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McMaster University
Life Sciences
Gautam Ullal

Depression February-05-13 7:50 PM - Two types of primary depression: 1. Endogenous: no external cause, all biological a. Treated via antidepressants 2. Reactive: caused by external factors, no biological basis a. Treat via CBT - Secondary depression is when you are depressed because you have another illness like schizophrenia Placebo vs. Fluoxetine in depression Experiment - In a double blind experiment with placebo and fluoxetine, both groups showed equal improvement in 6 weeks Results - PET scans showed increased activity in the PFC, PMC, anterior and posterior cingulate, posterior insula - And a decrease in subgenual cingulate, hypothalamus, parahippocampus and thalamus - But in fluoxetineonly the brain stem was increased and a decrease in hippocampal and striatal activity. Fluoxetine effects larger areas and causes stronger PET signals vs. placebo Theories 1. Fluoxetine works in a bottom-up cascade meaning it effects the cortex through the brain stem. Where as CBT or placebo works in top-down manner meaning it’s the cortex is effecting the lower brain areas Evidencefor theory1 - SRIs are used to treat depression, which increase the amount of serotonin available at a synaptic cleft. Which increases the synapses of serotonin, which supports the bottom-up cascade theory - By looking a PET scan we can see that the placebo seems to only function in the cortical areas, and fluoxetine works everywhere, but mainly in the brain steam (lower areas) 2. Monoamine theory of depression - Serotonin and Norepinephrine have to do a lot with emotions, by increasing them in concentration we can treat depression Adrenal Cortex vs. Adrenal Medulla in depression - There are two types of stress that can affect an individual 1. Chronic Stress: modulated by the HPA axis and takes a long time a. Stressor -> brain -> anterior pituitary -> adrenal cortex -> glucocorticoids 2. Acute stress: modulated by neuronal fast response a. SNS -> Adrenal Medulla -> Norepinephrine & Epinephrine 3. The adrenal glands sit on top of the kidneys and have layers. Each layer secretes a different hormone based on the type of stress HPA Axis - Whenever there is chronicstress CRH, ACTH and cortisol increase in concentration - Increase in these results in increased arousal, facilitate learning, provided there is not an over increase, to avoid an over expression of these hormones cor
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