6 7 dinitroquinoxaline 2 3 1h 4h dione dnqx

DL-2-amino-5-phosphonopentanoic acid (DL-APV; an NMDA antagonist; Sigma-Aldrich) and tetrodotoxin (a voltage-dependent Na⁺ channel blocker; Sigma-Aldrich) were dissolved in water. (-)-QNP (a dopamine D₂ agonist; Tocris Bioscience) was dissolved in water (for ex vivo recordings) or saline (for intraperitoneal injection). 6,7-Dinitroquinoxaline-2,3(1H,4H)-dione (DNQX; an AMPA antagonist; Tocris Bioscience), bicuculline (a GABA_A antagonist; Enzo Life Science), raclopride (a D₂ antagonist; Abcam Biochemicals), PD98059 [a mitogen-activated protein kinase kinase (MEK) inhibitor; Cayman Chemical Company], and CGS 21680A (an A_2A receptor agonist; Toronto Research Chemicals) were dissolved in dimethyl sulfoxide (DMSO). Stock solutions were stored at –20°C until use and dissolved in saline, artificial CSF (ACSF), or pipette solution. The final concentration of DMSO was lower than 5% for intraperitoneal injection and microinjection and 0.05% for electrophysiology.

(-)Nicotine tartrate (MP Biomedicals) was dissolved in sterile 0.9% saline, and pH was adjusted to 7.2–7.4 using 1 m NaOH. E2 was purchased from Sigma-Aldrich and diluted to 3 μg/0.1 ml in sesame oil (Sigma-Aldrich). E1 was purchased from Sigma and was diluted to 10 μg/0.1 ml in 3 μg/0.1 ml E2 in sesame oil (Sigma-Aldrich). 6,7-dinitroquinoxaline-2,3(1H,4H)-dione (DNQX) was purchased from Tocris Biotechne and diluted to a stock concentration of 20 mm in dimethyl sulfoxide (DMSO). Before recordings, DNQX was diluted to a working concentration of 20 μm in recording aCSF.