Serotonin agonists (increasing serotonin at specific receptor sites, 5-HT2A specifically in this case), such as psychedelics, are shown to attenuate stress-induced learned helplessness (dynorphin at kappa opioid receptors).
Dynorphin expression is moreso implicated in learned helplessness or aversive learning.
This requires the activation of the serotonin transporter (SERT), which actually decreases serotonin activity.