Trial reportPsychopharmacology2011
Effects of tryptophan depletion and tryptophan loading on the affective response to high-dose CO2 challenge in healthy volunteers.
Trial report in Psychopharmacology, 2011. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 4 papers, 2 of them syntheses that pooled it.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
4 citing papers in PubMed, 2 syntheses or guidelines pooled it, 11 citations in OpenAlex.
- Pharmacological effects on 35% COJournal of psychopharmacology (Oxford, England) · 2025Pooled it
- Effects of tryptophan depletion on anxiety, a systematic review.Translational psychiatry · 2021Pooled it
- Acid-base dysregulation and chemosensory mechanisms in panic disorder: a translational update.Translational psychiatry · 2015Review
- Standardization of formulations for the acute amino acid depletion and loading tests.Journal of psychopharmacology (Oxford, England) · 2015Article
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
9 authors at 1 institution in 2 countries.
Funding
No grant is acknowledged in the PubMed record.
Abstract
rationaleIt has been reported that in panic disorder (PD), tryptophan depletion enhances the vulnerability to experimentally induced panic, while the administration of serotonin precursors blunts the response to challenges.
objectivesUsing a high-dose carbon dioxide (CO(2)) challenge, we aimed to investigate the effects of acute tryptophan depletion (ATD) and acute tryptophan loading (ATL) on CO(2)-induced panic response in healthy volunteers.
methodsEighteen healthy volunteers participated in a randomized, double-blind placebo-controlled study. Each subject received ATD, ATL, and a balanced condition (BAL) in separate days, and a double-breath 35% CO(2) inhalation 4.5 h after treatment. Tryptophan (Trp) manipulations were obtained adding 0 g (ATD), 1.21 g (BAL), and 5.15 g (ATL) of l-tryptophan to a protein mixture lacking Trp. Assessments consisted of a visual analogue scale for affect (VAAS) and panic symptom list. A separate analysis on a sample of 55 subjects with a separate-group design has also been performed to study the relationship between plasma amino acid levels and subjective response to CO(2).
resultsCO(2)-induced subjective distress and breathlessness were significantly lower after ATD compared to BAL and ATL (p < 0.05). In the separate-group analysis, ΔVAAS scores were positively correlated to the ratio Trp:ΣLNAA after treatment (r = 0.39; p < 0.05).
conclusionsThe present results are in line with preclinical data indicating a role for the serotonergic system in promoting the aversive respiratory sensations to hypercapnic stimuli (Richerson, Nat Rev Neurosci 5(6):449-461, 2004). The differences observed in our study, compared to previous findings in PD patients, might depend on an altered serotonergic modulatory function in patients compared to healthy subjects.
Indexed as
Identifiers
What OpenQuestion holds
Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.