In conventional pharmacological research in the field of mental disorders, pharmacological effect and dose have been estimated by ethological approach and in vitro data of affinity to the site of action. In addition, the frequency of administration has been estimated from drug kinetics in blood. However, there is a problem regarding an objective index of drug effects in the living body. Furthermore, the possibility that the concentration of drug in blood does not necessarily reflect the drug kinetics in target organs has been pointed out. Positron emission tomography (PET) techniques have made progress for more than 20 years, and made it possible to measure the distribution and kinetics of small molecule components in living brain. In this article, we focused on rational drug dosing using receptor occupancy and proof-of-concept of drugs in the drug development process using PET.
Brain ; Central Nervous System ; Drug Evaluation ; Electrons ; Kinetics ; Mental Disorders ; Norepinephrine Plasma Membrane Transport Proteins ; Positron-Emission Tomography ; Receptors, Dopamine D2 ; Serotonin Plasma Membrane Transport Proteins

Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is useful for diagnosing mediastinal lymph node lesions. Cell blocks prepared from the needle washing fluid and flow cytometry of tissue samples are helpful in making the diagnosis, but the combination of both examinations is not routinely performed. A 77-year-old woman with fever, dyspnea, and anorexia was admitted to our hospital. Computed tomography showed enlarged mediastinal lymph nodes with calcification and left ureteral calculus; however, no focus of infection was identified. We suspected lymph node tuberculosis or malignant lymphoma, and EBUS-TBNA was performed to evaluate the mediastinal lymph node lesions. Because a cell block prepared from the needle rinse fluid was suspicious for malignant lymphoma, we changed the puncture needle from 22 G to 19 G and performed a second EBUS-TBNA. Diffuse large B-cell lymphoma (DLBCL) was diagnosed based on the results of flow cytometry of the EBUS-TBNA samples. Here we report this case of DLBCL in which mediastinal lymph node tuberculosis was suspected and cell block preparation and flow cytometry using EBUS-TBNA specimens were useful for the diagnosis.