The Pet Centre

The PET Centre is dedicated to brain research using Positron Emission Tomography (PET), a three-dimensional scan that maps how the mind works by measuring, in detail, the functioning of distinct areas of the brain. Its main focus is on studying chemical brain messengers through PET methods, to better understand the neurochemical root of mental illness and addiction. The ultimate goals are to improve the lives of clients and their families by enhancing the effectiveness of existing treatments and reducing the side effects of medication. To achieve these goals, CAMH scientists use PET methods to find diagnostic markers for disease, and to encourage innovative approaches to drug development by using PET in the early stages of evaluating new drugs.

Currently, research in the PET Centre is focused on developing new PET techniques and imaging agents to understand the molecular basis of neurological and psychiatric disorders. The PET Centre has research programs in radiochemistry, PET methodology, schizophrenia, depression, addictions, and aging. The PET Centre has active collaborations with clinicians and scientists in other institutions affiliated with the University of Toronto as well as international research partnerships.

More information is also available at www.camhpet.ca.

Summary of Activities

In addition to the production of established radiotracers for human and animal PET studies, the research team is looking for novel radiotracers and better synthetic methods of creating new radioactive chemical compounds.

CAMH developed the first dopamine D₂ agonist radiotracer used in humans, which is now used by most of the leading PET centres around the world. CAMH scientists also invented a new method for the radiosynthesis of PET tracers that has been patented and licensed to a commercial company.

Visit Radiochemistry Breakthrough for more information.

Selective tracers are used at their target sites to measure the occupancy of selective serotonin reuptake inhibitor (SSRIs). The results have had an immediate impact on clinical dosing. Measuring the serotonin transporter occupancy using PET and radiotracers of the class developed at CAMH is now the standard method used by industry when assessing new antidepressants.

Using PET methods, CAMH scientists revolutionized medication doses for depression and schizophrenia. They discovered the percentage of brain occupancy (percentage of receptors blocked by medication), to achieve effectiveness without debilitating side effects, in both depression (about 80 percent occupancy) and schizophrenia (about 60 percent occupancy).

Visit Antipsychotic drugs improve psychosis in patients within 24 hours of treatment for more information related to schizophrenia.

Scientists in the PET Centre detailed a new monoamine model of depression. For over 30 years, scientists believed that monoamines -- mood-related chemicals such as serotonin, norepinephrine, and dopamine -- are low in the brain during major depressive episodes. However, no one had ever found a convincing explanation for monoamine loss until CAMH investigated whether brain monoamine oxidase A (MAO-A) -- an enzyme that breaks down chemicals like serotonin, norepinephrine, and dopamine -- was higher in those with untreated depression. The results showed that in major depression MAO-A was significantly higher in every brain region that the scientists investigated. On average, MAO-A was 34 percent higher. A second part of this new model is that monoamine transporters have an important role in removing monoamines away from active sites.

Visit New Depression Model Advances Disease Frontiers for more information.