the ability to act reversibly and as an ion channel, provide other areas of research. schizophrenia main article: schizophrenia chemical structure of 3-methoxy-4-hydroxyphenylglycol (mhpg), a metabolite of ne. abnormally high levels of mhpg are also indicative of impaired ne regulation. the role of ne in schizophrenia has not been fully understood, but has stimulated research into this topic. the only relationship that has been understood between researchers is that there is a positive correlation between increased ne levels in the brain and spinal fluid (csf) and activity of schizophrenia. in one study, clonidine, a drug used to treat medical conditions such as adhd and high blood pressure, was shown to produce a significant decrease in plasma level mhpg (3-methoxy-4-hydroxyphenylglycol), a metabolite of ne, in the normal control group, but not in the group of schizophrenic patients. this suggests that in schizophrenia, the alpha-2 adrenergic receptor, a presynaptic inhibitory receptor, may be less sensitive compared to normally functioning alpha-2 receptors and thus relate to elevated ne levels in the disorder. in addition to increased ne levels in the brain and csf, increased levels of mhpg has also been associated with a diagnosis of schizophrenia. impaired ne regulation in schizophrenia has been an area of interest for researchers and research on this topic is still ongoing. imaging via positron emission tomography imaging technique, net has been selectively investigated. 11c me@hapthi and 18f-mener are two net selective radio tracers for pet imaging. fluorescent substrates for the transporter can also be used to monitor the transporter rate in isolated organs or tissues, although these are not suitable for clinical imaging.