CLASSIFICATION OF COUPLING PATTERNS AMONG SPONTANEOUS RHYTHMS AND VENTILATION IN THE SYMPATHETIC DISCHARGE OF DECEREBRATE CATS

The spontaneous low- and high-frequency rhythms in the sympathetic dis charge of decerebrate artificially ventilated cats are affected by ext ernal ventilation, Two graphical methods (i.e. the space-time separati on plot and the frequency tracking locus) are used to classify the non -linear interactions. The observed behaviours in the sympathetic disch arge consist of phase-locked periodic dynamics (at various frequency r atios with ventilation), quasiperiodic and aperiodic patterns. They de pend on the experimental condition. In control condition the sympathet ic discharge appears more frequently locked to each ventilatory cycle (1:1 dynamics). However, some cases of quasiperiodic dynamics are foun d. A sympathetic activation stimulus, such as inferior vena cava occlu sion, is able to synchronise slow rhythms in the sympathetic discharge to a subharmonic of ventilation. During a sympathetic inhibition stim ulus, such as aortic constriction, 1:1 dynamics is detected but the am plitude of the sympathetic responses can be modulated by unlocked slow rhythms. Moreover, some cases of aperiodic dynamics are observed. Vag otomy reduces the 1:1 coupling between sympathetic outflow and ventila tion. Vagotomy plus spinalisation disrupts periodic dynamics in the sy mpathetic discharge so that irregular and complex patterns are found.