Methods: Long-term stability of autonomic and cardiovascular regulation in a decerebrate snake model

A recently developed decerebrate preparation of the rattlesnake, Crotalus durissus, has enabled simultaneous recordings of cardiovascular and respiratory variables, whilst preserving aspects of their control by the autonomic nervous system. However, its reliability for more extended experimental protocols requires further validation of the extent of recovery and temporal stability of autonomic modulation, after decerebration. Here we monitored the recovery of cardiovascular and autonomic variables, checking their temporal stability of autonomic modulation for up to 15 days post-decerebration and assessed their responsiveness to different levels of anesthesia. Cardiovascular variables-including heart rate, stroke volume, cardiac output, systemic and pulmonary arterial pressures, blood flows, conductances, and cardiac shunt-remained stable and comparable to values reported for both intact and previously decerebrated snakes throughout the extended experimental period. Also, both autonomic indexes HRV and baroreflex were operational and consistent across recordings. Additionally, graded increments of anesthesia (isoflurane) produced incremental cardiovascular effects. The maintenance of cardiovascular and autonomic modulation of this wide range of interrelated variables in the decerebrated preparation confirms its adequacy for investigating these systems in long-term experimental protocols.