Feeding Behaviour 11 Flashcards
What is set point theory?
Body mass and/or fat stores are maintained at a constant level. Homeostatic mechanisms exist to monitor energy stores and replace them when they are depleted
What happens to animals injected with NPY?
Begin feeding quicker, spent longer feeding and also ate more food
What is the lipostat hypothesis?
Fat must produce a metabolite that gives the brain information on the amount of body fat stores
What are the two mutations seen in lab mice? What behaviour does it cause?
Obese (ob/ob) and diabetes (db/db)
Both eat more than normal mice- hyperphagic
How was the parabiosis study carried out?
Parabiotic mice were surgically joined to share the same blood circulation
Wild type and ob ob
Wild type and db db
Ob ob and db db
What were the results from the parabiosis study?
Wild type ob ob: ob ob lost weight
Wild type db db: wild type lost weight
Ob ob and db db: ob ob lost weight
What’s the name of the obese protein that was discovered?
Leptin
How does Leptin affect NPY?
It partly or completely blocked the stimulation of food intake
Where was a Leptin receptor identified?
The choroid plexus in the brain where cerebrospinal fluid (CSF) is produced and also lateral ventricles
What makes db/db and fa/fa mice resistant to Leptin?
Shorter than normal receptors
What do NPY neurons also stimulate?
What do both do?
Agouti-related protein (AGRP)
Both stimulate food intake and promote weight gain
What do a second group of neurons co express?
What do the gene products do?
POMC and CART
Inhibit food intake and promote weight loss
What is the name of the inhibitory Neuropeptide encoded by the POMC gene?
Alpha-MSH
How does Leptin promote weight loss? (What is the process?)
It activates POMC/CART neurons resulting in secretion of alpha-MSH
Alpha-MSH binds to MC4R in paraventricular nucleus to inhibit feeding
What does AGRP act on?
Blocks alpha-MSH from binding to the MC4R
