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Updated: Aug 11, 2026
Neurodevelopmental Reflex Testing in Neonatal Rat Pups
Published on: April 24, 2017
Development of the baroreflex in the young rat
Karen S Quigley1, Michael M Myers, Harry N Shair
1Department of Psychiatry, UMDNJ-New Jersey Medical School, Newark, NJ 07107, and East Orange VA Medical Center, War Related Illness Center, Stop #129, 385 Tremont Ave., East Orange, NJ 07018, United States. quigleks@umdnj.edu
Insights
The baroreceptor-heart period reflex in rat pups shows early development. Vasoconstriction triggers a strong reflex bradycardia by postnatal day 6, involving both vagal and sympathetic pathways in conscious pups.
Area of Science:
- Cardiovascular physiology
- Developmental biology
- Autonomic nervous system research
Background:
- The baroreceptor-heart period reflex is crucial for blood pressure regulation.
- Understanding its development in early life is vital for assessing cardiovascular health.
- Previous studies were limited to anesthetized subjects.
Purpose of the Study:
- To investigate the baroreceptor-heart period reflex in conscious, freely behaving rat pups.
- To determine the autonomic mechanisms underlying reflex responses during development.
- To compare responses between postnatal days 6 and 14.
Main Methods:
- Assessing the baroreceptor-heart period reflex using phenylephrine and sodium nitroprusside in conscious rat pups.
- Employing pharmacological autonomic blockade to identify autonomic pathways.
- Comparing responses on postnatal days 6 and 14.
Main Results:
- Vasoconstriction elicited a potent baroreflex-mediated bradycardia by postnatal day 6 in conscious pups.
- This bradycardia involved both vagal activation and sympathetic withdrawal.
- Vasodilation showed minimal autonomic response at day 6 but significant tachycardia by day 14.
Conclusions:
- The baroreceptor-heart period reflex is functional and develops rapidly in early postnatal life.
- Conscious rat pups exhibit complex autonomic adjustments in response to blood pressure changes.
- Findings highlight the importance of studying autonomic function in awake, behaving animals for accurate developmental insights.
Abstract:
The baroreceptor-heart period reflex was assessed in conscious, freely behaving rat pups on postnatal days 6 and 14. The baroreceptor-heart period reflex was elicited using the alpha1-adrenergic agonist phenylephrine to increase blood pressure and the vasodilator, sodium nitroprusside, to decrease blood pressure. The autonomic effects of the baroreceptor manipulations were determined using pharmacological autonomic blockade. The data demonstrate that vasoconstriction produces a potent baroreflex-mediated bradycardia as early as postnatal day 6, which had previously been demonstrated only in anesthetized pups. In the anesthetized pup, the bradycardia is mediated by vagal activation, while we demonstrate that both vagal activation and sympathetic withdrawal occur in unanesthetized animals. In addition, the results replicate previous findings in rats demonstrating minimal cardiac sympathetic activation or vagal withdrawal following vasodilation during the first week of life, but substantial baroreflex-mediated tachycardia by the second week.
