Extracellular calcium induces quiescence of the low-frequency embryonic motor rhythm in the mouse isolated brainstem
✍ Scribed by A. Meillerais; J. Champagnat; M.P. Morin-Surun
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 928 KB
- Volume
- 88
- Category
- Article
- ISSN
- 0360-4012
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✦ Synopsis
Although extracellular calcium ionic concentration ([Ca] o ) is known to increase during late gestation and to drop after parturition, little is known about the influence of [Ca] o on fetal brain function. We have investigated the influence of [Ca] o , calcium-sensing receptors/nonselective cation currents (CaSR/NSCC), and GABAergic inhibitions on maturation of brainstem-spinal motor activities: the primary low-frequency embryonic rhythm [LF; silent since embryonic day (E)16] and the fetal respiratory rhythm (RR; emerging at E14-E15). Using in vitro isolated brainstem-spinal cord preparations of mice at different fetal and postnatal (P) stages (E16-P1), we demonstrate that reducing fetal [Ca] o from 1.2 mM to 0.7 mM at E16-E18 or blocking GABA A receptors at E16-P0 reactivates LF and reveals LF-related disturbance of RR at E16-E18. This LF is stopped by adding gadolinium or spermidine (CaSR/NSCC agonists) at E18-P0 or GABA A receptor agonists at E16-E18. In contrast, [Ca] o -induced slowing of RR at E16-E18 is not reproduced by gadolinium and spermidine. We conclude that perinatal CaSR/NSCC and GABA A inhibition allow quiescence of the LF, thereby improving functional maturation of the RR. V