You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Effects of antipsychotics on the BDNF in schizophrenia. Brain-derived neurotropic factor (BDNF) is involved in the development of the brain, and likely influences the neuroplasticity in schizophrenia. BDNF is also believed to interact with other neurotransmitter systems implicated in schizophrenia, such as dopamine, glutamate, serotonin and GABA. Therefore, BDNF is a candidate gene for schizophrenia. In past decades, the blood (serum or plasma) BDNF protein levels and BDNF gene alleles and genotypes to the clinical features of schizophrenia, such as age of onset, clinical subtypes, symptom severity, and drug response, have been evaluated among different populations. However, the results are still inconsistent. Further, different drugs have been reported to have different effects on BDNF protein levels. A cross-sectional survey revealed that serum BDNF levels in chronic schizophrenic patients treated with clozapine exceeded those of patients treated with risperidone or with typical antipsychotics. In recent times, BDNF epigenetic studies have also been conducted in clinical studies of schizophrenia to address the question of why patients with the same gene genotype and alleles have different clinical presentations. In addition, the effects of different antipsychotic drugs on gene methylation and protein acetylation have also been reported. In conclusion, more data are needed regarding BDNF in the brain and in peripheral blood, including protein levels, single nucleotide polymorphisms, epigenetic regulation, and clinical data in order to understand the role of BDNF in schizophrenia.
{"Chemical": ["risperidone", "serotonin", "glutamate", "dopamine", "GABA", "clozapine"]}