HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 92/4/2198    most recent 00099.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (12) Citing Articles via Google Scholar Google Scholar Articles by Vazquez, J. Articles by Baghdoyan, H. A. Search for Related Content PubMed PubMed Citation Articles by Vazquez, J. Articles by Baghdoyan, H. A.

GABA_A Receptors Inhibit Acetylcholine Release in Cat Pontine Reticular Formation: Implications for REM Sleep Regulation

Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan 48109

Submitted 2 February 2004; accepted in final form 10 June 2004

This study used in vivo microdialysis in cat (n = 12) to test the hypothesis that gamma aminobutyric acid A (GABA_A) receptors in the pontine reticular formation (PRF) inhibit acetylcholine (ACh) release. Animals were anesthetized with halothane to hold arousal state constant. Six concentrations of the GABA_A receptor antagonist bicuculline (0.03, 0.1, 0.3, 1, 3, and 10 mM) were delivered to a dialysis probe in the PRF, and endogenously released ACh was collected simultaneously. Bicuculline caused a concentration dependent increase in ACh release (maximal increase = 345%; EC₅₀ = 1.3 mM; r² = 0.997). Co-administration of the GABA_A receptor agonist muscimol prevented the bicuculline-induced increase in ACh release. In a second series of experiments, the effects of bicuculline (0.1, 0.3, 1, and 3 mM) on ACh release were examined without the use of general anesthesia. States of wakefulness, rapid-eye-movement (REM) sleep, and non-REM sleep were identified polygraphically before and during dialysis delivery of bicuculline. Higher concentrations of bicuculline (1 and 3 mM) significantly increased ACh release during wakefulness (36%), completely suppressed non-REM sleep, and increased ACh release during REM sleep (143%). The finding that ACh release in the PRF is modulated by GABA_A receptors is consistent with the interpretation that inhibition of GABAergic transmission in the PRF contributes to the generation of REM sleep, in part, by increasing pontine ACh release.