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Changes in alpha 1-adrenoceptor coupling to Ca2+ channels during development in rat heart
Q Y Liu1, E Karpinski, P K Pang
1Department of Physiology, University of Alberta, Edmonton, Canada.
FEBS Letters
|January 31, 1994
Summary
Alpha-1 adrenoceptor activation affects calcium (Ca2+) currents differently in developing rat hearts. Neonatal rat myocytes show increased Ca2+ current, unlike adult myocytes, indicating a developmental switch in receptor coupling.
Area of Science:
- Cardiology
- Molecular Pharmacology
- Developmental Biology
Background:
- Alpha-1 adrenoceptor activation in adult rat hearts influences cardiac function, potentially via effects on calcium (Ca2+) currents.
- Previous studies suggest alpha-1 adrenoceptor activation in adult rat hearts decreases I(t) rather than increasing Ca2+ current, contributing to positive inotropy.
Purpose of the Study:
- To investigate the developmental changes in the effect of alpha-1 adrenoceptor activation on L-type Ca2+ channel current in rat myocytes.
- To compare the response of neonatal and young adult rat myocytes to phenylephrine, an alpha-adrenergic agonist.
Main Methods:
- Patch-clamp electrophysiology was used to measure L-type Ca2+ channel current.
- Myocytes were isolated from neonatal and young adult rats.
- The effects of phenylephrine, an alpha-1 adrenergic agonist, were examined in the presence of propranolol (a beta-blocker) and prazosin (an alpha-1 antagonist).
Main Results:
- Phenylephrine significantly increased the L-type Ca2+ channel current in neonatal rat myocytes.
- This effect was reversed by prazosin, confirming alpha-1 adrenoceptor mediation.
- In contrast, phenylephrine did not significantly alter the L-type Ca2+ channel current in young adult rat myocytes.
Conclusions:
- The coupling of alpha-1 adrenoceptors to L-type Ca2+ channels changes during cardiac development.
- This developmental switch may underlie the differential effects of alpha-1 adrenergic stimulation on cardiac function in neonatal versus adult rats.