Evidence for a serotonergic mechanism of the learned helplessness phenomenon.
The present experiments examined the role of the serotonergic system in the learned helplessness phenomenon. In Experiment 1, a 200 mg/kg dose of 1-tryptophan injected 30 min prior to testing disrupted acquisition of Fixed Ratio 2 shuttle escape behavior. In Experiment 2, a 100 mg/kg dose of 5-HTP produced interference with the acquisition of the escape response. Furthermore, this interference was prevented by treatment with the serotonergic antagonist methysergide. In Experiment 3, animals were pretreated with a subeffective dose of 1-tryptophan in combination with subeffective exposure to inescapable shock. These animals showed a deficit in the acquisition of FR-2 shuttle escape. In Experiment 4, combined exposure to a subeffective dose of 5-HTP and inescapable shock (40 trials) resulted in an acquisition deficit. This deficit was reversed by methysergide. Experiment 5 showed that the detrimental effects of exposure to prolonged (80 trials) of inescapable shock can be prevented by treatment with methysergide. These studies implicate the serotonergic system as a possible mediator of the learned helplessness phenomenon.
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004597:Electroshock; D004924:Escape Reaction / Q000187:drug effects / Q000502:physiology; D006380:Helplessness, Learned / Q000523:psychology*; D006801:Humans; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D009115:Muridae; D011930:Reaction Time / Q000502:physiology; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000502:physiology*; D014364:Tryptophan / Q000494:pharmacology
D011985:Receptors, Serotonin; D012701:Serotonin; D014364:Tryptophan; D008784:Methysergide