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First published online January 5, 2005
Journal of Experimental Biology 208, 213-222 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01399

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Development of the respiratory response to hypoxia in the isolated brainstem of the bullfrog Rana catesbeiana

Rachel E. Winmill, Anna K. Chen and Michael S. Hedrick^*

Department of Biological Sciences, California State University, Hayward, Hayward, CA 94542, USA

View larger version (29K): [in a new window]   Fig. 1. Effects of 2 h hypoxia on respiratory-related neural activity from pre-metamorphic, post-metamorphic and adult brainstems. Raw (V) and integrated (V) activity recorded from the trigeminal cranial nerve (CN V) preparations from (A) stage XIV pre-metamorphic tadpole, (B) stage XXIV post-metamorphic tadpole and (C) adult brainstem during control conditions, 10 min and 120 min hypoxia, and recovery. Fictive gill and lung burst activity are present in the pre-metamorphic tadpole after 2 h, but neural activity ceased in the post-metamorphic and adult preparations. An example of a single non-respiratory burst is shown for the post-metamorphic brainstem during hypoxia.

View larger version (20K): [in a new window]   Fig. 2. Summary of effects of hypoxia on burst frequency in (A) fictive gill (open circles) and lung (solid circles) in pre-metamorphic tadpoles and (B) on lung burst frequency in the post-metamorphic tadpole (open circles), and adult (solid circles). *P<0.05 compared with control values.

View larger version (21K): [in a new window]   Fig. 3. Effects of hypoxia (open circles) and hypoxia + iodoacetate (solid circles) in aCSF on gill/lung burst frequencies in tadpole and adult brainstems. (A) pre-metamorphic tadpole gill cranial nerves frequency; (B) pre-metamorphic lung burst frequency; (C) adult lung burst frequency. *P<0.05 compared with control values.

View larger version (10K): [in a new window]   Fig. 4. An expanded trace illustrating typical respiratory-related bursts in the pre-metamorphic tadpole, postmetamorphic tadpole and adult during control conditions and hypoxia. Note there is no change in individual burst characteristics, including amplitude, duration or rise time at any developmental stage.

View larger version (23K): [in a new window]   Fig. 5. Summary of effects of hypoxia on (A) lung burst episode frequency and (B) number of lung bursts per episode in pre-metamorphic tadpole (white bars), post-metamorphic tadpole (black bars) and adult (hatched bars) brainstems. Data for post-metamorphic tadpole and adult preparations were obtained during the initial 5–15 min exposure to hypoxia, prior to the respiratory cessation that occurred in these preparations (see text). *P<0.05 compared with control values.

View larger version (21K): [in a new window]   Fig. 6. Summary of effects of hypoxia on frequency of non-respiratory bursts in pre-metamorphic (white bars), post-metamorphic (black bars) and adult (hatched bars) brainstems. Non-respiratory bursts in post-metamorphic and adult preparations were obtained during the initial 5–15 min of hypoxia. *P<0.05 compared with control values.