Suppression of diaphragmatic activity during spontaneous ponto-geniculo-occipital waves in cat

It has been reported that spontaneous ponto-geniculo-occipital (PGO) waves, which occur during REM sleep in the cat, are associated with a brief inhibition of diaphragmatic activity (Orem, 1980). This report was preliminary and not supported by a detailed analysis. We report here analysis of the relationship between PGO waves and diaphragmatic activity based on 3073 PGO waves recorded simultaneously with diaphragmatic activity. The results show that there is indeed an inhibition of diaphragmatic activity during PGO waves. This inhibition has an amplitude up to 20% of background, and a duration (approximately 80 ms) approximately coinciding with the temporal duration of the PGO wave. In addition, we analyzed the relationships among the activity of medullary respiratory neurons, PGO waves, and diaphragmatic activity. Two neurons were observed whose relationships to diaphragmatic activity and PGO waves were consistent with the idea that they mediated the PGO-associated inhibition of diaphragmatic activity. However, the number of PGO waves involved in the analysis of the interaction between medullary respiratory neuronal activity and diaphragmatic activity was small and, although suggestive, was not conclusive.