GABAergic neurons in prepositus hypoglossi regulate REM sleep by its action on locus coeruleus in freely moving rats

Synapse. 2001 Dec 1;42(3):141-50. doi: 10.1002/syn.1109.


GABA in locus coeruleus modulates REM sleep. Apart from the presence of interneurons, locus coeruleus also receives GABAergic inputs from prepositus hypoglossi in the medulla, where the presence of REM-ON-like neurons have been reported. Therefore, it was hypothesized that GABAergic projections from prepositus hypoglossi to locus coeruleus may modulate REM sleep. The experiments were conducted on chronic rats prepared for recording EEG, EOG, and EMG in freely moving conditions. Bipolar stimulating electrodes were implanted in prepositus hypoglossi bilaterally, while chemitrodes were implanted bilaterally in locus coeruleus. The prepositus hypoglossi were bilaterally stimulated (3 Hz, 250 microsec, 100 microA) for 8 h in the presence and absence of picrotoxin (0.25 microg/250 nl) microinjection bilaterally in locus coeruleus, followed by poststimulation recording for 4 h. It was observed that stimulation of prepositus hypoglossi alone significantly increased REM sleep primarily by increasing the REM sleep duration per episode. However, when it was stimulated in the presence of picrotoxin in LC, REM sleep decreased, predominantly due to decreased REM sleep duration per episode. The results of this study suggest that GABAergic inputs from prepositus hypoglossi act on locus coeruleus and regulate REM sleep, possibly by inhibition of REM-OFF neurons.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Central Nervous System Stimulants / pharmacology
  • Electric Stimulation
  • Locus Coeruleus / cytology
  • Locus Coeruleus / physiology*
  • Male
  • Medulla Oblongata / cytology
  • Medulla Oblongata / physiology*
  • Microinjections
  • Motor Activity
  • Neural Pathways
  • Neurons / drug effects
  • Neurons / physiology
  • Picrotoxin / pharmacology
  • Rats
  • Rats, Wistar
  • Sleep, REM / drug effects
  • Sleep, REM / physiology*
  • Wakefulness / drug effects
  • Wakefulness / physiology
  • gamma-Aminobutyric Acid / pharmacology
  • gamma-Aminobutyric Acid / physiology*


  • Central Nervous System Stimulants
  • Picrotoxin
  • gamma-Aminobutyric Acid