Background:
Previous studies of D2 receptor function in depressed patients have shown mixed results, with some (but not all) reporting increased sensitivity/ upregulation of D2 receptors in untreated depression, while others report that effective treatment results in increased sensitivity/upregulation.
Methods:
D2 receptor function was assessed in 24 patients with major depression before and 16 patients after 16 weeks of treatment with cognitive behavioural therapy (CBT) using a challenge with a selective D2 antagonist, sulpiride. Four hundred milligrams of sulpiride was administered orally on two test days and response measured in two different dopaminergic pathways: the change in prolactin secretion (tuberoin-fundibular pathway) and changes in self-rating scale measures of mood (VAS, POMS), anxiety (STAI) and pleasure (SHPS) (mesocorticolimbic pathway).
Results:
There was no significant difference in the prolactin response to sulpiride before and after treatment (z = −1.4, P = 0.156). On both test days, sulpiride led to an improvement in mood (VAS and POMS scales). After CBT, this effect was significantly reduced as measured by the POMS scale (t = −2.3, P = 0.038) but unchanged on the VAS scale. Although patients exhibited significant clinical improvement after treatment (as measured by percentage improvement in HDRS score), there was no correlation between response to CBT and changes in response to sulpiride in either pathway.
Conclusions:
No change in tuberoinfundibular D2 receptor function was detected following CBT. A change in mesocorticolimbic D2 receptor function was detected; however, no relationship between changes in D2 receptor sensitivity and clinical response to CBT was evident in this group of depressed patients.
