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

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Abstract
The binding affinity (Bmax, Kd) of [3H]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 Bmax 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 Kd was 0.5 .+-. 0.3 nM comparable to the Kd of the controls (0.6 .+-. 0.2). After 6 weeks of treatment the clomipramine group (n = 11) had significantly lower Bmax = 208.5 .+-. 286 (P < 0.001). In the maprotiline-treated patients (n = 18) the Bmax values (1221 .+-. 258 ) tended to increase towards the values of the controls but without statistical significance. No significant statistical correlation was found between initial Bmax values and clinical outcome.