Neurocatin induces changes in release and level of serotonin in synaptosomal fraction from rat brain

A newly isolated factor from mammalian brain, neurocatin, is shown to increase both the level and release of serotonin in suspensions of synaptosomes isolated from rat brain. Incubation of synaptosomes for 10 min with approximately 20 nM neurocatin resulted in release of about 50% of the total pool of serotonin. Quantification of serotonin and its major metabolite, using an electrochemical detector, indicated that the presence of neurocatin also caused an increase in the absolute level of serotonin and decrease in its catabolism to 5-hydroxyindoleacetic acid (5-HIAA). The effect is dependent on the time of incubation and concentration of neurocatin. At a concentration of 20 nM, neurocatin increased about 60% the level of serotonin and decreased about 50% the level of 5-HIAA. Depolarization conditions--50 microM veratridine and 50 mM K+ medium--increased release of serotonin by 50% and 30% respectively without affecting the level of serotonin or its catabolism to 5-HIAA.