pH Sensitivity of Spinal Cord Rhythm in Fetal Mice in Vitro
The spinal respiratory rhythm generator is a neural network localized at the segments C4-C6 able to produce synchronous long lasting rhythmic bursts of action potentials on both phrenic nerves (Dubayle and Viala, 1996). As other spinal cord rhythms, the spinal respiratory rhythm can be induced in curarized rabbits after cervical transection by administration of nialamide-DOPA (Viala and Freton, 1983). This spinal rhythm can also be induced in the in vitro brainstem-spinal cord preparation from newborn rat or mouse by deep diethyl ether anaesthesia, or bath administration of glutamic acid, N-methyl-D-aspartic acid, amphetamine, 5-hydroxytryptophan, or high potassium concentration (Dubayle and Viala, 1998). It has been shown that the spinal respiratory rhythm recorded from neonatal rat brainstem-spinal cord preparation is sensitive to H+ and CO2 (Dubayle and Viala, 1998). However, in most of the experiments the extent to what this chemosensitive response depends directly on the spinal respiratory generator was undefined, because chemical stimulation or the pharmacological inductors affect also the activity of the medullary respiratory pattern generator and both, the medullary and spinal respiratory oscillators, are coupled (Dubayle and Viala, 1996). Uncoupling of these generators by spinal transection at C2 segment caused the disappearance of the spinal respiratory rhythm in most of the neonatal preparations (Dubayle and Viala, 1998).
KeywordsRespiration Bicarbonate Diethyl Ketamine Amphetamine
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