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We determined heart rate ( f<jats:sub>H<\/jats:sub>) and mean arterial pressure (P<jats:sub>m<\/jats:sub>) in acute normoxic (21% O<jats:sub>2<\/jats:sub>) and acute hypoxic (10% O<jats:sub>2<\/jats:sub>) conditions, as well as embryonic responses to cholinergic, adrenergic, and ganglionic pharmacological blockade. Compared with N21 embryos, chronic H10 embryos had smaller bodies and relatively larger hearts and were hypotensive, tachycardic, and following autonomic neural blockade showed reduced intrinsic f<jats:sub>H<\/jats:sub> at 90% of incubation. Unlike other reptile embryos, cholinergic and ganglionic receptor blockade both increased f<jats:sub>H<\/jats:sub>. \u03b2-Adrenergic receptor blockade with propranolol decreased f<jats:sub>H<\/jats:sub>, and \u03b1-adrenergic blockade with phentolamine decreased P<jats:sub>m<\/jats:sub>. We also measured cardiac mRNA expression. Cholinergic tone was reduced in H10 embryos, but cholinergic receptor ( Chrm2) mRNA levels were unchanged. However, expression of adrenergic receptor mRNA ( Adrb1, Adra1a, Adra2c) and growth factor mRNA ( Igf1, Igf2, Igf2r, Pdgfb) was lowered in H10 embryos. Hypoxia altered the balance between cholinergic receptors, \u03b1-adrenoreceptor and \u03b2-adrenoreceptor function, which was reflected in altered intrinsic f<jats:sub>H<\/jats:sub> and adrenergic receptor mRNA levels. This is the first study to link gene expression with morphological and cardioregulatory plasticity in a developing reptile embryo. <\/jats:p>","DOI":"10.1152\/ajpregu.00595.2012","type":"journal-article","created":{"date-parts":[[2013,4,4]],"date-time":"2013-04-04T06:37:48Z","timestamp":1365057468000},"page":"R966-R979","source":"Crossref","is-referenced-by-count":36,"title":["Plasticity of cardiovascular function in snapping turtle embryos (<i>Chelydra serpentina<\/i>): chronic hypoxia alters autonomic regulation and gene expression"],"prefix":"10.1152","volume":"304","author":[{"given":"John","family":"Eme","sequence":"first","affiliation":[{"name":"Department of Biological Sciences, University of North Texas, Denton, Texas;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Turk","family":"Rhen","sequence":"additional","affiliation":[{"name":"Department of Biology, University of North Dakota, Grand Forks, North Dakota; 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