on opiate receptor ligand-binding.
- To assess the effect of thyroid hormone on pain sensitivity and opioid analgesia.
Main Methods:
- Opiate receptor binding assays using 3H-naloxone on mouse brain homogenates.
- Scatchard analysis to determine receptor number (Bmax) and binding affinity (Kd).
- Hotplate test to evaluate pain sensitivity and analgesia duration after morphine administration.
Main Results:
- Hyperthyroid mice showed significantly increased 3H-naloxone binding, indicating more opiate receptors (higher Bmax).
- Binding affinity (Kd) for opiate receptors remained unchanged between hyperthyroid and control groups.
- Hyperthyroid mice exhibited heightened pain sensitivity and a reduced duration of morphine-induced analgesia.
Conclusions:
- Thyroxine administration upregulates the number of opiate receptors in the brain.
- Hyperthyroidism enhances endogenous pain sensitivity and diminishes the effectiveness of exogenous opioids like morphine.