title: Changes in baroreceptor vagal reflex performance in the developing rat.
abstract: Ontogenesis of both vagal control of heart rate and the baroreceptor vagal reflex were evaluated in rats at postnatal ages (P) of 5/6, 10, 15, 20, 25 and >>42 days anaesthetised with urethane (1.5 g/kg). Between P5/6 and P25 heart rate rose from 372 +/- 12 to 448 +/- 20 beats per minute and mean arterial pressure increased from 33.9 +/- 3.1 to 74.59 +/- 3.25 mm Hg (mean +/- SEM, n = 7 and 11 respectively). Cardiac vagal tone was absent at P10 but significant at P20 (P < 0.05) as revealed with atropine (0.5-1 mg/kg i.v.). Baroreceptor cardiac reflex sensitivity, tested with phenylephrine (10-50 microg/kg i.v.), was attenuated significantly in P10-20 rats compared with P5/6, P25 and mature animals. In P14-17 rats stimulation of neurones in either the solitary tract or ambiguual nuclei, by microinjection of L-glutamate (100-200 pmol), evoked an atropine-sensitive bradycardia indicating a functional integrity of central and peripheral efferent pathways mediating the baroreceptor reflex. Thus, the baroreceptor vagal reflex is functional in P5/6 rats but becomes attenuated between P10-P20, which is coincident with the maturational rise in arterial pressure.
authors.affiliation: Department of Physiology, School of Medical Sciences, University of Bristol, Bristol, BS8 1TD, UK.
authors.forename: S
authors.initials: S
authors.lastname: Kasparov
authors.forename: J F
authors.initials: JF
authors.lastname: Paton
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development*; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure; D002628:Chemoreceptor Cells / Q000502:physiology; D005260:Female; D018698:Glutamic Acid / Q000494:pharmacology; D006329:Heart Conduction System / Q000254:growth & development / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology; D008845:Microinjections; D051381:Rats; D017207:Rats, Sprague-Dawley; D012018:Reflex / Q000502:physiology; D017552:Solitary Nucleus / Q000502:physiology; D013564:Sympathetic Nervous System / Q000254:growth & development / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology*
chemical_list: D018698:Glutamic Acid