Effects of theta burst stimulation on serotonergic neuronal properties within the dorsal raphe nucleus
Fulton, Timothy F.
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Studies on long-term potentiation (LTP) has been shifting away from induction using high-frequency stimulation in favor of protocols using physiologically relevant levels of stimulation. Previous studies have demonstrated that theta-burst stimulation was effective at inducing LTP using low levels of stimulation, however most of our mechanical understanding of TBS-induced LTP comes from experiments done within the hippocampus. Here, we report that TBS was an effective protocol at inducing LTP in serotonin (5-HT) neurons within the dorsal raphe nucleus (DRN). Additionally, we found that L-type calcium channels (LTCCs) were essential for LTP induction and that this LTP had a presynaptic locus of expression. However, unlike LTP induction within the hippocampus, there was no involvement of N-methyl-D-aspartic acid (NMDA) receptors, yet potentiation still required intracellular calcium flux. These results suggest that DR 5-HT neurons exhibit unique characteristics that allow for a unique mechanism of LTP induction which may have important implications on serotonergic signaling patterns and pharmacological action of SSRIs, dihydropyridines and NMDA receptor antagonists.