Regional distribution of 5-hydroxytryptamine in cat brain

The regional distribution of serotonin (5-HT) in the brain of the cat is poorly understood. In this work, serotonin was analyzed fluorometrically along the brain stem and prosencephalon of the cat. The hypothalamus had the highest concentration of serotonin. Serotonin decreased gradually at the mesencephalon, preoptic area, medulla oblongata, hippocampus, pons, visual cortex, spinal cord and frontal cortex. Significant differences were found between the raphe (3 mm thick) and the lateral blocks of the brain stem. The concentration of serotonin is higher in the raphe blocks, though it decreases caudally. There is no significant difference between the raphe (4 mm thick) and the lateral block of the brain stem. The results demonstrate the regional concentration of serotonin in the CNS of a normal cat, the relationships between serotoninergic neuron groups and serotonin concentration,and the probable significance of nerve terminals and varicosities in storing serotonin.