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licking_to_io_sucrose.avi (12.83 MB)

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Brainstem Mechanisms Underlying Ingestion and Rejection

Chen, Zhixiong
http://rave.ohiolink.edu/etdc/view?acc_num=osu1041523002

Abstract Details

2003, Doctor of Philosophy, Ohio State University, Dentistry.
Feeding behavior is controlled by brain structures distributed in the cerebral cortex, limbic system and brainstem. In the brainstem, a central pattern generator (CPG) for mastication has been localized to the midline medullary reticular formation based on cortically induced rhythmic jaw movements (fictive mastication), or to the reticular formation (RF) between the trigeminal and facial motor nuclei based on chemically elicited rhythmic trigeminal discharge in a tissue slice preparation. Other studies, however, suggest a role for the lateral medullary RF in orchestrating ingestive oromotor activity. Direct behavioral evidence supporting the location of these CPGs, however, is lacking. Thus, the first study tested the hypothesis that the lateral medullary RF is essential for organizing oromotor patterns of ingestion and rejection. In the behaving rat, licking was induced by either intra-oral (IO) infusions of sucrose or saline, or sucrose presented in a bottle. Gaping (rejection) responses were elicited by IO delivery of quinine hydrochloride. All responses were measured electromyographically from the anterior digastric (jaw-opener) and geniohyoid (tongue-protruder) muscles. Inactivation of the lateral medullary RF with the GABAA agonist muscimol suppressed both licking and gaping. Infusions into other RF regions were ineffective, indicating an essential role for the lateral medullary RF. Because both excitatory and inhibitory amino acids (EAA, IAA) are involved in fictive mastication, we further examined whether they are also important for ingestive responses elicited by natural stimuli. In a second series of experiments, EAA and IAA antagonists were infused into the lateral medullary RF. It was found that (1) the lateral medullary RF is driven by glutamatergic inputs, mediated by both non-NMDA and NMDA receptors, (2) it is under tonic inhibition from GABAergic and glycinergic inputs, (3) this substrate is also involved in the suppression of eupnea that is mediated by non-NMDA receptors. These findings provide behavioral evidence to support the hypothesis that the lateral medullary RF is a multifunctional substrate that controls the oromotor nuclei to generate licking and gaping, and the oromotor components of gasping.
Joseph Travers (Advisor)
103 p.
Central pattern generator; NMDA receptor; Non-NMDA receptor; GABAA receptor; Glycine receptor; Taste oromotor processing

Recommended Citations

Citations

  • Chen, Z. (2003). Brainstem Mechanisms Underlying Ingestion and Rejection [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1041523002

    APA Style (7th edition)

  • Chen, Zhixiong. Brainstem Mechanisms Underlying Ingestion and Rejection. 2003. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1041523002.

    MLA Style (8th edition)

  • Chen, Zhixiong. "Brainstem Mechanisms Underlying Ingestion and Rejection." Doctoral dissertation, Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1041523002

    Chicago Manual of Style (17th edition)

osu1041523002
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This open access ETD is published by The Ohio State University and OhioLINK.