Increased GABAergic activity in the region of the pedunculopontine and deep mesencephalic reticular nuclei reduces REM sleep and impairs learning in rats.
Newly formed memories are initially fragile and require consolidation to be transformed into an enduring state. Memory consolidation may occur during increased postlearning REM sleep. REM deprivation during these periods (termed REM sleep windows [RSWs]) impairs subsequent performance. The pedunculopontine nucleus (PPT) and adjacent deep mesencephalic reticular nuclei (DpMe) have been implicated in the generation of REM sleep. Following 24-hr baseline recording, rats were trained on the 2-way avoidance task for 50 trials/day over 2 days and retested on Day 3. EEG was recorded 22 hr after training on training Days 1 and 2. Rats were injected with the GABAB agonist baclofen or saline into the PPT/DpMe region at 0300 to coincide with the start of a known RSW. Based on shuttle performance, saline rats were assigned post hoc to a learning group (LG) that avoided the footshock at least 60% at retest or nonlearning group (NLG) that performed below this criterion. Baclofen-injected rats were not assigned post hoc into separate groups as all rats performed below the learning criterion. PPN/DpMe infusions of the inhibitory GABAB agonist baclofen decreased REM and impaired subsequent memory performance. Normal GABAergic transmission in the PPN/DpMe may be necessary for REM to occur and for the consolidation of incentive learning.
Fogel
S M
SM
Centre for Neuroscience Studies, Queen's University.
Smith
C T
CT
Department of Psychology, Trent University.
Beninger
R J
RJ
Department of Psychology, Queen's University.
D000818:Animals; D001362:Avoidance Learning / Q000502:physiology; D001522:Behavior, Animal; D004569:Electroencephalography; D007859:Learning Disabilities / Q000209:etiology* / Q000378:metabolism; D008297:Male; D045042:Pedunculopontine Tegmental Nucleus / Q000293:injuries / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012154:Reticular Formation / Q000293:injuries / Q000378:metabolism*; D012895:Sleep, REM / Q000502:physiology*; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D005680:gamma-Aminobutyric Acid