PARAPYRAMIDAL ROSTROVENTROMEDIAL MEDULLA AS A RESPIRATORY RHYTHM MODULATOR

After inhalation of 15% CO2, immunoreactions to glutamate and glutamic acid decarboxylase were found in some c-Fos or c-Jun-labeled neurons distributed in the reticular region just dorsal to the pyramidal tract in the rostroventromedial medulla (parapyramidal RVMM). This region f orms vertically the narrow strip between the nucleus raphe pallidus an d nucleus parapyramidalis superficialis, and extends rostrocaudally fr om the level just ahead of the inferior olivary complex to the level j ust behind the nucleus of the trapezoid body. When we placed lesions w ith kainate in the parapyramidal RVMM, hyperpneic and tachypneic respo nses to brief inhalation of 15% CO2 were completely abolished, and the eupneic rhythm changed into the gasping rhythm. This study suggests t hat the parapyramidal RVMM consists of neuronal substrates that subser ve as the respiratory rhythm modulator.