title: Developmental changes in functional characteristics of aortic baroreceptor afferents in rats.
abstract: To investigate postnatal developmental changes in functional characteristics of the afferent pathway of the aortic baroreceptor reflex, the responses of aortic nerve activity (ANA) to blood pressure (BP) changes elicited by phenylephrine and sodium nitroprusside administration were tested in 3-, 8- and 20-week-old male rats under chloralose (60 mg kg(-1) i.p.) and urethane (600 mg kg(-1) i.p.) anaesthesia. The function curve of ANA in response to BP changes showed a sigmoid shape that shifted to the right from 3 to 8 weeks of age. The maximal activity and maximal gain of the aortic nerve, which were calculated by a logistic function analysis, were significantly higher in 20-week-old rats (maximal activity, 532 +/- 47% of baseline; maximal gain, 7.9 +/- 0.8% of baseline mmHg(-1); n = 9) than in 3-week-old rats (maximal ANA, 268 +/- 25% of baseline, P < 0.001; maximal gain, 4.9 +/- 0.5% of baseline mmHg(-1), P < 0.01, n = 9) and 8-week-old rats (maximal ANA, 309 +/- 18% of baseline, P < 0.001; maximal gain, 4.9 +/- 0.3% of baseline mmHg(-1), P < 0.01, n = 11). These results suggest that the operating point of aortic baroreceptor afferents is reset to the higher pressure level during development from 3 to 8 weeks of age and, thereafter, the afferent gain increases from 8 to 20 weeks of age. This functional change may be an important factor to prevent an excess increase of BP, which would result in pathophysiological problems.
authors.affiliation: Department of Physiology-II, Wakayama Medical University School of Medicine, 811-1 Kimiidera, Wakayama City, Japan. h-waki@wakayama-med.ac.jp
authors.forename: Hidefumi
authors.initials: H
authors.lastname: Waki
authors.forename: Masao
authors.initials: M
authors.lastname: Yamasaki
authors.forename: Kiyoaki
authors.initials: K
authors.lastname: Katahira
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Katsuda
authors.forename: Masanobu
authors.initials: M
authors.lastname: Maeda
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Shimizu
mesh_terms: D000200:Action Potentials; D000222:Adaptation, Physiological; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001011:Aorta / Q000187:drug effects / Q000294:innervation*; D017704:Baroreflex / Q000187:drug effects; D001794:Blood Pressure; D008297:Male; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D009599:Nitroprusside / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011311:Pressoreceptors / Q000187:drug effects / Q000254:growth & development*; D051381:Rats; D017207:Rats, Sprague-Dawley; D046468:Sexual Development; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009599:Nitroprusside; D010656:Phenylephrine