Film images were scanned (ScanMaker 9800XL, Microtek, Cerritos, CA, USA) and densitometry performed using NIH Image software (U.S. National Institutes of Health, http://rsb.info.nih.gov/nih-image/). Mean binding densities in select brain regions (see Table 1) were calculated and converted to nCi/mg tissue weight based on a best-fit 3rd degree polynomial formula that incorporates tissue equivalent values provided by Amersham. Brain areas were outlined using a rat brain atlas (Paxinos and Watson, 1998). Densitometric measurements were obtained from 3–4 near adjacent sections to measure total and nonspecific binding for each structure within each rat. Nonspecific binding (determined in sections adjacent to total binding sections) was subtracted from total binding to obtain specific binding values used in data analysis. Densitometry was performed on original images that were in no way digitally manipulated. Example photomicrographs were uniformly transformed across groups to a color scale using NIH Image J.
