Brain [H-3]cAMP binding sites are unaltered in depressed suicides, but decreased by antidepressants

Saturation binding of [H-3]cAMP to the regulatory subunit of cAMP-dependent protein kinase (PKA) was measured in the soluble fraction of brain samples, obtained at post-mortem, from suicides with a firm retrospective diagnosis of depression and individually matched controls. Suicides were subdivided into those who had been free of antidepressant drugs for at least 3 months and those in whom prescription of antidepressants was clearly documented. In antidepressant-free suicides, we found no significant differences in the number or affinity of [H-3]cAMP binding sites in the five regions studied. In antidepressant-treated suicides however, B-max values were lower in all regions, reaching statistical significance in parietal cortex and amygdala. K-d values for antidepressant-treated suicides were significantly higher in parietal cortex, temporal cortex and amygdala. These results suggest the regulatory subunit of PKA is unaltered in depression, but is influenced by antidepressant drugs.