Provided are 2-(piperidin-1-yl)pyrimidin-4(3H)-ones or pharmaceutically acceptable salts thereof, each characterized by having a 1,8-diazaspiro[4.5]deca-3-ene, 1-oxa-8-azaspiro[4.5]deca-3-ene, 2,8-diazaspiro[4.5]deca-3-ene, 2-oxa-8-azaspiro[4.5]deca-3-ene, 2,9-diazaspiro[5.5]undeca-3-ene, 1-oxa-9-azaspiro[5.5]undeca-3-ene, 1,9-diazaspiro[5.5]undeca-4-ene, or 3,9-diazaspiro[5.5]undeca-1-ene structure represented by the following general formula (1):