μ-Opioid modulation in the rostral solitary nucleus and reticular formation alters taste reactivity: evidence for a

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Nicole R Kinzeler1, Susan P Travers

  • 1Department of Psychology, The Ohio State University, Columbus, Ohio, USA. kinzeler.2@osu.edu

American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
|June 24, 2011
PubMed

Insights

Activation of μ-opioid receptors (MORs) in the brainstem

Area of Science:

  • Neuroscience
  • Neurobiology
  • Feeding Behavior Research

Background:

  • Endogenous opioids and μ-opioid receptors (MORs) modulate feeding behavior.
  • Forebrain MOR activation enhances intake of palatable foods and taste palatability.
  • The role of MORs in brainstem taste processing remains unclear.

Purpose of the Study:

  • To investigate the effects of MOR activation in the rostral nucleus of the solitary tract (rNST) and dorsal reticular formation (RF) on oromotor responses.
  • To determine if MOR activation in the brainstem influences taste reactivity and consummatory behaviors.

Main Methods:

  • Rats were implanted with intraoral cannulas, electromyographic electrodes, and brain cannulas targeting the ventral rNST.
  • Licking and gaping responses to sucrose, water, and quinine were measured before and after infusions of a MOR agonist (Damgo) or saline.
  • Oromotor responses were analyzed for rate, amplitude, and bout size.

Main Results:

  • Damgo infusions into the rNST/dorsal RF altered lick and gape bout characteristics, slowing the rate, increasing amplitude, and decreasing bout size.
  • Neutral stimuli like water, typically eliciting licking, evoked gaping responses after Damgo administration.
  • These effects contrast with the facilitatory effects of MOR activation in the forebrain.

Conclusions:

  • μ-opioid receptor activation in the rNST/dorsal RF has complex, suppressive effects on oromotor responding.
  • Brainstem MOR signaling appears to inhibit, rather than facilitate, ingestion, contrasting with forebrain mechanisms.
  • This study reveals a differential role of MORs in taste processing within the central nervous system.

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