Chronic repetitive transcranial magnetic stimulation induces subsensitivity of presynaptic serotonergic autoreceptor activity in rat brain

Repetitive transcranial magnetic stimulation (rTMS) is a novel procedure which has proven effective in the treatment of major depression. We administered rTMS chronically to rats in order to determine whether this procedure affected serotonergic neurotransmission in the prefrontal cortex. Basal 5-HT levels, and the effects of challenges with the 5-HTIA receptor agonist 8-OH-DPAT and the 5-HTIB antagonist GR 127935 on 5-HT levels were determined using in vivo microdialysis. Rats which had undergone chronic rTMS showed reduced responses to both challenges, indicating subsensitivity of both the presynaptic 5-HTIA autoreceptors situated somatodendritically in the raphe nuclei and the 5-HTIB autoreceptors situated on nerve terminals. Since such subsensitivity has been demonstrated after other antidepressant treatments, our results indicate that these treatments and rTMS may have a common mechanism of action. NeuroReport 11:2925-2929 (C) 2000 Lippincott Williams & Wilkins.