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This Article Full Text Full Text (PDF) All Versions of this Article: 93/3/319    most recent expphysiol.2007.039362v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Waki, H. Articles by Shimizu, T. Search for Related Content PubMed PubMed Citation Articles by Waki, H. Articles by Shimizu, T.

¹ Department of Physiology - II, Wakayama Medical University School of Medicine, 811-1 Kimiidera, Wakayama 641-8509, Japan ² Department of Physiology ³ Experimental Animal Center, Fukushima Medical University, 1 Hikari-ga-oka, Fukushima 960-1247, Japan

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.

(Received 5 July 2007; accepted after revision 25 October 2007; first published online 26 October 2007)
Corresponding author H. Waki: Department of Physiology – II, Wakayama Medical University School of Medicine, 811-1, Kimiidera, Wakayama City, 641-8509, Japan. Email: h-waki{at}wakayama-med.ac.jp