Response of medullary neurons to step changes in carotid sinus pressure

Moderate amplitude step changes in carotid sinus pressure were found, in an open-loop baroreflex preparation, to produce equivalent step changes in the firing rate of a majority of the medullary neurons tested. The average firing rate remained constant so long as the pressure was held constant (up to 24 sec). No rate sensitivity was observed in 32 out of 33 neurons; however, a single neuron showed mean firing rate changes only during pressure transitions. The variety in the activity patterns of cells which, on the average exhibited stereotyped responses to a simple repetitive stimulus, suggests that afferent information may undergo considerable integration and restructuring within the sensory nucleus, rather than being 'relayed' intact to other regions.