Correspondence

Inhibition of Food Intake by Peptide YY_3–36

N Engl J Med 2003; 349:2365-2366December 11, 2003

Article

To the Editor:

The insights provided by Korner and Leibel (Sept. 4 issue)1 into the interplay between the digestive and nervous systems are cogent, but the figure in their article seems to contain an error or, at least, an oversimplification. A neuron with a cell body that occupies the nucleus of the solitary tract is portrayed as the efferent innervation to the small intestine, according to the direction indicated by the adjacent arrow. Neurons of this type are not efferent, and they do not directly innervate the gut wall. Preganglionic parasympathetic outflow from the hindbrain to postganglionic autonomic neurons in the wall of the small intestine (i.e., efferent innervation) occurs by way of neurons with cell bodies that constitute the dorsal motor nucleus of the vagus nerve. The nucleus of the solitary tract receives afferent input from the small intestine by way of neurons with cell bodies that form the inferior vagal (nodose) ganglion. Neurons constituting the nucleus of the solitary tract are situated entirely within the brain.2,3 The figure in Korner and Leibel's article raises the question of exactly where peptide YY_3–36 acts on neurons associated with the hindbrain to exert its inhibitory effect.

Mark E. DeSantis, Ph.D.
University of Idaho, Moscow, ID 83844-4207

3 References

1. 1

   Korner J, Leibel RL. To eat or not to eat -- how the gut talks to the brain. N Engl J Med 2003;349:926-928
   Full Text | Web of Science | Medline

2. 2

   Kandel ER, Schwartz JH, Jessel TM, eds. Principles of neural science. 4th ed. New York: McGraw-Hill, 2000:960-81.
   

3. 3

   Wilson-Pauwels L, Akesson EJ, Stewart PA. Cranial nerves. Toronto: B.C. Decker, 1988:126-37.
   

Author/Editor Response

We appreciate the feedback from Dr. DeSantis about our figure, which depicts interactions among hormonal and neural pathways that regulate energy homeostasis. In this schematic diagram, we indicated that the nucleus of the solitary tract provides efferent innervation to the small intestine. Actually, the nucleus of the solitary tract is a mix of sensory neurons located within the dorsal vagal complex of the medulla. The dorsal vagal complex is a primary site of action of several neuropeptides mediating gastrointestinal activities; in addition, it contains efferent neurons that constitute the dorsal motor nucleus of the vagus. The effect of peptide YY_3–36 on gastric motility is mediated, at least in part, by direct inhibition of vagal efferent neurons in the dorsal motor nucleus through actions at Y₂-type peptide YY receptors.1 Thus, in addition to its effects within the arcuate nucleus of the hypothalamus, peptide YY_3–36 acts as an “ileal brake” that suppresses gastric motility, thereby possibly contributing to a sense of satiety.

Judith Korner, M.D., Ph.D.
Rudolph L. Leibel, M.D.
Columbia University, New York, NY 10032

1 References

1. 1

   Chen C-H, Rogers RC. Peptide YY and the Y2 agonist PYY-(13-36) inhibit neurons of the dorsal motor nucleus of the vagus. Am J Physiol 1997;273:R213-R218
   Web of Science | Medline