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This Article Full Text Full Text (PDF) Supplemental data All Versions of this Article: 585/1/175    most recent jphysiol.2007.138180v1 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 HighWire Citing Articles via Google Scholar Google Scholar Articles by Oku, Y. Articles by Okada, Y. Search for Related Content PubMed PubMed Citation Articles by Oku, Y. Articles by Okada, Y. Related Collections Respiratory

¹ Department of Physiology, Hyogo College of Medicine, Hyogo 663-8501, Japan
² Department of Medicine, Keio University Tsukigase Rehabilitation Center, Shizuoka 410-3215, Japan

Two putative respiratory rhythm generators (RRGs), the para-facial respiratory group (pFRG) and the pre-Bötzinger complex (preBötC), have been identified in the neonatal rodent brainstem. To elucidate their functional roles during the neonatal period, we evaluated developmental changes of these RRGs by optical imaging using a voltage-sensitive dye. Optical signals, recorded from the ventral medulla of brainstem–spinal cord preparations of neonatal (P0–P4) rats (n = 44), were analysed by a cross correlation method. With development during the first few postnatal days, the respiratory-related activity in the pFRG reduced and shifted from a preinspiratory (P0–P1) to an inspiratory (P2–P4) pattern, whereas preBötC activity remained unchanged. The µ-opioid agonist [D-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO) augmented preinspiratory activity in the pFRG, while the µ-opioid antagonist naloxone induced changes in spatiotemporal activation profiles that closely mimicked the developmental changes. These results are consistent with the recently proposed hypothesis by Janczewski and Feldman that the pFRG is activated to compensate for the depression of the preBötC by perinatal opiate surge. We conclude that significant reorganization of the respiratory neuronal network, characterized by a reduction of preinspiratory activity in the pFRG, occurs at P1–P2 in rats. The changes in spatiotemporal activation profiles of the pFRG neurones may reflect changes in the mode of coupling of the two respiratory rhythm generators.

(Received 7 June 2007; accepted after revision 20 September 2007; first published online 20 September 2007)
Corresponding author Y. Oku: Department of Physiology, Hyogo College of Medicine, Nishinomiya, Hyogo 663-8501, Japan. Email: yoku{at}hyo-med.ac.jp

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