[3H]Imipramine binding in idiopathic pain syndromes. Basal values and changes after treatment with antidepressants☆

Abstract The binding affinity (B max , K d ) of [ 3 H]imipramine to platelet membranes was investigated in 43 patients with a diagnosis of idiopathic pain syndrome. Measurements were carried out prior to and after 6 weeks' treatment with the antidepressants clomipramine or maprotiline (randomized double-blind trial). Before treatment the B max was 11% lower (1109 ± 237 fmol/mg protein) compared to historical control subjects (n = 21, 1240 ± 390) and comparable to patients with psychogenic pain with affective symptoms ( n = 62, 1110 ± 360) previously measured at the same laboratory. The K d was 0.5 ± 0.3 nM comparable to the K d of the controls (0.6± 0.2). After 6 weeks of treatment the clomipramine group ( n = 11) had significantly lower B max = 208.5 ± 286 ( P n = 18) the B max values (1221± 258) tended to increase towards the values of the controls but without statistical significance. No significant statistical correlation was found between initial B max values and clinical outcome.