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Differential effect of 5-hydroxytryptophan on approach and avoidance behavior in rats
W K Park1, J N Hingtgen, M H Aprison
1Department of Psychiatry, Indiana University School of Medicine, Indianapolis 46202-4887.
Pharmacology, Biochemistry, and Behavior
|January 1, 1991
Summary
Serotonin, specifically 5-hydroxytryptophan (5-HTP), selectively suppresses food-reinforced approach behavior in rats. Avoidance behavior remains unaffected, suggesting distinct neurotransmitter roles.
Area of Science:
- Neuroscience
- Behavioral Pharmacology
- Animal Models of Behavior
Background:
- The hypersensitive postsynaptic serotonin receptor theory of depression links serotonin to mood regulation.
- Previous animal models showed 5-hydroxytryptophan (5-HTP) suppressed food-reinforced approach behavior.
Purpose of the Study:
- To investigate the selective effects of 5-hydroxytryptophan (5-HTP) on approach versus avoidance behaviors in rats.
- To clarify the role of serotonin in mediating different types of learned behaviors.
Main Methods:
- Adult male Wistar rats were trained on Sidman avoidance and food-reinforced approach schedules.
- Rats received 5-hydroxytryptophan (5-HTP) administration (L-5-HTP or D,L-5-HTP) during separate and combined behavioral sessions.
- Behavioral suppression of approach and avoidance responses was measured.
Main Results:
- 5-Hydroxytryptophan (5-HTP) administration significantly suppressed food-reinforced approach behavior in a dose-dependent manner.
- No significant effect of 5-HTP was observed on Sidman avoidance responding.
- Selective suppression of approach behavior occurred even when both schedules were combined.
Conclusions:
- These findings support a specific role for serotonin in modulating food-reinforced approach behavior.
- The results suggest that avoidance behavior suppression may involve other neurotransmitter systems distinct from serotonin.