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:

An evaluation of the serotonin system and perseverative, compulsive, stereotypical, and hyperactive behaviors in dopamine transporter (DAT) knockout mice. RATIONALE: Mice lacking the dopamine transporter (DAT) display major behavioral alterations that include hyperactivity, perseverative locomotor patterns, and reduced prepulse inhibition of the acoustic startle reflex. OBJECTIVES: The objectives of this study were to investigate perseverative, compulsive, stereotypical, and hyperactive behaviors, as well as serotonin and its involvement with these behaviors, in DAT gene-altered mice. RESULTS: In the open field, mean turn angle and meandering were decreased in DAT knockout (DAT-KO) mice. DAT-KO mice displayed increased hyperactivity, increased velocity, less time immobile, and a failure to habituate over time in the open field unlike their DAT wildtype (DAT-WT) and heterozygous (DAT-HET) littermates. DAT-KO mice buried fewer marbles than DAT-WT and -HET mice in an assessment of compulsive-like behaviors, likely due to extreme hyperactivity and related inattention. Stereotypical head weaving was increased in untreated DAT-KO mice. Following administration of the 5-HT(1A/7) agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), stereotypical head weaving and forepaw treading were increased more in DAT-KO mice than in DAT-WT or -HET mice. By contrast, head twitches induced by treatment with the 5-HT(2A/2C) agonist (±)-2,5-dimethoxy-4-iodophenyl-2-aminopropane (DOI) were similar in mice of all three DAT genotypes. 5-HT(1A) autoreceptor function was intact in DAT-KO mice. Compared to DAT-WT mice, serotonin levels were increased in DAT-HET and -KO mice in frontal cortex and hippocampus, respectively, and serotonin turnover rates were increased ∼30 % in the striatum of DAT-KO mice. CONCLUSIONS: These findings extend and confirm prior behavioral and biochemical characterization of DAT-KO mice. Hyperactivity, stereotypy, and perseverative behaviors are increased in these mice, with brain-area specific increases in serotonin levels and serotonin turnover, and marked increases in postsynaptic 5-HT(1A) receptor-mediated stereotypic responses.
{"Chemical": ["5-HT", "serotonin", "(\u00b1)-2,5-dimethoxy-4-iodophenyl-2-aminopropane", "DOI", "dopamine", "8-hydroxy-2-(di-n-propylamino)tetralin", "8-OH-DPAT"]}