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This Article Full Text Full Text (PDF) Supplemental data All Versions of this Article: 584/2/489    most recent jphysiol.2007.142760v1 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 Ruangkittisakul, A. Articles by Ballanyi, K. Search for Related Content PubMed PubMed Citation Articles by Ruangkittisakul, A. Articles by Ballanyi, K. Related Collections Neuroscience

¹ Department of Physiology and Perinatal Research Centre, University of Alberta, Edmonton, Alberta, Canada T6G 2S2

The pre-Bötzinger Complex (preBötC) inspiratory centre remains active in isolated brainstem–spinal cords and brainstem slices. The extent to which findings in these models depend on their dimensions or superfusate [K⁺] and [Ca²⁺] (both of which determine neuronal excitability) is not clear. We report here that inspiratory-related rhythms in newborn rat slices and brainstem–spinal cords with defined boundaries were basically similar in physiological Ca²⁺ (1.2 mM) and K⁺ (3 mM). Hypoglossal nerve rhythm was 1 : 1-coupled to preBötC activity in slices and to cervical nerve bursts in en bloc preparations lacking the facial motonucleus (VII). Hypoglossal rhythm was depressed in brainstems containing (portions of) VII, while pre/postinspiratory lumbar nerve bursting was present only in preparations with > 79% VII. preBötC-related slice rhythms were inhibited in 1.5 mM Ca²⁺ solution, whereas their longevity and burst rate were substantially augmented in 1 mM Ca²⁺. Ca²⁺ depression of slice rhythms was antagonized by raising superfusate K⁺ to 8–10 mM. This strong extracellular Ca²⁺/K⁺ antagonism of inspiratory (motor) rhythms was also revealed in brainstem–spinal cords without VII, while the inhibition was progressively attenuated with increasing amount of rostral tissue. We hypothesize that depression of hypoglossal rhythm and decreased Ca²⁺ sensitivity of preBötC rhythm are probably not related to an increased content of rostral respiratory structures, but rather to larger brainstem dimensions resulting in interstitial gradients for neuromodulator(s) and K⁺, respectively. We discuss whether block of pre/postinspiratory activity in preparations with < 79% VII is due to impairment of the pathway from preinspiratory interneurons to abdominal muscles

(Received 9 August 2007; accepted after revision 18 August 2007; first published online 23 August 2007)
Corresponding author K. Ballanyi: Department of Physiology and Perinatal Research Centre, 220 HMRC, University of Alberta, Edmonton, Alberta, Canada T6G 2S2. Email: klaus.ballanyi{at}ualberta.ca

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