Quantification of Neurotransmitter Receptors

We used 5-month-old naïve OM and S5B rats. Slides with mounted brain sections at the level of dorsal striatum that were stored at −80°C were gradually brought back to room temperature and then exposed to receptor autoradiography procedures using [³H]spiperone, [³H]SCH23390, [³H]MPEP, and [³H]SR141716A as previously described^{21 (link), 26 (link)–28 (link)}. Radioactivity concentrations were verified via liquid scintillation counting. For [³H]spiperone and [³H]SCH23390 experiments, slides were placed in BAS-TR 2025 (GE Healthcare, Piscataway, NJ) phosphor imaging plates for 7 days along with [¹⁴C] standards (GE Healthcare, Piscataway, NJ) (calibrated against ³H-impregnated brain paste standards). Imaging plates were developed using an FLA-7000 phosphorimager (GE Healthcare, Piscataway NJ). Using Multigauge® software (GE Healthcare, Piscataway, NJ), regions of interest (ROIs) were drawn on the dorsolateral (DLST) and dorsomedial striatum (DMST) of each section. Values were averaged and initially expressed as PSL/mm² and subsequently converted to dpm/mg with the use of [¹⁴C] standards. For [³H]MPEP and [³H]SR141716A experiments, slides were imaged using a β-imager (Biospace Lab, France). Scanning and image analysis methods were performed as previously described^{21 (link)}.