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Chapter 44: Gut-Brain Interactions and Feeding Behaviors

You are performing laser ablation experiments on laboratory animals to ascertain the effects, on feeding behaviors, of damage to certain regions of the brain. In one series of experiments it is found that loss of the targeted brain region causes the animals eat nearly continuously, no matter the time of day, nor the composition of the chow. The ablation was centered on the hypothalamus and these results strongly indicate the damage affected which of the following regions of this structure?

A. lateral hypothalamic area (LHA)

B. nucleus of the solitary tract (NTS, NST)

C. paraventricular nucleus of the hypothalamus (PVN, PVH)

D. suprachiasmatic nucleus (SCN)

E. ventromedial hypothalamus (VMH, VMN)

Answer E: The hypothalamus is involved in control of feeding behavior as well as the secretion of various pituitary releasing hormones. Specific nuclei within the hypothalamus exert different effects on appetite and the desire for food. The ventromedial hypothalamic nucleus (VMH), and to a lesser extent the dorsomedial hypothalamic nucleus (DMH) is involved in the sensation of satiety and lesions in these regions of the hypothalamus result in hyperphagia (excessive hunger) and obesity.

You are assessing the effects of injecting synthetic peptides into laboratory mice. You discover that injecting one of the peptides induces hyperphagia. Which of the following hormones is most likely being mimicked by the actions of the synthetic peptide?

A. cholecystokinin, CCK

B. cocaine- and amphetamine-regulated transcript, CART

C. ghrelin

D. α-melanocyte stimulating hormone, α-MSH

E. peptide tyrosine tyrosine, PYY

Answer C: Ghrelin is produced and secreted by the X/A-like enteroendocrine cells of the stomach oxyntic (acid-secreting) glands. The major effect of ghrelin is exerted within the central nervous system at the level of the arcuate nucleus where it stimulates the release of neuropeptide Y (NPY) and agouti-related protein (AgRP). The actions of NPY and AgRP enhance appetite and thus, food intake.

Fatty acid metabolism within the brain is not a significant pathway for the generation of ATP. However, this does not mean that fatty acid metabolism is not a useful pathway in brain. Which of the following would be expected to be found at elevated levels in brain tissues following the metabolism of free fatty acids?

A. acetate

B. alanine

C....

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