Effects of electroconvulsive therapy on cerebral A(1) adenosine receptor availability: a PET study in patients suffering from treatment-resistant major depressive disorder

INTRODUCTION: Sleep deprivation and electroconvulsive therapy (ECT) effectively ameliorate symptoms in major depressive disorder (MDD). In rodents, both are associated with an enhancement of cerebral adenosine levels, which in turn likely influence adenosinergic receptor expression. The aim of the current study was to investigate cerebral A(1) adenosine receptor (A(1)AR) availability in patients with MDD as a potential mediating factor of antidepressant effects of ECT using [(18)F]CPFPX and positron emission tomography (PET). METHODS: Regional A(1)AR availability was determined before and after a series of ECT applications (mean number ± SD 10.4 ± 1.2) in 14 subjects (4 males, mean age 49.5 ± 11.8 years). Clinical outcome, measured by neuropsychological testing, and ECT parameters were correlated with changes in A(1)AR availability. RESULTS: ECT had a strong antidepressive effect (p < 0.01) while on average cerebral A(1)AR availability remained unaltered between pre-and post-ECT conditions (F = 0.65, p = 0.42, mean difference ± SD 3.93% ± 22.7%). There was no correlation between changes in clinical outcome parameters and regional A(1)AR availability, although individual patients showed striking bidirectional alterations of up to 30–40% in A(1)AR availability after ECT. Solely, for the mean seizure quality index of the applied ECTs a significant association with changes in A(1)AR availability was found (r(s) = −0.6, p = 0.02). DISCUSSION: In the present study, therapeutically effective ECT treatment did not result in coherent changes of A(1)AR availability after a series of ECT treatments. These findings do not exclude a potential role for cerebral A(1)ARs in ECT, but shift attention to rather short-termed and adaptive mechanisms during ECT-related convulsive effects.