Development of the baroreflex in the young rat.
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.
Quigley
Karen S
KS
Department 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
Myers
Michael M
MM
Shair
Harry N
HN
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001262:Atenolol / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D001341:Autonomic Nervous System / Q000187:drug effects / Q000254:growth & development; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004569:Electroencephalography / Q000379:methods; D006321:Heart / Q000187:drug effects / Q000254:growth & development* / Q000502:physiology; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D000319:Adrenergic beta-Antagonists; D018727:Muscarinic Antagonists; D014665:Vasodilator Agents; D009599:Nitroprusside; D010656:Phenylephrine; D001262:Atenolol; D001285:Atropine