Biomedical subjects

Sjacko Sobczak

Publications and source records attributed to Sjacko Sobczak.

4 recordsLinked to original sources

PubMed2007

Sex differences in the effect of acute tryptophan depletion on declarative episodic memory: a pooled analysis of nine studies.

Acute tryptophan depletion (ATD) studies have shown that serotonin plays a role in learning and memory processes. In this study, we performed a pooled analysis of nine ATD studies in order to examine the nature of the memory-impairing effects of ATD and mediating factors, such as gender, age and vulnerability for disease in which disturbed serotonin was hypothesized to play a role. All studies that were used in this pooled analysis assessed declarative episodic memory using a verbal learning task paradigm. Immediate recall, delayed recall, and delayed recognition scores were examined. A total of 211 participants were included in the analysis. The analysis revealed that ATD impaired not only delayed recall, but also immediate recall. The ATD-induced impairments were larger in females than in males. Furthermore, ATD did not interact with any other serotonergic vulnerability and age. This suggests that the only factor that actually has the properties of a serotonergic vulnerability factor for declarative memory performance is female gender. The findings provide further support for a critical role of serotonin in declarative episodic memory.

Adolescent↗

PubMed2004

Acute tryptophan depletion slows gastric emptying in females.

Serotonin (5-HT) is an important neurotransmitter involved in the brain-gut axis. It is possible to lower the 5-HT level in the body by means of a nutritional intervention using an amino acid mixture; the acute tryptophan depletion (ATD) method. We studied the effect of ATD on gastric emptying in healthy females, who received both ATD and placebo in a random order. Gastric emptying was measured using the [(13)C]octanoic acid breath test. The present data demonstrate significant differences in both gastric emptying and lag phase (Tlag) between the ATD and placebo experiment. Eight out of ten subjects showed a delayed gastric emptying in the ATD experiment. Both the gastric half-emptying time (T1/2) and the Tlag were significantly higher in the ATD experiment. T1/2 in the ATD experiment was 137.2 (range 76.2-634.8) min; T1/2 for the placebo experiment was 98.5 (range 63.7-168.8) min (P=0.028). Tlag in the ATD experiment was 83.7 (range 45.1-356.2) min; Tlag for the placebo experiment was 56.9 (range 23.2-101.2) min (P=0.007). We conclude that lowering the 5-HT level in the body using the ATD method leads to a significantly delayed gastric emptying of a solid meal. Nutritional manipulation of the serotonergic system in healthy volunteers may lead to alterations in gastrointestinal motility.

Adult↗

PubMed2003

Tryptophan modulation and cognition.

The interest in the function of the serotonergic system in relation to cognition stems from three sources: (1) the association of depression, cognitive dysfunction and 5-HT dysregulation; (2) the association of drug-induced 5-HT dysregulation and cognitive dysfunction; and (3) the association of cognitive performance and serotonergic function per se. We performed several experiments in subjects at risk for cognitive impairment and in healthy volunteers, in which 5-HT was manipulated by means of either tryptophan depletion or tryptophan loading. The results show that tryptophan and cognitive performance are associated in a complex non-linear fashion. Dissociations are observed between cognitive functions: tryptophan depletion impairs memory consolidation but improves focussed attention; as well as between subject groups: tryptophan depletion impairs problem solving in healthy 1st degree relatives of bipolar depressed patients but improves it in healthy volunteers without such a family history. It was demonstrated that the mood- and memory effects of tryptophan-depletion were specifically mediated by the depletion of tryptophan and also that the observed memory and cognitive deficits were emotionally biased in a manner consistent with depressive symptoms. We conclude that experimental manipulations of tryptophan mediate temporal and frontal cognitive functions such as memory consolidation and working memory respectively, in an opposite manner.

Cognition↗

PubMed2002

Mood, prolactin and cortisol responses following intravenous L-tryptophan challenge: evidence for serotonergic vulnerability in first-degree relatives of bipolar patients.

Central serotonergic vulnerability indicated by altered mood and neuroendocrine responses to an intravenous (i.v.) tryptophan (Trp) challenge was assessed in healthy adult unaffected first-degree relatives of bipolar disorder (BD) patients (n = 30) (family history; FH). The effects of a single dose of 7.0 g Trp on mood, cortisol and prolactin (Prl) in FH subjects were compared with healthy matched controls (n = 15) in a placebo-controlled, double blind cross-over design. Prl and cortisol responses increased following Trp. Overall, Trp lowered mood. Hormonal and mood effects did not differ between FH and controls. Results show some evidence for differences in serotonergic vulnerability between relatives of type I BD patients and relatives of type II BD patients.

Adult↗