The disposition of intravenously injected C
14-amitriptyline in the brain was studied in cats. The regional distribution of the radioactivity was uneven. The concentration in the cerebral and cerebellar cortex and hippocampus, and some subcortical nuclei showed the highest accumulation a short time after the injection. Four hours after the injection the radioactivity in the grey matter decreased, when the white matter showed the highest activity. The distribution of amitriptyline was compared with C
14-glucose and I
131-albumin. The distribution of amitriptyline is more similar to the distribution of radioactivity after administration of C
14-glucose than that after injection of I
131-albumin. The implications of these distribution studies for the mode of action are discussed.
The authors are grateful to Fa. Hoffmann-La Roche & Co., Basel, Switzerland, who generously provided C14-amitriptyline (C14-Laroxyl). Thanks are due to Mr. H. Sundberg, Mrs. M. Merseburg and Mrs. G. Mabo for their valuable technical assistance. The authors are also indebted to Knut and Alice Wallenbergs Stiftelse for general equipment for isotope research work.