Abstract
Model organisms are commonly used to investigate and characterize the physiology of embryonic and fetal vertebrates. The embryonic chicken has been used extensively to study the physiology of the developing cardiovascular system in vertebrates. Using this model general patterns of cardiovascular development have been thoroughly characterized in the avian embryo. However, given the differences in morphology, total incubation length and neonatal maturity found across avian species, the specific patterns of cardiovascular development established in a chicken strain may not apply universally to avian embryos. In fact, recent studies have demonstrated that aspects of cardiovascular regulation in embryonic chickens may be strain specific. Thus, we predicted that two chicken strains, the red jungle fowl and the black Sumatran bantam chicken, would exhibit different patterns of cardiovascular function and regulation during development. The red jungle fowl was selected as is represents the strain that domestic chickens are derived from and the Sumatran chicken was selected as one of the strains that were derived from the red jungle fowl. When measured on the same days of incubation, arterial pressure was lower in the Sumatran embryo compared to the red jungle fowl, while heart rate was similar between the strains. Cholinergic receptor tone on heart rate increased in strength over the study period and was present on day 13 of incubation in the Sumatran embryos while its function was delayed until day 17 of red jungle fowl incubation. Finally, both strains showed β adrenergic tone on heart rate on all days of incubation studied and α adrenergic tone on arterial pressure on day 19. Collectively our data suggest that timing of functional cholinergic tone on heart rate is strain dependent, while beta adrenergic tone on heart rate was functional on similar days of incubation.