Localization and quantification of cholecystokinin receptors in rat brain with storage phosphor autoradiography

The present study evaluated a new imaging technique that demonstrated the application of storage phosphor autoradiography in the localization and quantification of cholecystokinin receptors in rat brains and compared the results with film autoradiography. Cryostat sections were incubated with [125I]Bolton-Hunter-labeled sulfated cholecystokinin octapeptide followed by exposure to a storage phosphor-imaging screen and suitable autoradiography film. To obtain satisfactory images, it took 6 days with film autoradiography vs. 15 hours with the storage phosphor technique. Both film and storage phosphor autoradiograms showed the same cholecystokinin receptor distribution in brain sections; however, the film imaged more details. To reach the lowest possible response ratio between low and high receptor density regions in rat brains, storage phosphor autoradiography was about 240-fold faster than film. In addition, the new technique presented a considerably larger exposure time range for maintaining that ratio. The binding per area showed a linear relationship with the thickness of sections between 5 and 14 microns. In the linear response range, the quantitative results of both methods are comparable. In conclusion, storage phosphor autoradiography is a faster technique for localizing and quantifying peptide receptors in tissue sections but slightly compromised in resolution when compared with film autoradiography.