Key result
Acetylcholine reduced the efficacy of isoprenaline and the potency of forskolin to stimulate calcium currents in frog ventricular myocytes, while low concentrations of both acted synergistically.
In frog ventricular myocytes, acetylcholine inhibits calcium currents stimulated by isoprenaline primarily by reducing efficacy, and inhibits those stimulated by forskolin primarily by reducing potency.
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May inform cAMP-ICa modulation mechanisms; leaves open relevance to mammalian physiology.
Fischmeister et al. (1989) studied this question. Isoprenaline, forskolin, and acetylcholine vs. Control was evaluated on Calcium currents (ICa) EC50 and Emax. Acetylcholine reduced the efficacy of isoprenaline and the potency of forskolin to stimulate calcium currents in frog ventricular myocytes, while low concentrations of both acted synergistically.
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