January 23, 2025Journal of Cardiovascular Pharmacology
Chronotropic Effects of Milrinone in a Guinea Pig Ex Vivo Model: A Pilot Study to Screen for New Mechanisms of Action
Key result
Carvedilol reduces milrinone-induced chronotropy by ~60% in guinea pig atria, suggesting 5-HT receptor dependence.
- P<0.01
Why the study?
It was unclear whether the positive chronotropic effect of milrinone is evoked solely by PDE inhibition or through additional pharmacological targets.
Does milrinone evoke positive chronotropic responses solely by PDE inhibition or through additional pharmacological targets in guinea pig right atrial preparations?
Population
Right atrial preparations of guinea pig
Comparison
Milrinone with vs without inhibitors of putative ancillary molecular pathways or ion channels
Design
Ex vivo pilot study
Authors
Discussion
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Implication
May indicate off-target chronotropic effects of milrinone; leaves open translation to human physiology or practice.
Structured PICO
Does milrinone evoke positive chronotropic responses solely by PDE inhibition or through additional pharmacological targets in guinea pig right atrial preparations?
P
Population
Right atrial preparations of guinea pig ex vivo model
I
Intervention
Milrinone combined with various inhibitors (carvedilol, propranolol, metoprolol, prazosin, apamin, verapamil, diltiazem, lidocaine, tetrodotoxin, quinidine)
C
Comparator
Milrinone alone
O
Outcome
Milrinone-stimulated increases in heart rate (positive chronotropy)surrogate
Main Result
p-value: p=< 0.01
Milrinone's positive chronotropic effect may involve a 5-HT receptor-dependent component in addition to PDE inhibition.
Limitations
- Exploratory approach requiring more focused experiments with selective 5-HT receptor antagonists to confirm the specific pathway.
- Exploratory approach requiring confirmation with selective 5-HT receptor antagonists
Cite This Study
Pollesello et al. (2025) studied Ex vivo guinea pig model. Milrinone with various inhibitors (e.g., carvedilol, propranolol, metoprolol) vs. Milrinone alone was evaluated on Milrinone-stimulated increases in heart rate (p=< 0.01). Carvedilol limited the positive chronotropic effects of milrinone to about 40% (P<0.01) in guinea pig right atrial preparations, suggesting a potential 5-HT receptor-dependent component.