Cardiac‐related and other rhythmic activity of neurons in the rostral ventrolateral medulla (RVLM) of conscious cats: effects of vestibular lesions

Recordings were made from neurons in the RVLM in conscious cats before and after removal of vestibular input through a bilateral vestibular neurectomy. Blood flow through the carotid artery was also measured so we could determine whether a unit had cardiac‐related activity (CRA). Only a small fraction of RVLM neurons exhibited CRA, but the fraction increased from 4% to 9% following vestibular lesions. CRA neurons were often clustered: multiunit recordings revealed that when a CRA unit was present, another was in the same field approximately 50% of the time. In 32% of the instances where pairs of RVLM neurons with CRA were examined at the same location, short time scale interactions between their discharges were demonstrated. Frequency‐domain analysis revealed that a small fraction of RVLM neurons with CRA displayed higher‐frequency components (10–30 Hz) as well, most often after vestibular lesion. These data suggest that rhythmic firing of RVLM neurons including CRA may be ‘state dependent,’ and is masked until the animal is alerted or agitated.