D serine

Male and female APPKI mice carrying the humanized App gene with Arctic, Swedish, and Beyreuther/Iberian mutations (Saito et al., 2014 (link)) were supplied by the RIKEN Center for Brain Science. The SRRKO mice with a C57BL/6N background were generated as previously reported (Miya et al., 2008 (link)). Wild-type (WT) C57BL/6N mice were also included as a control group in experiments and were used to expand APPKI mice. SRR deleted APPKI (APPKI-SRRKO) mice were generated by crossing APPKI mice with SRRKO mice. Genotyping of APPKI mice was conducted by polymerase chain reaction (Saito et al., 2014 (link)), and genotyping of SRRKO mice was performed using Southern blot analysis as reported (Miya et al., 2008 (link)). All mutant mice were homozygous, and only male mice were used for experiments. Animals were group-housed and maintained in a temperature- and humidity-controlled environment with free access to chow and water. All animal care and experimental procedures were performed according to the Guidelines for the Care and Use of Laboratory Animals at the University of Toyama and approved by the Ethics Committee for Animal Experiments at the University of Toyama (Permission No. A2021 MED-33). For D-serine supplementation, 0.01 M D-serine (TOCRIS, cat no. 0226, Bristol, UK) was added to the drinking water from 9 to 12 months of age.

Pharmacological agents were purchased from:

Sigma Aldrich—BAPTA, bicuculline methobromide, TTX, paraformaldehyde, tannic acid, tergitol, d-serine and all the salts used to prepare the internal and external solutions; Tocris Bioscience—(+)-MK-801 maleate, D-AP5, 8-CPT, and CPA. Bio-Rad—glutaraldehyde.

Pharmacological agents were purchased from: Sigma Aldrich - BAPTA, d-serine, TTX, sodium fluoracetate, CPA, and all the salts used to prepare the internal and external solutions; Tocris Bioscience - (+)-MK-801 maleate, d-AP5, 8-CPT, cPTIO, l-glutamic acid, LY367385, LY341495, MPEP, 2-AG, AM251, L-NAME, DETA NONOate, Nimodipine, Thapsigargin, THL, GDPβS, Calphostin C, Bicuculline, and SCH50911. These compounds were dissolved in water except 8-CPT, 2-AG, AM251, THL, Nimodipine, and Thapsigargin that were dissolved in dimethyl sulphoxide.

Reagents for artificial cerebrospinal fluid (ACSF) and internal solutions, biocytin, 6-nitro-7-sulfamoylbenzo[f]quinoxaline-2,3-dione (NBQX), and picrotoxin were obtained from Sigma-Aldrich. 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), AP-V, dl-TBOA, and d-serine were obtained from Tocris. NBQX, CNQX, and dl-TBOA were dissolved in dimethyl sulfoxide. Tetrodotoxin (TTX) was obtained from Abcam. NTG was obtained from Sigma-Aldrich. picrotoxin was dissolved in ethanol (EtOH). AP-V, d-serine, and TTX were dissolved in ddH₂O.

Picrotoxin and all chemicals used to prepare cutting, recording, and internal solutions were acquired from MilliporeSigma. All NMDAR antagonists (D-APV, MK-801, R-CPP), NMDAR agonist (D-serine), the group 2/3 mGluR agonist (DCG-IV), and MNI-glutamate for uncaging experiments were purchased from Tocris Bioscience. D-APV was also acquired from the NIMH Chemical Synthesis Drug Program. NBQX was purchased from Cayman Chemical Company. The noncompetitive AMPAR selective antagonist LY303070 was custom ordered from ABX Chemical Company. Alexa 594 morphological dye, Alexa 488, and the Ca²⁺ indicator Fluo-5F (Invitrogen) were purchased from ThermoFisher Scientific.