Effect of serotonin depletion on the central regulation of the carotid sinus reflex in rats.

Effect of serotonin depletion in the rat brain on the sympathetic pressor response to occlusion of the common carotid arteries was examined along with the sequential transection of the brain stem. In rats with the brain serotonin depleted below 10% of control by p-chlorophenylalanine, the reflex pressor response significantly decreased, but the reflex sensitivity was unchanged in any transection regimen, suggesting the decrease originated in the associated hypertension; The infracollicular transection augmented the reflex reaction and sensitivity in both groups, and the medullospinal separation abolished the reflex; It is concluded that the brain serotonin would not be significantly involved in the central regulation of the sympathetic component of the carotid sinus reflex, and that the structure rostral to the midbrain could play an inhibitory role in the integrative regulation.