Neuropeptide Y is an essential in vivo developmental regulator of cardiac ICa,L.
Cell culture studies demonstrate an increase in cardiac L-type Ca2+ current (ICa,L) density on sympathetic innervation in vitro and suggest the effect depends on neurally released neuropeptide Y (NPY). To determine if a similar mechanism contributes to the postnatal increase in ICa,L in vivo, we prepared isolated ventricular myocytes from neonatal and adult mice with targeted deletion of the NPY gene (Npy-/-) and matched controls (Npy+/+). Whole-cell voltage clamp demonstrates ICa,L density increases postnatally in Npy+/+ (by 56%), but is unchanged in Npy-/-. Both ICa,L density and action potential duration are significantly greater in adult Npy+/+ than Npy-/- myocytes, whereas ICa,L density is equivalent in neonatal Npy+/+ and Npy-/- myocytes. These data indicate NPY does not influence ICa,L prenatally, but the postnatal increase in ICa,L density is entirely NPY-dependent. In contrast, there is a similar postnatal negative voltage shift in the I-V relation in Npy+/+ and Npy-/-, indicating NPY does not influence the developmental change in ICa,L voltage-dependence. Immunoblot analyses and measurements of maximally activated ICa,L (in presence of forskolin or BayK 8644) show that the differences in current density between Npy+/+ and Npy-/- cannot be attributed to altered Ca2+ channel alpha1C subunit protein expression. Rather, these results suggest that the in vivo NPY-dependent postnatal increase in ICa,L density in cardiac myocytes results from regulation ICa,L properties by NPY.
Protas
Lev
L
Department of Pharmacology, Columbia University, 630 W 168th St, New York, NY 10032, USA.
Barbuti
Andrea
A
Qu
Jihong
J
Rybin
Vitalyi O
VO
Palmiter
Richard D
RD
Steinberg
Susan F
SF
Robinson
Richard B
RB
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D002120:Calcium Channel Agonists / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D002469:Cell Separation; D005576:Colforsin / Q000494:pharmacology; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D006352:Heart Ventricles / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009478:Neuropeptide Y / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D018408:Patch-Clamp Techniques
D002120:Calcium Channel Agonists; D020746:Calcium Channels, L-Type; C419385:L-type calcium channel alpha(1C); D009478:Neuropeptide Y; D005576:Colforsin; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester