We are trying to directly monitor the levels of serotonin in our control vs experimental mice to ensure that our drug is working (SSRI) regularly throughout our treatment course. We are trying to avoid using a more invasive blood collection technique (e.g. suborbital eye bleeds) or sacrificing mice at each time point, if possible. We regularly process blood to isolate platelets in our lab, but do not have experience with a volume this small. Also, do not want to use urine analysis of the breakdown product 5-HIAA, as it is too indirect. Let me know if anyone has experience or any ideas of removing the RBCs or a protocol that would assist me.