The response to sulpiride in major depression before and after cognitive behavioural therapy: D2 receptor function.

Background: Previous studies have suggested that antidepressant treatment of depression may potentiate dopamine transmission through increased sensitivity of postsynaptic D2 receptors. Method: 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 was measured by the change in prolactin levels and changes in self-rating scale measures of mood, anxiety and pleasure. Results: The prolactin response to sulpiride (as measured by the maximum prolactin level) was significantly increased after CBT ( z = −2.792, p = 0.005). Sulpiride resulted in an improvement on mood ratings on both test days, but after CBT, this effect was significantly diminished as measured by the Profile of Mood States score ( t = −2.27, p = 0.038). Conclusions: After 16 weeks of CBT, we detected an enhanced prolactin response to sulpiride, suggesting an increased sensitivity of D2 receptor functioning.