The Effect of Tongue Exercise on Serotonergic Input to the Hypoglossal Nucleus in Young and Old Rats PurposeBreathing and swallowing problems affect elderly people and may be related to age-associated tongue dysfunction. Hypoglossal motoneurons that innervate the tongue receive a robust, excitatory serotonergic (5HT) input and may be affected by aging. We used a rat model of aging and progressive resistance tongue exercise to determine whether age-related ... Article
Article  |   June 01, 2012
The Effect of Tongue Exercise on Serotonergic Input to the Hypoglossal Nucleus in Young and Old Rats
 
Author Affiliations & Notes
  • Mary Behan
    University of Wisconsin–Madison
  • Adam E. Moeser
    University of Wisconsin–Madison
  • Cathy F. Thomas
    University of Wisconsin–Madison
  • John A. Russell
    University of Wisconsin–Madison
  • Hao Wang
    University of Wisconsin–Madison
  • Glen E. Leverson
    University of Wisconsin–Madison
  • Nadine P. Connor
    University of Wisconsin–Madison
  • Correspondence to Nadine Connor: connor@surgery.wisc.edu
  • Editor: Anne Smith
    Editor: Anne Smith×
  • Associate Editor: Jack Jiang
    Associate Editor: Jack Jiang×
Article Information
Speech
Article   |   June 01, 2012
The Effect of Tongue Exercise on Serotonergic Input to the Hypoglossal Nucleus in Young and Old Rats
Journal of Speech, Language, and Hearing Research, June 2012, Vol. 55, 919-929. doi:10.1044/1092-4388(2011/11-0091)
History: Received April 12, 2011 , Accepted October 13, 2011
 
Journal of Speech, Language, and Hearing Research, June 2012, Vol. 55, 919-929. doi:10.1044/1092-4388(2011/11-0091)
History: Received April 12, 2011; Accepted October 13, 2011
Web of Science® Times Cited: 5

PurposeBreathing and swallowing problems affect elderly people and may be related to age-associated tongue dysfunction. Hypoglossal motoneurons that innervate the tongue receive a robust, excitatory serotonergic (5HT) input and may be affected by aging. We used a rat model of aging and progressive resistance tongue exercise to determine whether age-related alterations in 5HT inputs to the hypoglossal nucleus can be modified. We hypothesized that tongue forces would increase with exercise, 5HT input to the tongue would decrease with age, and tongue exercise would augment 5HT input to the hypoglossal nucleus.

MethodYoung (9–10 months), middle-aged (24–25 months), and old (32–33 months) male F344/BN rats received tongue exercise for 8 weeks. Immunoreactivity for 5HT was measured in digital images of sections through the hypoglossal nucleus using ImageJ software.

ResultsTongue exercise resulted in increased maximum tongue forces at all ages. There was a statistically significant increase in 5HT immunoreactivity in the hypoglossal nucleus in exercised, young rats but only in the caudal third of the nucleus and primarily in the ventral half.

ConclusionSpecificity found in serotonergic input following exercise may reflect the topographic organization of motoneurons in the hypoglossal nucleus and the tongue muscles engaged in the exercise paradigm.

Acknowledgments
This study was supported by National Institutes of Health R01AG18760 (awarded to the first author) and R01DC008149 (awarded to the seventh author). We acknowledge Keith Kluender for consulting on the development of the animal training paradigm.
Order a Subscription
Pay Per View
Entire Journal of Speech, Language, and Hearing Research content & archive
24-hour access
This Article
24-hour access