Letter Regarding Article by Okoshi et al, “Neuregulins Regulate Cardiac Parasympathetic Activity: Muscarinic Modulation of β-Adrenergic Activity in Myocytes From Mice With Neuregulin-1 Gene Deletion”

Abstract

To the Editor: Okoshi and colleagues1 studied the modulatory role of neuregulin-1 on parasympathetic activity in the heart. This interesting study on isolated cardiomyocytes showed that heterozygous gene deletion of neuregulin-1 abrogated the inhibitory activity of the muscarinic cholinergic system on β-adrenergic signaling. Because protein levels of M2 muscarinic receptors and G protein subunits were unchanged in neuregulin-1–deficient cardiomyocytes, the authors proposed that neuregulins support normal parasympathetic modulation of excess β-adrenergic stimulation of the heart. In a recent article in Circulation ,2 we reported that exogenously administrated neuregulin-1 attenuated β-adrenergic responses of isolated papillary muscles in the absence …