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What are the key brain areas integrating neural and hormonal signals?

Dorsal vagal complex (nuclei of the solitary tract, dorsal motor nuclei of X, area postream)


prefrontal & orbitofrontal CTX


What is the role of the hypothalamic arcuate nucleus?

insulin and leptin release -
inhibit NPY/AgRP (Agouti-related peptide) neurons,
stimulate POMC (Pro-opio-melanocortin) neurons.


What is the net effect of leptin and insulin release?

The net effect is ‘anorexigenic’: reduced food intake, increased energy expenditure

Hormonal, behavioral responses mediated via neurons in the VMH, PVN and LH.


how does the body respond to body fat content?

negative feed back regulation of food

During weight gain, increased circulating leptin and insulin enhances the response to satiety signals and also diminishes perception of food reward.

The effect of weight loss to lower leptin and insulin levels increases rewarding properties of food while diminishing satiety.


What is the role of the mesocorticolimbic dopamine reward system?

Dopamine-depleted animals “like” food but “do not want” food

Lack motivation to seek food, but enjoy it when available

Stimulation of the dopamine axons
Craving for food without increasing the hedonic impact


What is the effect of serotonin hypothalamic serotonin levels?

Low: Postabsorptive period
Rise: In anticipation of food
Spike: During meals

Mood elevation - Rise in blood tryptophan and brain serotonin


What are drugs that elevate serotonin levels?

Example: Dexfenfluramine (Redux)- reduce appetite

antidepressants elevate serotonin levels

Disorders: Anorexia nervosa; Bulimia nervosa both often accompanied by depression
treat with antidepressants