The goal of this study was to build on the historic use of the avian model of development and also to further the knowledge of autonomic nervous system (ANS) regulation of cardiovascular function in vertebrates. Vasoactive drugs sodium nitroprusside, a vasodilator and phenylephrine, a vasoconstrictor were used to study the correlation of cardiovascular function relationship with nerve activity, both sympathetic and parasympathetic (vagal). Additionally, ANG II was used to assess its effects on vagal inhibition. The present study shows that pharmacologically-induced hypertension is associated with a fall in mSNA, indicating that the capacity for sympathetic autonomic cardiovascular regulation is established by late incubation however, late-stage embryonic chickens did not show a significant increase in mSNA during hypotension. The hypotensive response of the embryo was not accompanied by the expected inhibition of vagal discharge; however a slight but insignificant reduction in vagal discharge was noted. When vagal efferent output was isolated, a significant drop in vagal efferent activity was noted in response to hypotension. The present study showed late-stage embryonic chickens lack a vagal response to hypertension in both efferent and sensory limbs. In this study, vagal discharge was reduced from baseline levels in response to Ang II. Collectively, the present study indicates that the lack of a decreased heart rate, in response to increases in Pm caused by Ang II, is due to a central inhibitory action of Ang II on the vagus. Data from the present study suggests that although autonomic interaction with the cardiovascular system in present in late-stage chicken embryos, it is still underdeveloped and possesses a limited capacity.
| Identifer | oai:union.ndltd.org:unt.edu/info:ark/67531/metadc1404516 |
| Date | 12 1900 |
| Creators | Onyemaechi, Clinton |
| Contributors | Crossley, Dane, Hedrick, Michael, Dzialowski, Edward |
| Publisher | University of North Texas |
| Source Sets | University of North Texas |
| Language | English |
| Detected Language | English |
| Type | Thesis or Dissertation |
| Format | x, 55 pages, Text |
| Rights | Public, Onyemaechi, Clinton, Copyright, Copyright is held by the author, unless otherwise noted. All rights Reserved. |
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