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:

Role of oestrogen receptors on the modulation of NADPH-diaphorase-positive cell number in supraoptic and paraventricular nuclei of ovariectomised female rats. Modulation of the nitric oxide producing system (demonstrated via the NADPH-diaphorase histochemical reaction) by oestradiol has been established in several structures of the rat brain. The present study aimed to explore the possible regulation of NADPH-diaphorase activity by oestradiol in neurones of the supraoptic (SON) and paraventricular (PVN) nuclei and the role of oestrogen receptors (ERα and ERβ) in this regulation. Adult ovariectomised rats were divided into six groups and injected either with vehicle or a single dose of oestradiol, a selective ERα agonist-PPT [4,4',4″-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol], a selective ERβ agonist-DPN [2,3-bis(4-hydroxyphenyl)-propionitrile], a selective ERα antagonist-MPP [1,3-bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy)phenol]-1H-pyrazole dihydrochloride] or a selective ERβ antagonist-PHTPP (4-[2-phenyl-5,7-bis(trifluoromethyl)pyrazolo[1,5-a]pyrimidin-3-yl]phenol). The number of NADPH-diaphorase positive elements in the SON and the PVN was modulated by both ERs but, depending on the nucleus, ERα and ERβ ligands induced different effects. These results suggest that the regulation of nitrergic system by ERs may play a role in the control of oestrogen-dependent physiological mechanisms regulated by the SON and the PVN.
{"Chemical": ["NADPH", "oestradiol", "PPT", "2,3-bis(4-hydroxyphenyl)-propionitrile", "4-[2-phenyl-5,7-bis(trifluoromethyl)pyrazolo[1,5-a]pyrimidin-3-yl]phenol", "oestrogen", "DPN", "1,3-bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy)phenol", "MPP", "PHTPP", "1H-pyrazole dihydrochloride", "nitric oxide", "4,4\u0027,4\u2033-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol"]}