Stopped: Recruitment did not take place for this research due to several delays and then one of the PIs moved out of the country and the project was closed
PURPOSE The purpose of this study is to elucidate whether quetiapine fumurate (Seroquel) exerts its antidepressant activity in bipolar disorder through altering either serotonergic or catecholinergic activity. HYPOTHESIS By depleting either serotonin or catecholamines in successfully treated bipolar patients, relapse will be induced and reveal which neurotransmitters are effected when receiving normal treatment JUSTIFICATION While the exact mechanism of action of the classical antidepressants is not fully understood, strong evidence implicating serotonin and noradrenalin to be necessary (albeit insufficient) for the resolution of depression comes from neurotransmitter depletion studies. This biological evidence for each of these two neurotransmitters come from study paradigms in which the neurotransmitter (or its precursor) are selectively and effectively depleted from patients who have responded to antidepressants which either work through enhancing serotonin (for example, SRI antidepressants) or catecholamines (such as secondary amine tricyclics, Reboxetine, etc.). It has been shown, and replicated, that patients that respond to serotonin enhancing drugs precipitously and dramatically relapse when given a diet (often in the form of a milkshake) which is void of tryptophan, the precursor of serotonin. This diet often contains other long-chain amino acids to prevent any residual tryptophan in the system from entering the CNS. These patients who have then relapsed on the tryptophan-free diet have their tryptophan repleted and their mood improves often over a very short time frame (for example, five hours). When this technique is performed on patients responding to catecholamine-enhancing drugs there is no significant clinical effect. A similar approach can be taken with patients who respond to noradrelanine-enhancing drugs. Specifically, their catecholamine stores can be depleted by using dietary tyrosine. This reduces the synthesis of catecholamines and dopamine thus depleting pre-synaptic noradrenaline. For patients who responded to noradrenaline-enhancing drugs, this results in a relapse in terms of depressive symptomatology. When this dietary tyrosine strategy is applied to serotonin responders, there is no significant clinical effect.
Age range
19 Years – 65 Years
Sex
ALL
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To determine if a given depletion treatment induces relapse, measured as the mean HAM-D 17-item score of each group. A HAM-D score of 12 points or higher will be defined as relapse, measured 24-, 48- and 96-hours post-depletion.
Timeframe: 4 days