Post mortem receptor mapping of the human brain Håkan Hall Department of Clinical Neuroscience, Karolinska Institute, Stockholm

Visualization of receptors and transporters in the human brain can be achieved with a large number of techniques. In vivo techniques include PET and SPECT, as well as ex vivo assays, where the analyses are performed in vitro after in vivo administration of the compound. In vitro visualization of human brain receptors and transporters can be performed using a number of techniques, such as autoradiography, in situ hybridization and immunohistochemistry. In vitro autoradiography is commonly used for the study of distribution and regional pharmacology of receptors, in both micro- and macroscopical levels. The present communication deals with autoradiography using post mortem human whole hemispheres (whole hemisphere autoradiography, WHA), and the use of this technique as a tool for the study of receptor distribution in the control and diseased brain. This technique is especially useful when performing comparisons with in vivo techniques like PET and SPECT. Radioligand autoradiography with the same radioligands (however normally with long-lived isotopes in vitro) can result in high resolution images that are complementary to the PET / SPECT images.

The techniques used for WHA will be described in detail. Special emphasis will be put on the use of different isotopes (³H, ¹¹C, ¹⁸F and ¹²⁵I) and correlation with in vivo binding using PET and SPECT.  Examples from the work performed at the Karolinska Institutet, Stockholm, Sweden on receptor and transporter distribution of mainly dopamine (D₁, D₂ and D₃ dopamine receptors, dopamine transporter) and serotonin receptor subtypes (5–HT_1A, 5–HT_1B/D, 5–HT_2A, 5–HT₄, 5–HT₆, 5–HT₇ and serotonin tranpsorter) will be shown.