Leu-enkephalin increased heart rate in isolated hypertensive rat atria but not in normal rat atria across all ages tested, revealing altered cardiac opioid function in hypertension.
SHR-specific effectLeu-enkephalin increased heart rate in hypertensive atria across all ages while having no effect in normal hearts
What the researchers found
Leu-enkephalin at 0.2 micromolar increased spontaneous beating rate in SHR atria but not in normal rat atria, across ages 4 to 16 weeks.
Why it matters
If opioid receptors work differently in hypertensive hearts, this could reveal new targets for blood pressure or heart rate treatments.
How the study worked
Researchers isolated right atria from hypertensive and normal rats at ages 4, 8, 12, and 16 weeks. They applied opioid peptides (beta-endorphin, dynorphin, met-enkephalin, DAGO, DADLE, leu-enkephalin) and measured spontaneous beating rate changes.
What this study cannot tell us
Animal study using isolated rat heart tissue. The in vitro setting does not capture the full complexity of how opioid peptides work in a living animal. Only tested a narrow range of concentrations.
How to read the evidence
Preliminary — in vitro study using isolated rat atria from three strains. Consistent across ages but mechanism not identified.
When this study was published
Published in 1993 (33 years ago). Cardiac opioid receptor changes in hypertension remain of clinical interest.
The bigger picture
Hypertension changes how the heart responds to opioid peptides. This could contribute to cardiac complications in hypertension and suggests new therapeutic approaches.
Questions still open
- What receptor mechanism causes leu-enkephalin to increase rate only in hypertensive hearts?
- Could this altered opioid response contribute to arrhythmias in hypertension?
Common questions
Why does leu-enkephalin act differently in hypertensive hearts?
Could this affect hypertensive patients on opioid drugs?
Read the original research
Possible opioid receptor function changes in isolated atria of the spontaneously hypertensive rat.
General pharmacology, 24(6), 1483-90
Citation
Wong, S C; Ingenito, A J. (1993). Possible opioid receptor function changes in isolated atria of the spontaneously hypertensive rat.. General pharmacology, 24(6), 1483-90.